SUSE Linux Enterprise Server 11 SP3

Administration Guide

Publication Date 19 Jul 2013

Copyright © 2006–2013 SUSE LLC and contributors. All rights reserved.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or (at your option) version 1.3; with the Invariant Section being this copyright notice and license. A copy of the license version 1.2 is included in the section entitled GNU Free Documentation License.

For SUSE and Novell trademarks, see the Novell Trademark and Service Mark list http://www.novell.com/company/legal/trademarks/tmlist.html. All other third party trademarks are the property of their respective owners. A trademark symbol (®, ™ etc.) denotes a SUSE or Novell trademark; an asterisk (*) denotes a third party trademark.

All information found in this book has been compiled with utmost attention to detail. However, this does not guarantee complete accuracy. Neither SUSE LLC, its affiliates, the authors nor the translators shall be held liable for possible errors or the consequences thereof.


Contents

About This Guide
1. Available Documentation
2. Feedback
3. Documentation Conventions
I. Support and Common Tasks
1. YaST Online Update
1.1. The Online Update Dialog
1.2. Installing Patches
1.3. Automatic Online Update
2. Gathering System Information for Support
2.1. Overview
2.2. Collecting Information Using Supportconfig
2.3. Submitting Information to Novell
2.4. For More Information
3. YaST in Text Mode
3.1. Navigation in Modules
3.2. Restriction of Key Combinations
3.3. YaST Command Line Options
4. Snapshots/Rollback with Snapper
4.1. Requirements
4.2. Using Snapper to Undo System Changes
4.3. Manually Creating and Managing Snapshots
4.4. Limitations
4.5. Frequently Asked Questions
4.6. Using Snapper on Thin-Provisioned LVM Volumes
5. Remote Access with VNC
5.1. One-time VNC Sessions
5.2. Persistent VNC Sessions
6. Managing Software with Command Line Tools
6.1. Using Zypper
6.2. RPM—the Package Manager
7. Bash and Bash Scripts
7.1. What is The Shell?
7.2. Writing Shell Scripts
7.3. Redirecting Command Events
7.4. Using Aliases
7.5. Using Variables in Bash
7.6. Grouping And Combining Commands
7.7. Working with Common Flow Constructs
7.8. For More Information
II. System
8. 32-Bit and 64-Bit Applications in a 64-Bit System Environment
8.1. Runtime Support
8.2. Software Development
8.3. Software Compilation on Biarch Platforms
8.4. Kernel Specifications
9. Booting and Configuring a Linux System
9.1. The Linux Boot Process
9.2. The init Process
9.3. System Configuration via /etc/sysconfig
10. The Boot Loader GRUB
10.1. Booting with GRUB
10.2. Configuring the Boot Loader with YaST
10.3. Uninstalling the Linux Boot Loader
10.4. Creating Boot CDs
10.5. The Graphical SUSE Screen
10.6. Troubleshooting
10.7. For More Information
11. UEFI (Unified Extensible Firmware Interface)
11.1. Secure Boot
11.2. For More Information
12. Special System Features
12.1. Information about Special Software Packages
12.2. Virtual Consoles
12.3. Keyboard Mapping
12.4. Language and Country-Specific Settings
13. Printer Operation
13.1. The Workflow of the Printing System
13.2. Methods and Protocols for Connecting Printers
13.3. Installing the Software
13.4. Network Printers
13.5. Printing from the Command Line
13.6. Special Features in SUSE Linux Enterprise Server
13.7. Troubleshooting
14. Dynamic Kernel Device Management with udev
14.1. The /dev Directory
14.2. Kernel uevents and udev
14.3. Drivers, Kernel Modules and Devices
14.4. Booting and Initial Device Setup
14.5. Monitoring the Running udev Daemon
14.6. Influencing Kernel Device Event Handling with udev Rules
14.7. Persistent Device Naming
14.8. Files used by udev
14.9. For More Information
15. The X Window System
15.1. Manually Configuring the X Window System
15.2. Installing and Configuring Fonts
15.3. For More Information
16. Accessing File Systems with FUSE
16.1. Configuring FUSE
16.2. Available FUSE Plug-ins
16.3. For More Information
III. Mobile Computers
17. Mobile Computing with Linux
17.1. Laptops
17.2. Mobile Hardware
17.3. Cellular Phones and PDAs
17.4. For More Information
18. Wireless LAN
18.1. WLAN Standards
18.2. Operating Modes
18.3. Authentication
18.4. Encryption
18.5. Configuration with YaST
18.6. Tips and Tricks for Setting Up a WLAN
18.7. Troubleshooting
18.8. For More Information
19. Power Management
19.1. Power Saving Functions
19.2. Advanced Configuration and Power Interface (ACPI)
19.3. Rest for the Hard Disk
19.4. Troubleshooting
19.5. For More Information
20. Using Tablet PCs
20.1. Installing Tablet PC Packages
20.2. Configuring Your Tablet Device
20.3. Using the Virtual Keyboard
20.4. Rotating Your Display
20.5. Using Gesture Recognition
20.6. Taking Notes and Sketching with the Pen
20.7. Troubleshooting
20.8. For More Information
IV. Services
21. Basic Networking
21.1. IP Addresses and Routing
21.2. IPv6—The Next Generation Internet
21.3. Name Resolution
21.4. Configuring a Network Connection with YaST
21.5. NetworkManager
21.6. Configuring a Network Connection Manually
21.7. Setting Up Bonding Devices
21.8. smpppd as Dial-up Assistant
22. SLP Services in the Network
22.1. Installation
22.2. Activating SLP
22.3. SLP Front-Ends in SUSE Linux Enterprise Server
22.4. Installation over SLP
22.5. Providing Services via SLP
22.6. For More Information
23. Time Synchronization with NTP
23.1. Configuring an NTP Client with YaST
23.2. Manually Configuring NTP in the Network
23.3. Dynamic Time Synchronization at Runtime
23.4. Setting Up a Local Reference Clock
23.5. Clock Synchronization to an External Time Reference (ETR)
24. The Domain Name System
24.1. DNS Terminology
24.2. Installation
24.3. Configuration with YaST
24.4. Starting the BIND Name Server
24.5. The /etc/named.conf Configuration File
24.6. Zone Files
24.7. Dynamic Update of Zone Data
24.8. Secure Transactions
24.9. DNS Security
24.10. For More Information
25. DHCP
25.1. Configuring a DHCP Server with YaST
25.2. DHCP Software Packages
25.3. The DHCP Server dhcpd
25.4. For More Information
26. Using NetworkManager
26.1. Use Cases for NetworkManager
26.2. Enabling or Disabling NetworkManager
26.3. Configuring Network Connections
26.4. Using KNetworkManager
26.5. Using GNOME NetworkManager Applet
26.6. NetworkManager and VPN
26.7. NetworkManager and Security
26.8. Frequently Asked Questions
26.9. Troubleshooting
26.10. For More Information
27. Samba
27.1. Terminology
27.2. Starting and Stopping Samba
27.3. Configuring a Samba Server
27.4. Configuring Clients
27.5. Samba as Login Server
27.6. Samba Server in the Network with Active Directory
27.7. For More Information
28. Sharing File Systems with NFS
28.1. Terminology
28.2. Installing NFS Server
28.3. Configuring NFS Server
28.4. Configuring Clients
28.5. For More Information
29. File Synchronization
29.1. Available Data Synchronization Software
29.2. Determining Factors for Selecting a Program
29.3. Introduction to CVS
29.4. Introduction to rsync
29.5. For More Information
30. The Apache HTTP Server
30.1. Quick Start
30.2. Configuring Apache
30.3. Starting and Stopping Apache
30.4. Installing, Activating, and Configuring Modules
30.5. Getting CGI Scripts to Work
30.6. Setting Up a Secure Web Server with SSL
30.7. Avoiding Security Problems
30.8. Troubleshooting
30.9. For More Information
31. Setting up an FTP Server with YaST
31.1. Starting the FTP Server
31.2. FTP General Settings
31.3. FTP Performance Settings
31.4. Authentication
31.5. Expert Settings
31.6. For More Information
32. The Squid Proxy Server
32.1. Some Facts about Proxy Caches
32.2. System Requirements
32.3. Starting Squid
32.4. The /etc/squid/squid.conf Configuration File
32.5. Configuring a Transparent Proxy
32.6. cachemgr.cgi
32.7. squidGuard
32.8. Cache Report Generation with Calamaris
32.9. For More Information
33. Web Based Enterprise Management Using SFCB
33.1. Introduction and Basic Concept
33.2. Setting up SFCB
33.3. SFCB CIMOM Configuration
33.4. Advanced SFCB Tasks
33.5. For More Information
V. Troubleshooting
34. Help and Documentation
34.1. Documentation Directory
34.2. Man Pages
34.3. Info Pages
34.4. Online Resources
35. Common Problems and Their Solutions
35.1. Finding and Gathering Information
35.2. Installation Problems
35.3. Boot Problems
35.4. Login Problems
35.5. Network Problems
35.6. Data Problems
35.7. IBM System z: Using initrd as a Rescue System
A. An Example Network
B. GNU Licenses
B.1. GNU Free Documentation License

List of Figures

1.1. YaST Online Update—Qt Interface
1.2. YaST Online Update—GTK Interface
3.1. Main Window of YaST in Text Mode
3.2. The Software Installation Module
9.1. System Services (Runlevel)
9.2. System Configuration Using the sysconfig Editor
10.1. Boot Loader Settings
11.1. UEFI: Secure Boot Process
17.1. Integrating a Mobile Computer in an Existing Environment
18.1. YaST: Configuring the Wireless Network Card
20.1. xvkbd Virtual Keyboard
20.2. Gesture Recognition with CellWriter
20.3. Annotating a PDF with Xournal
20.4. Editing Texts with Dasher
21.1. Simplified Layer Model for TCP/IP
21.2. TCP/IP Ethernet Packet
21.3. Configuring Network Settings
21.4. Modem Configuration
21.5. ISDN Configuration
21.6. ISDN Interface Configuration
21.7. DSL Configuration
23.1. YaST: NTP Server
23.2. Advanced NTP Configuration: Security Settings
24.1. DNS Server Installation: Forwarder Settings
24.2. DNS Server Installation: DNS Zones
24.3. DNS Server Installation: Finish Wizard
24.4. DNS Server: Logging
24.5. DNS Server: Zone Editor (Basics)
24.6. DNS Server: Zone Editor (NS Records)
24.7. DNS Server: Zone Editor (MX Records)
24.8. DNS Server: Zone Editor (SOA)
25.1. DHCP Server: Card Selection
25.2. DHCP Server: Global Settings
25.3. DHCP Server: Dynamic DHCP
25.4. DHCP Server: Start-Up
25.5. DHCP Server: Host Management
25.6. DHCP Server: Chroot Jail and Declarations
25.7. DHCP Server: Selecting a Declaration Type
25.8. DHCP Server: Configuring Subnets
25.9. DHCP Server: TSIG Configuration
25.10. DHCP Server: Interface Configuration for Dynamic DNS
25.11. DHCP Server: Network Interface and Firewall
26.1. GNOME Network Connections Dialog
26.2. KDE Network Configuration Dialog
26.3. KNetworkManager—Configured and Available Connections
27.1. Determining Windows Domain Membership
28.1. NFS Server Configuration Tool
28.2. Exporting Directories with NFSv2 and v3
30.1. HTTP Server Wizard: Default Host
30.2. HTTP Server Wizard: Summary
30.3. HTTP Server Configuration: Listen Ports and Addresses
30.4. HTTP Server Configuration: Server Modules
31.1. FTP Server Configuration — Start-Up
33.1. Package Selection for Web-Based Enterprise Management Pattern
33.2. Package selection of additional CIM providers
35.1. Checking Media
35.2. Displaying Hardware Information
35.3. US Keyboard Layout
35.4. Automatic Repair Mode

List of Tables

6.1. The Most Important RPM Query Options
6.2. RPM Verify Options
7.1. Bash Configuration Files for Login Shells
7.2. Bash Configuration Files for Non-Login Shells
7.3. Special Files for Bash
7.4. Overview of a Standard Directory Tree
7.5. Useful Environment Variables
9.1. Available Runlevels
9.2. Possible init Script Options
10.1. Screen Resolution and Color Depth Reference
12.1. ulimit: Setting Resources for the User
15.1. Sections in /etc/X11/xorg.conf
15.2. Parameters of fc-list
16.1. Available FUSE Plug-ins
17.1. Use Cases for NetworkManager
18.1. Overview of Various WLAN Standards
21.1. Several Protocols in the TCP/IP Protocol Family
21.2. Specific Addresses
21.3. Private IP Address Domains
21.4. Various IPv6 Prefixes
21.5. Manual Network Configuration Scripts
21.6. Parameters for /etc/host.conf
21.7. Databases Available via /etc/nsswitch.conf
21.8. Configuration Options for NSS Databases
21.9. Some Start-Up Scripts for Network Programs
29.1. Features of the File Synchronization Tools: -- = very poor, - = poor or not available, o = medium, + = good, ++ = excellent, x = available
33.1. Commands for Managing sfcbd
34.1. Man Pages—Categories and Descriptions
35.1. Log Files
35.2. System Information With the /proc File System
35.3. System Information With the /sys File System

List of Examples

4.1. Example time line configuration
6.1. Zypper—List of Known Repositories
6.2. rpm -q -i wget
6.3. Script to Search for Packages
7.1. A Shell Script Printing a Text
9.1. A Minimal INIT INFO Block
12.1. Entry in /etc/crontab
12.2. /etc/crontab: Remove Time Stamp Files
12.3. Example for /etc/logrotate.conf
12.4. ulimit: Settings in ~/.bashrc
13.1. /etc/modprobe.conf: Interrupt Mode for the First Parallel Port
13.2. Error Message from lpd
13.3. Broadcast from the CUPS Network Server
14.1. Example udev Rules
15.1. Screen Section of the File /etc/X11/xorg.conf
21.1. Writing IP Addresses
21.2. Linking IP Addresses to the Netmask
21.3. Sample IPv6 Address
21.4. IPv6 Address Specifying the Prefix Length
21.5. /etc/resolv.conf
21.6. /etc/hosts
21.7. /etc/networks
21.8. /etc/host.conf
21.9. /etc/nsswitch.conf
21.10. Output of the Command ping
21.11. Output of the ifconfig Command
21.12. Output of the route -n Command
24.1. Forwarding Options in named.conf
24.2. A Basic /etc/named.conf
24.3. Entry to Disable Logging
24.4. Zone Entry for example.com
24.5. Zone Entry for example.net
24.6. The /var/lib/named/example.com.zone File
24.7. Reverse Lookup
25.1. The Configuration File /etc/dhcpd.conf
25.2. Additions to the Configuration File
27.1. A CD-ROM Share (deactivated)
27.2. [homes] Share
27.3. Global Section in smb.conf
30.1. Variations of Name-Based VirtualHost Entries
30.2. Name-Based VirtualHost Directives
30.3. IP-Based VirtualHost Directives
30.4. Basic VirtualHost Configuration
30.5. VirtualHost CGI Configuration
32.1. Firewall Configuration: Option 15
32.2. Access Rules
32.3. Access Rules
35.1. Output of the Mount Command
35.2. chroot to the Mounted File System
35.3. Installing the IPL Record with zipl
35.4. Unmounting the File System

About This Guide

This guide is intended for use by professional network and system administrators during the operation of SUSE® Linux Enterprise. As such, it is solely concerned with ensuring that SUSE Linux Enterprise is properly configured and that the required services on the network are available to allow it to function properly as initially installed. This guide does not cover the process of ensuring that SUSE Linux Enterprise offers proper compatibility with your enterprise's application software or that its core functionality meets those requirements. It assumes that a full requirements audit has been done and the installation has been requested or that a test installation, for the purpose of such an audit, has been requested.

This guide contains the following:

Support and Common Tasks

SUSE Linux Enterprise offers a wide range of tools to customize various aspects of the system. This part introduces a few of them. A breakdown of available device technologies, high availability configurations, and advanced administration possibilities introduces the system to the administrator.

System

Learn more about the underlying operating system by studying this part. SUSE Linux Enterprise supports a number of hardware architectures and you can use this to adapt your own applications to run on SUSE Linux Enterprise. The boot loader and boot procedure information assists you in understanding how your Linux system works and how your own custom scripts and applications may blend in with it.

Mobile Computers

Laptops, and the communication between mobile devices like PDAs, or cellular phones and SUSE Linux Enterprise need some special attention. Take care for power conservation and for the integration of different devices into a changing network environment. Also get in touch with the background technologies that provide the needed functionality.

Services

SUSE Linux Enterprise is designed to be a network operating system. It offers a wide range of network services, such as DNS, DHCP, Web, proxy, and authentication services, and integrates well into heterogeneous environments including MS Windows clients and servers.

Troubleshooting

Provides an overview of where to find help and additional documentation in case you need more information or want to perform specific tasks with your system. Also find a compilation of the most frequent problems and annoyances and learn how to solve these issues on your own.

Many chapters in this manual contain links to additional documentation resources. This includes additional documentation that is available on the system as well as documentation available on the Internet.

For an overview of the documentation available for your product and the latest documentation updates, refer to http://www.suse.com/doc.

1. Available Documentation

We provide HTML and PDF versions of our books in different languages. The following manuals for users and administrators are available for this product:

Deployment Guide (↑Deployment Guide)

Shows how to install single or multiple systems and how to exploit the product inherent capabilities for a deployment infrastructure. Choose from various approaches, ranging from a local installation or a network installation server to a mass deployment using a remote-controlled, highly-customized, and automated installation technique.

Administration Guide

Covers system administration tasks like maintaining, monitoring, and customizing an initially installed system.

Security Guide (↑Security Guide)

Introduces basic concepts of system security, covering both local and network security aspects. Shows how to make use of the product inherent security software like AppArmor (which lets you specify per program which files the program may read, write, and execute), and the auditing system that reliably collects information about any security-relevant events.

Security and Hardening Guide (↑Security and Hardening Guide)

Deals with the particulars of installing and setting up a secure SUSE Linux Enterprise Server, and additional post-installation processes required to further secure and harden that installation. Supports the administrator with security-related choices and decisions.

System Analysis and Tuning Guide (↑System Analysis and Tuning Guide)

An administrator's guide for problem detection, resolution and optimization. Find how to inspect and optimize your system by means of monitoring tools and how to efficiently manage resources. Also contains an overview of common problems and solutions, and of additional help and documentation resources.

Virtualization with Xen (↑Virtualization with Xen)

Offers an introduction to virtualization technology of your product. It features an overview of the various fields of application and installation types of each of the platforms supported by SUSE Linux Enterprise Server as well as a short description of the installation procedure.

Virtualization with KVM for IBM System z (↑Virtualization with KVM for IBM System z)

Offers an introduction to setting up and managing virtualization with KVM (Kernel-based Virtual Machine) on SUSE Linux Enterprise Server. Learn how to manage KVM with libvirt or QEMU. The guide also contains detailed information about requirements, limitations, and support status.

AutoYaST (↑AutoYaST)

AutoYaST is a system for installing one or more SUSE Linux Enterprise systems automatically and without user intervention, using an AutoYaST profile that contains installation and configuration data. The manual guides you through the basic steps of auto-installation: preparation, installation, and configuration.

Storage Administration Guide (↑Storage Administration Guide)

Provides information about how to manage storage devices on a SUSE Linux Enterprise Server.

In addition to the comprehensive manuals, several quick start guides are available:

Installation Quick Start (↑Installation Quick Start)

Lists the system requirements and guides you step-by-step through the installation of SUSE Linux Enterprise Server from DVD, or from an ISO image.

Linux Audit Quick Start

Gives a short overview how to enable and configure the auditing system and how to execute key tasks such as setting up audit rules, generating reports, and analyzing the log files.

AppArmor Quick Start

Helps you understand the main concepts behind AppArmor®.

Virtualization with Linux Containers (LXC) (↑Virtualization with Linux Containers (LXC))

Gives a short introduction to LXC (a lightweight virtualization method) and shows how to set up an LXC host and LXC containers.

Find HTML versions of most product manuals in your installed system under /usr/share/doc/manual or in the help centers of your desktop. Find the latest documentation updates at http://www.suse.com/doc where you can download PDF or HTML versions of the manuals for your product.

2. Feedback

Several feedback channels are available:

Bugs and Enhancement Requests

For services and support options available for your product, refer to http://www.suse.com/support/.

To report bugs for a product component, log in to the Novell Customer Center from http://www.suse.com/support/ and select My Support+Service Request.

User Comments

We want to hear your comments about and suggestions for this manual and the other documentation included with this product. Use the User Comments feature at the bottom of each page in the online documentation or go to http://www.suse.com/doc/feedback.html and enter your comments there.

Mail

For feedback on the documentation of this product, you can also send a mail to doc-team@suse.de. Make sure to include the document title, the product version, and the publication date of the documentation. To report errors or suggest enhancements, provide a concise description of the problem and refer to the respective section number and page (or URL).

3. Documentation Conventions

The following typographical conventions are used in this manual:

  • /etc/passwd: directory names and filenames

  • placeholder: replace placeholder with the actual value

  • PATH: the environment variable PATH

  • ls, --help: commands, options, and parameters

  • user: users or groups

  • Alt, Alt+F1: a key to press or a key combination; keys are shown in uppercase as on a keyboard

  • File, File+Save As: menu items, buttons

  • ►amd64 em64t ipf: This paragraph is only relevant for the architectures amd64, em64t, and ipf. The arrows mark the beginning and the end of the text block.

    ►ipseries zseries: This paragraph is only relevant for the architectures System z and ipseries. The arrows mark the beginning and the end of the text block.

  • Dancing Penguins (Chapter Penguins, ↑Another Manual): This is a reference to a chapter in another manual.

Part I. Support and Common Tasks

Chapter 1. YaST Online Update

Novell offers a continuous stream of software security updates for your product. By default, the update applet is used to keep your system up-to-date. Refer to Section “Keeping the System Up-to-date” (Chapter 9, Installing or Removing Software, ↑Deployment Guide) for further information on the update applet. This chapter covers the alternative tool for updating software packages: YaST Online Update.

The current patches for SUSE® Linux Enterprise Server are available from an update software repository. If you have registered your product during the installation, an update repository is already configured. If you have not registered SUSE Linux Enterprise Server, you can do so by running Software+Online Update Configuration in YaST and start Advanced+Register for Support and Get Update Repository. Alternatively, you can manually add an update repository from a source you trust. To add or remove repositories, start the Repository Manager with Software+Software Repositories in YaST. Learn more about the Repository Manager in Section “Managing Software Repositories and Services” (Chapter 9, Installing or Removing Software, ↑Deployment Guide).

[Note]Error on Accessing the Update Catalog

If you are not able to access the update catalog, this might be due to an expired subscription. Normally, SUSE Linux Enterprise Server comes with a one or three years subscription, during which you have access to the update catalog. This access will be denied once the subscription ends.

In case of an access denial to the update catalog you will see a warning message with a recommendation to visit the Novell Customer Center and check your subscription. The Novell Customer Center is available at http://www.novell.com/center/.

Novell provides updates with different relevance levels:

Security Updates

Fix severe security hazards and should definitely be installed.

Recommended Updates

Fix issues that could compromise your computer.

Optional Updates

Fix non-security relevant issues or provide enhancements.

1.1. The Online Update Dialog

The YaST Online Update dialog is available in two toolkit flavors: GTK (for GNOME) and Qt (for KDE). Both interfaces differ in look and feel but basically provide the same functions. The following sections provide a brief description of each. To open the dialog, start YaST and select Software +Online Update. Alternatively, start it from the command line with yast2 online_update.

1.1.1. KDE Interface (Qt)

The Online Update window consists of four sections.

Figure 1.1. YaST Online Update—Qt Interface

YaST Online Update—Qt Interface

The Summary section on the left lists the available patches for SUSE Linux Enterprise Server. The patches are sorted by security relevance: security, recommended, and optional. You can change the view of the Summary section by selecting one of the following options from Show Patch Category:

Needed Patches (default view)

Non-installed patches that apply to packages installed on your system.

Unneeded Patches

Patches that either apply to packages not installed on your system, or patches that have requirements which have already have been fulfilled (because the relevant packages have already been updated from another source).

All Patches

All patches available for SUSE Linux Enterprise Server.

Each list entry in the Summary section consists of a symbol and the patch name. For an overview of the possible symbols and their meaning, press Shift+F1. Actions required by Security and Recommended patches are automatically preset. These actions are Autoinstall, Autoupdate and Autodelete.

If you install an up-to-date package from a repository other than the update repository, the requirements of a patch for this package may be fulfilled with this installation. In this case a check mark is displayed in front of the patch summary. The patch will be visible in the list until you mark it for installation. This will in fact not install the patch (because the package already is up-to-date), but mark the patch as having been installed.

Select an entry in the Summary section to view a short Patch Description at the bottom left corner of the dialog. The upper right section lists the packages included in the selected patch (a patch can consist of several packages). Click an entry in the upper right section to view details about the respective package that is included in the patch.

1.1.2. GNOME Interface (GTK)

The Online Update window consists of four main sections.

Figure 1.2. YaST Online Update—GTK Interface

YaST Online Update—GTK Interface

The upper right section lists the available (or already installed) patches for SUSE Linux Enterprise Server. To filter patches according to their security relevance, click the corresponding Priority entry in the upper left section of the window: Security, Recommended, Optional or All patches.

If all available patches are already installed, the Package listing in the upper right section will show no entries. The box in the bottom left-hand section shows the number of both available and already installed patches and lets you toggle the view to either Available or Installed patches.

Select an entry in the Package listing section to view a patch description and further details at the bottom right corner of the dialog. As a patch can consist of several packages, click the Applies to entry in the lower right section to see which packages are included in the respective patch.

Click on a patch entry to open a row with detailed information about the patch in the bottom of the window. Here you can see a detailed patch description as well as the versions available. You can also choose to Install optional patches—security and recommended patches are already preselected for installation.

1.2. Installing Patches

The YaST Online Update dialog allows you to either install all available patches at one go or to manually select the patches that you want to apply to your system. You may also revert patches that have been applied to the system.

By default, all new patches (except the optional ones) that are currently available for your system are already marked for installation. They will be applied automatically once you click Accept or Apply.

Procedure 1.1. Applying Patches with YaST Online Update

  1. Start YaST and select Software+Online Update.

  2. To automatically apply all new patches (except the optional ones) that are currently available for your system, proceed with Apply or Accept to start the installation of the preselected patches.

  3. To first modify the selection of patches that you want to apply:

    1. Use the respective filters and views the GTK and Qt interfaces provide. For details, refer to Section 1.1.1, “KDE Interface (Qt)” and Section 1.1.2, “GNOME Interface (GTK)”.

    2. Select or deselect patches according to your needs and wishes by activating or deactivating the respective check box (GNOME) or by right-clicking the patch and choosing the respective action from the context menu (KDE).

      [Important]Always Apply Security Updates

      However, do not deselect any security-related patches if you do not have a very good reason for doing so. They fix severe security hazards and prevent your system from exploits.

    3. Most patches include updates for several packages. If you want to change actions for single packages, right-click a package in the package view and choose an action (KDE).

    4. To confirm your selection and to apply the selected patches, proceed with Apply or Accept.

  4. After the installation is complete, click Finish to leave the YaST Online Update. Your system is now up-to-date.

[Tip]Disabling deltarpms

By default updates are downloaded as deltarpms. Since rebuilding rpm packages from deltarpms is a memory and CPU time consuming task, certain setups or hardware configurations might require you to disable the usage of deltarpms for performance sake.

To disable the use of deltarpms edit the file /etc/zypp/zypp.conf and set download.use_deltarpm to false.

1.3. Automatic Online Update

YaST also offers the possibility to set up an automatic update with daily, weekly or monthly schedule. To use the respective module, you need to install the yast2-online-update-configuration package first.

Procedure 1.2. Configuring the Automatic Online Update

  1. After installation, start YaST and select Software+Online Update Configuration.

    Alternatively, start the module with yast2 online_update_configuration from the command line.

  2. Activate Automatic Online Update.

  3. Choose whether to update Daily, Weekly, or Monthly.

    Some patches, such as kernel updates or packages requiring license agreements, require user interaction, which would cause the automatic update procedure to stop.

  4. Select if you want to Skip Interactive Patches in case you want the update procedure to proceed fully automatically.

    [Important]Skipping Patches

    If you select to skip any packages that require interaction, run a manual Online Update from time to time in order to install those patches, too. Otherwise you might miss important patches.

  5. To automatically accept any license agreements, activate Agree with Licenses.

  6. To automatically install all packages recommended by updated packages, activate Include Recommended Packages.

  7. To filter the patches by category (such as security or recommended), activate Filter by Category and add the appropriate patch categories from the list. Only patches of the selected categories will be installed. Others will be skipped.

  8. Confirm your configuration with OK.

Chapter 2. Gathering System Information for Support

Abstract

In case of problems, a system report may be created using the supportconfig command. This tool will collect information about the system such as: current kernel version, hardware, installed packages, partition setup and much more. This report will help Novell Technical Services to assist or locate the issue you reported. The command is provided by the package supportutils which is installed by default.

2.1. Overview

Novell Support Link (NSL) is new to SUSE Linux Enterprise Server. It is a tool that gathers system information and allows you to upload the collected data to another server for further analysis.

There are two ways to use Novell Support Link:

  1. Use the YaST Support module.

  2. Use the command line utility supportconfig.

The YaST Support module calls supportconfig to gather system information.

2.2. Collecting Information Using Supportconfig

The following sections describe how to use supportconfig with YaST, with the command line and what other options you have.

2.2.1. Using YaST

To use YaST to gather your system information, proceed as follows:

  1. Open the URL http://www.novell.com/center/eservice and create a service request number.

  2. Start YaST.

  3. Open the Support module.

  4. Click on Create report tarball.

  5. Select an option from the radio button list. If you want to test it first, use Only gather a minimum amount of info. Proceed with Next.

  6. Enter your contact information. Use your service request number from Step 1 and enter it into the text field labeled Novell 11 digit service request number. Proceed with Next.

  7. The information gathering begins. After the process is finished, continue with Next.

  8. Review the data collection. Continue with Next.

  9. Save your tarball. If you want to upload to the Novell customer center, make sure Upload log files tarball into URL is activated. Finish the operation with Next.

2.2.2. Using Supportconfig Directly

To use supportconfig from the command line, proceed as follows:

  1. Open a shell and become root.

  2. Run supportconfig without any options. This gathers the default system information.

  3. Wait for the tool to complete the operation.

  4. The default archive location is /var/log with the filename format nts_HOST_DATE_TIME.tbz

2.2.3. Common Supportconfig Options

The supportconfig utility is usually called without any options. Display a list of all options with supportconfig --help or refer to the man page. The following list gives a brief overview of the more common cases:

  • Use the minimal option (-m) to reduce the size of the information being gathered:

    supportconfig -m
  • Include additional contact information in the output (in one line):

    supportconfig -E tux@example.org -N "Tux Penguin" -O "Penguin Inc." ...
  • While troubleshooting a problem, you may want to gather information only about the area of the problem you are currently working on. For example, if you have problems with LVM, and recently found the problem with the default supportconfig output. After making changes, you want to gather the current LVM information. The following would gather the minimum supportconfig information and LVM only.

    supportconfig -i LVM

    To see a complete feature list, run:

    supportconfig -F

    If you need the opposite, exclude an area with the -x option. Both options, -i and -x, can be combined.

  • Collect already rotated log files. This is especially useful in high logging environments or after a kernel crash when syslog rotates the logs after a reboot.

    supportconfig -l

2.3. Submitting Information to Novell

You can use the YaST Support module or the supportconfig command line utility to submit system information to Novell. When you experience a server issue and would like Novell's assistance, you will need to open a service request and submit your server information to Novell. Both YaST and command line methods are described.

[Note]Privacy Statement

Novell treats system reports as confidental data. Please see our privacy commitment for details at http://www.novell.com/company/legal/privacy/.

Procedure 2.1. Submitting Information to Novell with YaST

  1. Open the URL http://www.novell.com/center/eservice and create a service request number.

  2. Write down your 11 digit service request number. The following examples will assume the service request number is 12345678901.

  3. Click on Create report tarball in the YaST Support module window.

  4. Select the Use custom radio button. Proceed with Next.

  5. Enter your contact information, fill in Novell 11 digit service request number and include Novell's upload target URL.

    Proceed with Next. Information gathering starts. After the process is finished, continue with Next.

  6. Review the data collection and use Remove from Data to remove any files you want excluded from the tarball uploaded to Novell. Continue with Next.

  7. By default, a copy of the tarball will be saved in /root. Confirm you are using one of the Novell upload targets described above and the Upload log files tarball into URL is activated. Finish with Next.

  8. Click Finish.

Procedure 2.2. Submitting Information to Novell with supportconfig

  1. Open the URL http://www.novell.com/center/eservice and create a service request number.

  2. Write down your 11 digit service request number. The following examples will assume the service request number is 12345678901.

  3. Servers with Internet connectivity:

    1. To use the default upload target, run:

      supportconfig -ur 12345678901
    2. For the secure upload target, use the following on one line:

      supportconfig -r 12345678901 -U  'https://secure-www.novell.com/upload?appname=supportconfig&file={tarball}'
  4. Servers without Internet connectivity

    1. Run the following:

      supportconfig -r 12345678901
    2. Manually upload the /var/log/nts_SR12345678901*tbz tarball to our FTP server (US customers use ftp://ftp.novell.com/incoming; Europe, the Middle East, and Africa use ftp://support-ftp.suse.com/in).

    3. You can also attach the tarball to your service request using the service request URL: http://www.novell.com/center/eservice.

  5. Once the tarball is in the incoming directory of our FTP server, it becomes automatically attached to your service request.

2.4. For More Information

Find more information about gathering system information in the following documents:

Chapter 3. YaST in Text Mode

This section is intended for system administrators and experts who do not run an X server on their systems and depend on the text-based installation tool. It provides basic information about starting and operating YaST in text mode.

YaST in text mode uses the ncurses library to provide an easy pseudo-graphical user interface. The ncurses library is installed by default. The minimum supported size of the terminal emulator in which to run YaST is 80x25 characters.

Figure 3.1. Main Window of YaST in Text Mode

Main Window of YaST in Text Mode

When you start YaST in text mode, the YaST Control Center appears (see Figure 3.1). The main window consists of three areas. The left frame features the categories to which the various modules belong. This frame is active when YaST is started and therefore it is marked by a bold white border. The active category is highlighted. The right frame provides an overview of the modules available in the active category. The bottom frame contains the buttons for Help and Quit.

When you start the YaST Control Center, the category Software is selected automatically. Use and to change the category. To select a module from the category, activate the right frame with and then use and to select the module. Keep the arrow keys pressed to scroll through the list of available modules. The selected module is highlighted. Press Enter to start the active module.

Various buttons or selection fields in the module contain a highlighted letter (yellow by default). Use Alt-highlighted_letter to select a button directly instead of navigating there with Tab. Exit the YaST Control Center by pressing Alt-Q or by selecting Quit and pressing Enter.

[Tip]Refreshing YaST Dialog Window

If a YaST dialog window gets corrupted or distorted (e.g., while resizing the window), press Ctrl-L to refresh and restore its contents.

3.1. Navigation in Modules

The following description of the control elements in the YaST modules assumes that all function keys and Alt key combinations work and are not assigned to different global functions. Read Section 3.2, “Restriction of Key Combinations” for information about possible exceptions.

Navigation among Buttons and Selection Lists

Use Tab to navigate among the buttons and frames containing selection lists. To navigate in reverse order, use Alt-Tab or Shift-Tab combinations.

Navigation in Selection Lists

Use the arrow keys ( and ) to navigate among the individual elements in an active frame containing a selection list. If individual entries within a frame exceed its width, use Shift- or Shift- to scroll horizontally to the right and left. Alternatively, use Ctrl-E or Ctrl-A. This combination can also be used if using or results in changing the active frame or the current selection list, as in the Control Center.

Buttons, Radio Buttons, and Check Boxes

To select buttons with empty square brackets (check boxes) or empty parentheses (radio buttons), press Space or Enter. Alternatively, radio buttons and check boxes can be selected directly with Alt-highlighted_letter. In this case, you do not need to confirm with Enter. If you navigate to an item with Tab, press Enter to execute the selected action or activate the respective menu item.

Function Keys

The F keys (F1 through F12) enable quick access to the various buttons. Available F key shortcuts are shown in the bottom line of the YaST screen. Which function keys are actually mapped to which buttons depend on the active YaST module, because the different modules offer different buttons (Details, Info, Add, Delete, etc.). Use F10 for Accept, OK, Next, and Finish. Press F1 to access the YaST help.

Using Navigation Tree in ncurses Mode

Some YaST modules use a navigation tree in the left part of the window to select configuration dialogs. Use the arrow keys ( and ) to navigate in the tree. Use Space to open or close tree items. In ncurses mode, Enter must be pressed after a selection in the navigation tree in order to show the selected dialog. This is an intentional behavior to save time consuming redraws when browsing through the navigation tree.

Figure 3.2. The Software Installation Module

The Software Installation Module

3.2. Restriction of Key Combinations

If your window manager uses global Alt combinations, the Alt combinations in YaST might not work. Keys like Alt or Shift can also be occupied by the settings of the terminal.

Replacing Alt with Esc

Alt shortcuts can be executed with Esc instead of Alt. For example, Esc H replaces Alt-H. (First press Esc, then press H.)

Backward and Forward Navigation with Ctrl-F and Ctrl-B

If the Alt and Shift combinations are occupied by the window manager or the terminal, use the combinations Ctrl-F (forward) and Ctrl-B (backward) instead.

Restriction of Function Keys

The F keys are also used for functions. Certain function keys might be occupied by the terminal and may not be available for YaST. However, the Alt key combinations and function keys should always be fully available on a pure text console.

3.3. YaST Command Line Options

Besides the text mode interface, YaST provides a pure command line interface. To get a list of YaST command line options, enter:

yast -h

3.3.1. Starting the Individual Modules

To save time, the individual YaST modules can be started directly. To start a module, enter:

yast <module_name>

View a list of all module names available on your system with yast -l or yast --list. Start the network module, for example, with yast lan.

3.3.2. Installing Packages from the Command Line

If you know a package name and the package is provided by any of your active installation repositories, you can use the command line option -i to install the package:

yast -i <package_name>

or

yast --install <package_name>

package_name can be a single short package name, for example gvim, which is installed with dependency checking, or the full path to an rpm package, which is installed without dependency checking.

If you need a command-line based software management utility with functionality beyond what YaST provides, consider using zypper. This new utility uses the same software management library that is also the foundation for the YaST package manager. The basic usage of Zypper is covered in Section 6.1, “Using Zypper”.

3.3.3. Command Line Parameters of the YaST Modules

To use YaST functionality in scripts, YaST provides command line support for individual modules. Not all modules have command line support. To display the available options of a module, enter:

yast <module_name> help

If a module does not provide command line support, the module is started in text mode and the following message appears:

This YaST module does not support the command line interface.

Chapter 4. Snapshots/Rollback with Snapper

Abstract

Being able to do file system snapshots providing the ability to do rollbacks on Linux is a feature that was often requested in the past. Snapper, in conjunction with the Btrfs file system or thin-provisioned LVM volumes now fills that gap.

Btrfs, a new copy-on-write file system for Linux, supports file system snapshots (a copy of the state of a subvolume at a certain point of time) of subvolumes (one or more separately mountable file systems within each physical partition). Snapper lets you manage these snapshots. Snapper comes with a command line and a YaST interface.

By default Snapper and Btrfs on SUSE Linux Enterprise Server are set up to serve as an undo tool for system changes made with YaST and zypper. Before and after running a YaST module or zypper, a snapshot is created. Snapper lets you compare the two snapshots and provides means to revert the differences between the two snapshots. The tools also provide system backups by creating hourly snapshots of the system subvolumes.

4.1. Requirements

Since Btrfs is the only file system on SUSE Linux Enterprise Server supporting snapshots, it is required on all partitions or subvolumes you want to snapshot.

4.1.1. Snapshots and Disk Space

When a snapshot is created, both the snapshot and the original point to the same blocks in the file system. So, initially a snapshot does not occupy additional disk space. If data in the original file system is modified, changed data blocks are copied while the old data blocks are kept for the snapshot. Therefore, a snapshot occupies the same amount of space as the data modified. So, over time, the amount of space a snapshot allocates, constantly grows. As a consequence, deleting files from a Btrfs file system containing snapshots may not free disk space!

[Note]Snapshot Location

Snapshots always reside on the same partition or subvolume that has been snapshotted. It is not possible to store snapshots on a different partition or subvolume.

As a result, partitions containing snapshots need to be larger than normal partitions. The exact amount strongly depends on the number of snapshots you keep and the amount of data modifications. As a rule of thumb you should consider using twice the size than you normally would.

[Tip]Freeing space / Disk Usage

In order to free space on a Btrfs partition containing snapshots you need to delete unneeded snapshots rather than files. Older snapshots occupy more space than recent ones.

Since the df does not show the correct disk usage on Btrfs file systems, you need to use the command btrfs filesystem df MOUNT_POINT. Displaying the amount of disk space a snapshot allocates is currently not supported by the Btrfs tools.

Doing an upgrade from one service pack to another results in snapshots occupying a lot of disk space on the system subvolumes, because a lot of data gets changed (package updates). Manually deleting these snapshots once they are no longer needed is recommended.

Snapper can also be used to create and manage snapshots on thin-provisioned LVM volumes formatted with ext3 or XFS (see Section 4.6, “Using Snapper on Thin-Provisioned LVM Volumes”).

4.2. Using Snapper to Undo System Changes

Snapper on SUSE Linux Enterprise Server is pre-configured to serve as a tool that lets you undo changes made by zypper and YaST. For this purpose, Snapper is configured to create a pair of snapshots before and after each run of zypper and YaST. Snapper also lets you restore system files that have been accidentally deleted or modified. Hourly backups are created for this purpose.

By default, automatic snapshots as described above are configured for the root partition and its subvolumes. In order to make snapshots available for other partitions such as /home for example, you can create custom configurations.

4.2.1. Undoing YaST and Zypper Changes

If you set up the root partition with Btrfs during the installation, Snapper—pre-configured for doing rollbacks of YaST or Zypper changes—will automatically be installed. Every time you start a YaST module or a Zypper transaction, two snapshots are created: a pre-snapshot capturing the state of the file system before the start of the module and a post-snapshot after the module has been finished.

Using the YaST Snapper module or the snapper command line tool, you can undo the changes made by YaST/zypper by restoring files from the pre-snapshot. Comparing two snapshots the tools also allow you to see which files have been changed. You can also display the differences between two versions of a file (diff).

Since Linux is a multitasking system, processes other than YaST or Zypper may modify data in the time frame between the pre- and the post-snapshot. If this is the case, completely reverting to the pre-snapshot will also undo these changes by other processes. In most cases this would be unwanted—therefore it is strongly recommended to closely review the changes between two snapshots before starting the rollback. If there are changes from other processes you want to keep, select which files to roll back.

[Important]Limitations

Make sure you know about Snapper's limitations before attempting to use its rollback mechanism. See Section 4.4, “Limitations” for details.

[Note]Storage Time of Snapshots

By default, the last 100 YaST and Zypper snapshots are kept. If this number is exceeded, the oldest snapshot(s) will be deleted.

Procedure 4.1. Undoing changes using the YaST Snapper module

  1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2 snapper.

  2. Make sure Current Configuration is set to root. This is always the case unless you have manually added own Snapper configurations.

  3. Choose a pair of pre- and post-snapshots from the list. Both, YaST and Zypper snapshot pairs are of the type Pre & Post. YaST snapshots are labeled as yast module_name in the Description column; Zypper snapshots are labeled zypp (zypper).

  4. Click Show Changes to open the list of files that differ between the two snapshots. The following image shows a list of files that have changed after having added the user tester.

  5. Review the list of files. To display a diff between the pre- and post-version of a file, select it from the list. The following images shows the changes to /etc/passwd after having added the user tester.

  6. To restore a set of files, select the relevant files or directories by ticking the respective check box. Click Restore Selected and confirm the action by clicking Yes.

    To restore a single file, activate its diff view by clicking on its name. Click Restore From First and confirm your choice with Yes.

Procedure 4.2. Undoing changes using the snapper command

  1. Get a list of YaST and Zypper snapshots by running snapper list -t pre-post. YaST snapshots are labeled as yast module_name in the Description column; Zypper snapshots are labeled zypp (zypper).

    ~ # snapper list -t pre-post
         Pre # | Post # | Pre Date                 | Post Date                | Description
         ------+--------+--------------------------+--------------------------+----------------------+
         4     | 5      | Tue Jan 10 14:39:14 2012 | Tue Jan 10 14:39:33 2012 | yast system_settings
         65    | 66     | Thu Jan 12 17:18:10 2012 | Thu Jan 12 17:18:23 2012 | zypp(zypper)
         68    | 69     | Thu Jan 12 17:25:46 2012 | Thu Jan 12 17:27:09 2012 | zypp(zypper)
         73    | 74     | Thu Jan 12 17:32:55 2012 | Thu Jan 12 17:33:13 2012 | yast system_settings
         75    | 76     | Thu Jan 12 17:33:56 2012 | Thu Jan 12 17:34:42 2012 | yast users
         77    | 92     | Thu Jan 12 17:38:36 2012 | Thu Jan 12 23:13:13 2012 | yast snapper
         83    | 84     | Thu Jan 12 22:10:33 2012 | Thu Jan 12 22:10:39 2012 | zypp(zypper)
         85    | 86     | Thu Jan 12 22:16:58 2012 | Thu Jan 12 22:17:09 2012 | zypp(zypper)
         88    | 89     | Thu Jan 12 23:10:42 2012 | Thu Jan 12 23:10:46 2012 | zypp(zypper)
         90    | 91     | Thu Jan 12 23:11:40 2012 | Thu Jan 12 23:11:42 2012 | zypp(zypper)
         108   | 109    | Fri Jan 13 13:01:06 2012 | Fri Jan 13 13:01:10 2012 | zypp(zypper)
         
  2. Get a list of changed files for a snapshot pair with snapper status PRE..POST. Files with content changes are marked with c, files that have been added are marked with + and deleted files are marked with -. The following example shows a snapshot pair for the installation of the package ncftp.

    ~ # snapper status 108..109
         +... /usr/bin/ncftp
         +... /usr/bin/ncftpbatch
         +... /usr/bin/ncftpget
         +... /usr/bin/ncftpls
         [...]
         +... /usr/share/man/man1/ncftpspooler.1.gz
         c... /var/cache/zypp/solv/@System/cookie
         c... /var/cache/zypp/solv/@System/solv
         c... /var/lib/rpm/Basenames
         c... /var/lib/rpm/Dirnames
         c... /var/lib/rpm/Filemd5s
         c... /var/lib/rpm/Group
         c... /var/lib/rpm/Installtid
         c... /var/lib/rpm/Name
         c... /var/lib/rpm/Packages
         c... /var/lib/rpm/Providename
         c... /var/lib/rpm/Provideversion
         c... /var/lib/rpm/Requirename
         c... /var/lib/rpm/Requireversion
         c... /var/lib/rpm/Sha1header
         c... /var/lib/rpm/Sigmd5
         c... /var/lib/zypp/SoftLocks
  3. To display the diff for a certain file, run snapper diff PRE..POST FILENAME. If you do not specify FILENAME, a diff for all files will be displayed.

    ~ # snapper diff 108..109 /var/lib/zypp/SoftLocks
         --- /.snapshots/108/snapshot/var/lib/zypp/SoftLocks	2012-01-12 23:15:22.408009164 +0100
         +++ /.snapshots/109/snapshot/var/lib/zypp/SoftLocks	2012-01-13 13:01:08.724009131 +0100
         @@ -1,4 +1,2 @@
         -# zypp::SoftLocksFile generated Thu Jan 12 23:10:46 2012
         -#
         -ncftp
         -#
         +# zypp::SoftLocksFile generated Fri Jan 13 13:01:08 2012
         +##
  4. To restore one or more files run snapper -v undochange PRE..POST FILENAMES. If you do not specify a FILENAMES, all changed files will be restored.

    ~ # snapper -v undochange 108..109
         create:0 modify:16 delete:21
         undoing change...
         deleting /usr/share/man/man1/ncftpspooler.1.gz
         deleting /usr/share/man/man1/ncftpput.1.gz
         [...]
         deleting /usr/bin/ncftpls
         deleting /usr/bin/ncftpget
         deleting /usr/bin/ncftpbatch
         deleting /usr/bin/ncftp
         modifying /var/cache/zypp/solv/@System/cookie
         modifying /var/cache/zypp/solv/@System/solv
         modifying /var/lib/rpm/Basenames
         modifying /var/lib/rpm/Dirnames
         modifying /var/lib/rpm/Filemd5s
         modifying /var/lib/rpm/Group
         modifying /var/lib/rpm/Installtid
         modifying /var/lib/rpm/Name
         modifying /var/lib/rpm/Packages
         modifying /var/lib/rpm/Providename
         modifying /var/lib/rpm/Provideversion
         modifying /var/lib/rpm/Requirename
         modifying /var/lib/rpm/Requireversion
         modifying /var/lib/rpm/Sha1header
         modifying /var/lib/rpm/Sigmd5
         modifying /var/lib/zypp/SoftLocks
         undoing change done

4.2.2. Using Snapper to Restore Files from Hourly Backups

Apart from the YaST and Zypper snapshots, Snapper creates hourly snapshots of the system partition (/). You can use these backup snapshots to restore files that have accidentally been deleted or modified beyond recovery. By making use of Snapper's diff feature you can also find out which modifications have been made at a certain point of time.

Hourly backup snapshots are of the type Single and are marked with the description timeline. To restore files from these snapshots proceed as described in Procedure 4.1, “Undoing changes using the YaST Snapper module” or Procedure 4.2, “Undoing changes using the snapper command”.

[Note]Storage Time of Snapshots

By default, the first snapshot of the last ten days, months, and years are kept. For details see Example 4.1, “Example time line configuration”.

4.2.3. Creating and Modifying Snapper Configurations

The way Snapper behaves is defined in a config file that is specific for each partition or Btrfs subvolume. These config files reside under /etc/snapper/configs/. The default config installed with Snapper for the / directory is named root. It creates and manages the YaST and Zypper snapshots as well as the hourly backup snapshot for /.

You may create your own configurations for other partitions formatted with Btrfs or existing subvolumes on a Btrfs partition. In the following example we will set up a Snapper configuration for backing up the Web server data residing on a separate, Btrfs-formatted partition mounted at /srv/www.

You can use either snapper itself or the YaST Snapper module to restore files from these snapshots. In YaST you need to select your Current Configuration, while you need to specify your config for snapper with the global switch -c (e.g. snapper -c myconfig list).

To create a new Snapper configuration, run snapper create-config:

snapper -c www-data1 create-config
   /srv/www2

1

Name of config file.

2

Mount point of the partition or Btrfs subvolume to snapshot.

This command will create a new config file /etc/snapper/config-templates/www-data with reasonable default values (taken from /etc/snapper/config-templates/default).

[Tip]Config Defaults

Default values for a new config are taken from /etc/snapper/config-templates/default. To use your own set of defaults, create a copy of this file in the same directory and adjust it to your needs. To use it, specify the -t option with the create-config command:

snapper -c www-data create-config -t my_defaults /srv/www

4.2.3.1. Adjusting the Config File

To adjust the config file, you need to modify it with an editor. It contains key/value pairs in the form of key=value. You may only change the value.

SUBVOLUME

Mount point of the partition or subvolume to snapshot. Do not change.

FSTYPE

File system type of the partition. Do not change.

NUMBER_CLEANUP

Defines whether to automatically delete old snapshots when the total snapshot count exceeds a number specified with NUMBER_LIMIT and an age specified with NUMBER_MIN_AGE. Valid values: yes, no

[Note]Limit and Age

NUMBER_LIMIT and NUMBER_MIN_AGE are always evaluated both. Snapshots are only deleted when both conditions are met. If you always want to keep a certain number of snapshots regardless of their age, set NUMBER_MIN_AGE to 0. On the other hand, if you do not want to keep snapshots beyond a certain age, set NUMBER_LIMIT to 0.

NUMBER_LIMIT

Defines how many snapshots to keep if NUMBER_CLEANUP is set to yes.

NUMBER_MIN_AGE

Defines the minimum age in seconds a snapshot must have before it can automatically be deleted.

TIMELINE_CREATE

If set to yes, hourly snapshots are created.This is currently the only way to automatically create snapshots, therefore setting it to yes is strongly recommended. Valid values: yes, no

TIMELINE_CLEANUP

Defines whether to automatically delete old snapshots when the snapshot count exceeds a number specified with the TIMELINE_LIMIT_* options and an age specified with TIMELINE_MIN_AGE. Valid values: yes, no

TIMELINE_MIN_AGE

Defines the minimum age in seconds a snapshot must have before it can automatically be deleted.

TIMELINE_LIMIT_HOURLY, TIMELINE_LIMIT_DAILY, TIMELINE_LIMIT_MONTHLY, TIMELINE_LIMIT_YEARLY

Number of snapshots to keep for hour, day, month, year.

Example 4.1. Example time line configuration

TIMELINE_CREATE="yes"
        TIMELINE_CLEANUP="yes"
        TIMELINE_MIN_AGE="1800"
        TIMELINE_LIMIT_HOURLY="10"
        TIMELINE_LIMIT_DAILY="10"
        TIMELINE_LIMIT_MONTHLY="10"
        TIMELINE_LIMIT_YEARLY="10"
        

This example configuration enables hourly snapshots which are automatically cleaned up. TIMELINE_MIN_AGE and TIMELINE_LIMIT_* are always evaluated both. In this example, the minimum age of a snapshot, before it can be deleted is set to 30 minutes (1800 seconds). Since we create hourly snapshots, this ensures that only the latest snapshots are kept. If TIMELINE_LIMIT_DAILY is set to not zero, this means that the first snapshot of the day is kept, too.

Snapshots to be Kept

  • Hourly: The last ten snapshots that have been made.

  • Daily: The first daily snapshot that has been made is kept for the last ten days.

  • Monthly: The first snapshot made on the last day of the month is kept for the last ten months.

  • Yearly: The first snapshot made on the last day of the year is kept for the last ten years.

4.2.3.2. Using Snapper as Regular User

By default Snapper can only be used by root. However, there are cases in which certain groups or users need to be able to create snapshots or undo changes by reverting to a snapshot:

  • a website administrator wants to snapshot /srv/www.

  • a database administrator wants to snapshot the databases.

  • a user wants to snapshot her home directory.

For these purposes Snapper configurations that grant permissions to users or/and groups can be created. In addition to this configuration change, the corresponding .snapshots directory needs to be readable and accessible by the specified users.

Procedure 4.3. Enabling Regular Users to Use Snapper

Note that all steps in this procedure need to be run by root.

  1. If not existing, create a Snapper configuration for the partition or subvolume on which the user should be able to use Snapper. Refer to Section 4.2.3, “Creating and Modifying Snapper Configurations” for instructions. Example:

    snapper --config web_data create /srv/www
  2. The configuration file is created under /etc/snapper/configs/NAME, where NAME is the value you specified with -c/--config in the previous step (for example /etc/snapper/configs/web_data). Adjust it according to your needs; see Section 4.2.3.1, “Adjusting the Config File” for details.

  3. Set values for ALLOW_USERS and/or ALLOW_GROUPS to grant permissions to users and/or groups, respectively. Multiple entries need to be separated by Space. To grant permissions to the user www_admin for example, enter:

    ALLOW_USERS="www_admin"
  4. Grant read and access permissions on the snapshot directory PATH/.snapshots. PATH is to be replaced by the subvolume you specified in the first step of this procedure. Example:

    chmod a+rx /srv/www/.snapshots

    The given Snapper configuration can now be used by the specified user(s) and/or group(s). You can test it with the list command, for example:

    www_admin:~ > snapper -c web_data list

4.2.4. Disabling Automatic Snapshots

If you have set up the root partition with Btrfs during the installation, Snapper automatically creates hourly snapshots of the system, as well as pre- and post-snapshots for YaST and zypper transactions. Each of these tasks can be disabled as follows:

Disabling hourly snapshots

Edit /etc/snapper/configs/root and set TIMELINE_CREATE to no:

TIMELINE_CREATE="no"
Disabling Zypper snapshots

Uninstall the package snapper-zypp-plugin

Disabling YaST snapshots

Edit /etc/sysconfig/yast2 and set USE_SNAPPER to no:

USE_SNAPPER="no"

4.3. Manually Creating and Managing Snapshots

Snapper is not restricted to creating and managing snapshots automatically by configuration; you can also create snapshot pairs (before and after) or single snapshots manually using either the command line tool or the YaST module.

All Snapper operations are carried out for an existing configuration (see Section 4.2.3, “Creating and Modifying Snapper Configurations” for details). You can only snapshot partitions or volumes for which a configuration exists. By default the system configuration (root) is used. If you want to create or manage snapshots for your own configuration you need to explicitly choose it. Use the Current Configuration drop-down menu in YaST or specify the -c on the command line (snapper -c MYCONFIG COMMAND).

4.3.1. Snapshot Metadata

Each snapshot consists of the snapshot itself and some metadata. When creating a snapshot you also need to specify the metadata. Modifying a snapshot means changing its metadata—you cannot modify its content. The following metadata is available for each snapshot:

  • Type: Snapshot type, see Section 4.3.1.1, “Snapshot Types” for details. This data cannot be changed.

  • Number: Unique number of the snapshot. This data cannot be changed.

  • Pre Number: Specifies the number of the corresponding pre snapshot. For snapshots of type post only. This data cannot be changed.

  • Description: A description of the snapshot.

  • Userdata: An extended description where you can specify custom data in the form of a comma-separated key=value list: reason=testing_stuff, user=tux

  • Cleanup-Algorithm: Cleanup-algorithm for the snapshot, see Section 4.3.1.2, “Cleanup-algorithms” for details.

4.3.1.1. Snapshot Types

Snapper knows three different types of snapshots: pre, post, and single. Physically they do not differ, but Snapper handles them differently.

pre

Snapshot of a file system before a modification. Each pre snapshot has got a corresponding post snapshot. Used e.g. for the automatic YaST/zypper snapshots.

post

Snapshot of a file system after a modification. Each post snapshot has got a corresponding pre snapshot. Used e.g. for the automatic YaST/zypper snapshots.

single

Stand-alone snapshot. Used e.g. for the automatic hourly snapshots. This is the default type when creating snapshots.

4.3.1.2. Cleanup-algorithms

Snapper provides three algorithms to clean up old snapshots. The algorithms are executed in a daily cron-job. The cleanup-frequency itself is defined in the Snapper configuration for the partition or subvolume (see Section 4.2.3.1, “Adjusting the Config File” for details).

number

Deletes old snapshots when a certain snapshot count is reached.

time line

Deletes old snapshots having passed a certain age, but keeps a number of hourly, daily, monthly, and yearly snapshots.

empty-pre-post

Deletes pre/post snapshot pairs with empty diffs.

4.3.2. Creating Snapshots

Creating a snapshot is done by running snapper create or by clicking Create in the YaST module Snapper. The following examples explain how to create snapshots from the command line. It should be easy to adopt them when using the YaST interface.

[Tip]Snapshot Description

You should always specify a meaningful description in order to later be able to identify its purpose. Even more information can be specified via the user data option.

snapper create --description "Snapshot for week 2 2013"

Creates a stand-alone snapshot (type single) for the default (root) configuration with a description. Because no cleanup-algorithm is specified, the snapshot will never be deleted automatically.

snapper --config home create --description "Cleanup in ~tux"

Creates a stand-alone snapshot (type single) for a custom configuration named home with a description. Because no cleanup-algorithm is specified, the snapshot will never be deleted automatically.

snapper --config home create --description "Daily data backup" --cleanup-algorithm timeline

Creates a stand-alone snapshot (type single) for a custom configuration named home with a description. The file will automatically be deleted when it meets the criteria specified for the time line cleanup-algorithm in the configuration.

snapper create --type pre--print-number--description "Before the Apache config cleanup"

Creates a snapshot of the type pre and prints the snapshot number. First command needed to create a pair of snapshots used to save a before and after state.

snapper create --type post--pre-number 30--description "After the Apache config cleanup"

Creates a snapshot of the type post paired with the pre snapshot number 30. Second command needed to create a pair of snapshots used to save a before and after state.

snapper create --command COMMAND--description "Before and after COMMAND"

Automatically creates a snapshot pair before and after running COMMAND. This option is only available when using snapper on the command line.

4.3.3. Modifying Snapshot Metadata

Snapper allows you to modify the description, the cleanup algorithm, and the userdata of a snapshot. All other metadata cannot be changed. The following examples explain how to modify snapshots from the command line. It should be easy to adopt them when using the YaST interface.

To modify a snapshot on the command line, you need to know its number. Use snapper list to display all snapshots and their numbers.

The YaST Snapper module already lists all snapshots. Choose one from the list and click Modify.

snapper modify --cleanup-algorithm "timeline" 10

Modifies the metadata of snapshot 10 for the default (root) configuration. The cleanup algorithm is set to timeline.

snapper --config home modify --description "daily backup" -cleanup-algorithm "timeline"120

Modifies the metadata of snapshot 120 for a custom configuration named home. A new description is set and the cleanup algorithm is unset.

4.3.4. Deleting Snapshots

To delete a snapshot with the YaST Snapper module, choose a snapshot from the list and click Delete.

To delete a snapshot with the command line tool, you need to know its number. Get it by running snapper list. To delete a snapshot, run snapper delete NUMBER.

[Tip]Deleting Snapshot Pairs

When deleting a pre snapshot, you should always delete its corresponding post snapshot (and vice versa).

snapper delete 65

Deletes snapshot 65 for the default (root) configuration.

snapper -c home delete 89 90

Deletes snapshots 89 and 90 for a custom configuration named home.

[Tip]Old Snapshots Occupy More Disk Space

If you delete snapshots in order to free space on your hard disk (see Section 4.1.1, “Snapshots and Disk Space” for details), make sure to delete old snapshots first. The older a snapshot is, the more disk space it occupies.

Snapshots are also automatically deleted by a daily cron-job. Refer to Section 4.3.1.2, “Cleanup-algorithms” for details.

4.4. Limitations

Although being ready for production, Btrfs as well as Snapper are constantly developed further. The following limitations exist at the moment. It is planned to solve these issues in future releases.

4.4.1. Data Consistency

There is no mechanism to ensure data consistency when creating snapshot. Whenever a file is written (e.g. a database) at the same time the snapshot is created, it will result in a broken or partly written file. Restoring such a file will cause problems. Therefore it is strongly recommended to always closely review the list of changed files and their diffs. Only restore files that really need to belonging to the action you want to roll back.

4.4.2. Reverting User Additions

Usually /home resides on a separate partition. Such a separate partition is not part of the default configuration for doing YaST rollbacks. Therefore the user's home partition will not be deleted when reverting a user addition using Snapper. It is strongly recommended to use the YaST User and Group Management tool to remove users.

4.4.3. No Rollback on /boot and Boot Loader Changes

Currently SUSE Linux Enterprise Server cannot boot from Btrfs partitions. Therefore a separate partition for /boot is created upon the installation when using Btrfs for the system partition. Since /boot does not support snapshots, the following restrictions apply for YaST/zypper rollbacks:

no rollback for any configuration changes on the boot loader

The only file that can be rolled back is the boot loader configuration file in /etc. The main configuration files reside under /boot and cannot be rolled back.

no complete rollback for Kernel installations

The Kernel itself and its initrd are installed in the /boot partition, whereas Kernel modules or sources are installed in /var/lib and /usr/src, respectively. Furthermore, each Kernel installation also changes the boot loader configuration files in /boot. So whenever you do a rollback that involves undoing a Kernel installation, you need to manually remove the Kernel and its initrd from /boot and adjust the boot loader configuration by removing the boot entry for the Kernel.

4.5. Frequently Asked Questions

Why does Snapper Never Show Changes in /var/log, /tmp and Other Directories?

For some directories we decided to disable snapshotting, e.g. /var/log since reverting logs makes searching for problems difficult. To exclude a path from snapshotting we create a subvolume for that path. The following mount points are excluded from snapshotting on SUSE Linux Enterprise Server:

  • /opt

  • /srv

  • /tmp

  • /var/crash

  • /var/log

  • /var/run

  • /var/spool

  • /var/tmp

Can I Boot a Snapshot from the Boot Loader?

This is currently not possible. The boot loader on SUSE Linux Enterprise Server currently does not support booting from a Btrfs partition.

4.6. Using Snapper on Thin-Provisioned LVM Volumes

Apart from snapshots on Btrfs file systems, snapper also supports snapshotting on thin-provisioned LVM volumes (snapshots on regular LVM volumes are not supported) formatted with ext3 or XFS. For more information and setup instructions, refer to Section “LVM Configuration” (Chapter 15, Advanced Disk Setup, ↑Deployment Guide).

In order to use Snapper on a thin-provisioned LVM volume you need to create a Snapper configuration for it. On LVM it is required to specify the file system with --fstype=lvm(FILESYSTEM). To date ext3 and XFS are supported, so ext3 or xfs are valid values for FILESYSTEM. Example:

snapper -c lvm create-config --fstype="lvm(xfs)" /thin_lvm

You can adjust this configuration according to your needs as described in Section 4.2.3.1, “Adjusting the Config File”. Now you can use Snapper to create and manage snapshots, to restore files, and undo changes as described above.

Chapter 5. Remote Access with VNC

Abstract

Virtual Network Computing (VNC) enables you to control a remote computer via a graphical desktop (as opposed to a remote shell access). VNC is platform-independent and lets you access the remote machine from any operating system.

SUSE Linux Enterprise Server supports two different kinds of VNC sessions: One-time sessions that live as long as the VNC connection from the client is kept up, and persistent sessions that live until they are explicitly terminated.

[Note]Session Types

A machine can offer both kinds of sessions simultaneously on different ports, but an open session cannot be converted from one type to the other.

5.1. One-time VNC Sessions

A one-time session is initiated by the remote client. It starts a graphical login screen on the server. This way you can choose the user which starts the session and, if supported by the login manager, the desktop environment. Once you terminate the client connection to such a VNC session, all applications started within that session will be terminated, too. One-time VNC sessions cannot be shared, but it is possible to have multiple sessions on a single host at the same time.

Procedure 5.1. Enabling One-time VNC Sessions

  1. Start YaST+Network Services+Remote Administration (VNC).

  2. Check Allow Remote Administration.

  3. If necessary, also check Open Port in Firewall (for example, when your network interface is configured to be in the External Zone). If you have more than one network interface, restrict opening the firewall ports to a specific interface via Firewall Details.

  4. Confirm your settings with Finish.

  5. In case not all needed packages are available yet, you need to approve the installation of missing packages.

[Note]Available Configurations

The default configuration on SUSE Linux Enterprise Server serves sessions with a resolution of 1024x768 pixels at a color depth of 16-bit. The sessions are available on ports 5901 for regular VNC viewers (equivalent to VNC display 1) and on port 5801 for Web browsers.

Other configurations can be made available on different ports, see Section 5.1.2, “Configuring One-time VNC Sessions”.

VNC display numbers and X display numbers are independent in one-time sessions. A VNC display number is manually assigned to every configuration that the server supports (:1 in the example above). Whenever a VNC session is initiated with one of the configurations, it automatically gets a free X display number.

5.1.1. Initiating a One-time VNC Session

To initiate a one-time VNC session, a VNC viewer must be installed on the client machine. The standard viewer on SUSE Linux products is vncviewer, provided by the package tightvnc. You may also view a VNC session using your Web browser and a Java applet.

To start your VNC viewer and initiate a session with the server's default configuration, use the command:

vncviewer jupiter.example.com:1

Instead of the VNC display number you can also specify the port number with two colons:

vncviewer jupiter.example.com::5901

Alternatively use a Java-capable Web browser to view the VNC session by entering the following URL: http://jupiter.example.com:5801

5.1.2. Configuring One-time VNC Sessions

You can skip this section, if you do not need or want to modify the default configuration.

One-time VNC sessions are started via the xinetd daemon. A configuration file is located at /etc/xinetd.d/vnc. By default it offers six configuration blocks: three for VNC viewers (vnc1 to vnc3), and three serving a Java applet (vnchttpd1 to vnchttpd3). By default only vnc1 and vnchttpd1 are active.

To activate a configuration, comment the line disable = yes with a # character in the first column, or remove that line completely. To deactivate a configuration uncomment or add that line.

The Xvnc server can be configured via the server_args option—see Xnvc --help for a list of options.

When adding custom configurations, make sure they are not using ports that are already in use by other configurations, other services, or existing persistent VNC sessions on the same host.

Activate configuration changes by entering the following command:

rcxinetd reload
[Important]Firewall and VNC Ports

When activating Remote Administration as described in Procedure 5.1, “Enabling One-time VNC Sessions”, the ports 5801 and 5901 are opened in the firewall. If the network interface serving the VNC sessions is protected by a firewall, you need to manually open the respective ports when activating additional ports for VNC sessions. See Chapter 15, Masquerading and Firewalls (↑Security Guide) for instructions.

5.2. Persistent VNC Sessions

A persistent VNC session is initiated on the server. The session and all applications started in this session run regardless of client connections until the session is terminated.

A persistent session can be accessed from multiple clients simultaneously. This is ideal for demonstration purposes where one client has full access and all other clients have view-only access. Another usecase are trainings where the trainer might need access to the trainee's desktop. However, most of the times you probably do not want to share your VNC session.

In contrast to one-time sessions that start a display manager, a persistent session starts a ready-to operate desktop that runs as the user that started the VNC session.

Access to persistent sessions is protected by two possible types of passwords:

  • a regular password that grants full access or

  • an optional view-only password that grants a non-interactive (view-only) access.

A session can have multiple client connections of both kinds at once.

Procedure 5.2. Starting a Persistent VNC Session

  1. Open a shell and make sure you are logged in as the user that should own the VNC session.

  2. If the network interface serving the VNC sessions is protected by a firewall, you need to manually open the port used by your session in the firewall. If starting multiple sessions you may alternatively open a range of ports. See Chapter 15, Masquerading and Firewalls (↑Security Guide) for details on how to configure the firewall.

    vncserver uses the ports 5901 for display :1, 5902 for display :2, and so on. For persistent sessions, the VNC display and the X display usually have the same number.

  3. To start a session with a resolution of 1024x769 pixel and with a color depth of 16-bit, enter the following command:

    vncserver -geometry 1024x768 -depth 16

    The vncserver command picks an unused display number when none is given and prints out its choice. See man 1 vncserver for more options.

When running vncviewer for the first time, it asks for a password for full access to the session. If needed, you can also provide a password for view-only access to the session.

The password(s) you are providing here are also used for future sessions started by the same user. They can be changed with the vncpasswd command.

[Important]Security Considerations

Make sure to use strong passwords of significant length (eight or more characters). Do not share these passwords.

VNC connections are unencrypted, so people who can sniff the network(s) between the two machines can read the password when it gets transferred at the beginning of a session.

To terminate the session shut down the desktop environment that runs inside the VNC session from the VNC viewer as you would shut it down if it was a regular local X session.

If you prefer to manually terminate a session, open a shell on the VNC server and make sure you are logged in as the user that owns the VNC session you want to terminate. Run the following command to terminate the session that runs on display :1: vncserver -kill :1

5.2.1. Connecting to a Persistent VNC Session

To connect to a persistent VNC session, a VNC viewer must be installed. The standard viewer on SUSE Linux products is vncviewer, provided by the package tightvnc. You may also view a VNC session using your Web browser and a Java applet.

To start your VNC viewer and connect to display :1 of the VNC server, use the command

vncviewer jupiter.example.com:1

Instead of the VNC display number you can also specify the port number with two colons:

vncviewer jupiter.example.com::5901

Alternatively use a Java-capable Web browser to view the VNC session by entering the following URL: http://jupiter.example.com:5801

5.2.2. Configuring Persistent VNC Sessions

Persistent VNC sessions can be configured by editing $HOME/.vnc/xstartup. By default this shell script starts an xterm and the twm Window Manager. To start either GNOME or KDE instead, replace the line starting twm with one of the following:

/usr/bin/gnome     # GNOME
/usr/bin/startkde  # KDE
[Note]One Configuration for Each User

Persistent VNC sessions are configured in a single per-user configuration. Multiple sessions started by a user will all use the same start-up and password files.

Chapter 6. Managing Software with Command Line Tools

Abstract

This chapter describes Zypper and RPM, two command line tools for managing software. For a definition of the terminology used in this context (for example, repository, patch, or update) refer to Section “Definition of Terms” (Chapter 9, Installing or Removing Software, ↑Deployment Guide).

6.1. Using Zypper

Zypper is a command line package manager for installing, updating and removing packages as well as for managing repositories. Zypper's syntax is similar to that of rug. In contrast to rug, Zypper does not require the zmd daemon to run behind the scenes. For more information about rug compatibility, see man zypper, section COMPATIBILITY WITH RUG. It is especially useful for accomplishing remote software management tasks or managing software from shell scripts.

6.1.1. General Usage

The general syntax of Zypper is:

zypper [global-options]command[command-options][arguments] ...

The components enclosed in brackets are not required. The simplest way to execute Zypper is to type its name, followed by a command. For example, to apply all needed patches to the system type:

zypper patch

Additionally, you can choose from one or more global options by typing them just before the command. For example, --non-interactive means running the command without asking anything (automatically applying the default answers):

zypper --non-interactive patch

To use the options specific to a particular command, type them right after the command. For example, --auto-agree-with-licenses means applying all needed patches to the system without asking to confirm any licenses (they will automatically be accepted):

zypper patch --auto-agree-with-licenses

Some commands require one or more arguments. When using the install command, for example, you need to specify which package(s) to install:

zypper install mplayer

Some options also require an argument. The following command will list all known patterns:

zypper search -t pattern

You can combine all of the above. For example, the following command will install the mplayer and amarok packages from the factory repository while being verbose:

zypper -v install --from factory mplayer amarok

The --from option makes sure to keep all repositories enabled (for solving any dependencies) while requesting the package from the specified repository.

Most Zypper commands have a dry-run option that does a simulation of the given command. It can be used for test purposes.

zypper remove --dry-run MozillaFirefox

Zypper supports the global --userdata string option for transaction identification purposes. The user-defined string is passed to Zypper history logs in /var/log/zypp/history and Snapper.

zypper --userdata string patch

6.1.2. Installing and Removing Software with Zypper

To install or remove packages use the following commands:

zypper install package_name
zypper remove package_name

Zypper knows various ways to address packages for the install and remove commands:

by the exact package name (and version number)
zypper install MozillaFirefox

or

zypper install MozillaFirefox-3.5.3
by repository alias and package name
zypper install mozilla:MozillaFirefox

Where mozilla is the alias of the repository from which to install.

by package name using wild cards

The following command will install all packages that have names starting with Moz. Use with care, especially when removing packages.

zypper install 'Moz*'
by capability

For example, if you would like to install a perl module without knowing the name of the package, capabilities come in handy:

zypper install 'perl(Time::ParseDate)'
by capability and/or architecture and/or version

Together with a capability you can specify an architecture (such as i586 or x86_64) and/or a version. The version must be preceded by an operator: < (lesser than), <= (lesser than or equal), = (equal), >= (greater than or equal), > (greater than).

zypper install 'firefox.x86_64'
zypper install 'firefox>=3.5.3'
zypper install 'firefox.x86_64>=3.5.3'
by path to the RPM file

You can also specify a local or remote path to a package:

zypper install /tmp/install/MozillaFirefox.rpm
zypper install http://download.opensuse.org/repositories/mozilla/SUSE_Factory/x86_64/MozillaFirefox-3.5.3-1.3.x86_64.rpm

To install and remove packages simultaneously use the +/- modifiers. To install emacs and remove vim simultaneously, use:

zypper install emacs -vim

To remove emacs and install vim simultaneously, use:

zypper remove emacs +vim

To prevent the package name starting with the - being interpreted as a command option, always use it as the second argument. If this is not possible, precede it with --:

zypper install -emacs +vim       # Wrong
zypper install vim -emacs        # Correct
zypper install -- -emacs +vim    # same as above
zypper remove emacs +vim         # same as above

If (together with a certain package) you automatically want to remove any packages that become unneeded after removing the specified package, use the --clean-deps option:

rm package_name --clean-deps

By default, Zypper asks for a confirmation before installing or removing a selected package, or when a problem occurs. You can override this behavior using the --non-interactive option. This option must be given before the actual command (install, remove, and patch) as in the following:

zypper --non-interactive install package_name

This option allows the use of Zypper in scripts and cron jobs.

[Warning]Do not Remove Mandatory System Packages

Do not remove packages such as glibc, zypper, kernel, or similar packages. These packages are mandatory for the system and, if removed, may cause the system to become unstable or stop working altogether.

6.1.2.1. Installing or Downloading Source Packages

If you want to install the corresponding source package of a package, use:

zypper source-install package_name

That command will also install the build dependencies of the specified package. If you do not want this, add the switch -D. To install only the build dependencies use -d.

zypper source-install -D package_name # source package only
zypper source-install -d package_name # build dependencies only

Of course, this will only work if you have the repository with the source packages enabled in your repository list (it is added by default, but not enabled). See Section 6.1.5, “Managing Repositories with Zypper” for details on repository management.

A list of all source packages available in your repositories can be obtained with:

zypper search -t srcpackage

You can also download source packages for all installed packages to a local directory. To download source packages, use:

zypper source-download

The default download directory is /var/cache/zypper/source-download. You can change it using the --directory option. To only show missing or extraneous packages without downloading or deleting anything, use the --status option. To delete extraneous source packages, use the --delete option. To disable deleting, use the --no-delete option.

6.1.2.2. Utilities

To verify whether all dependencies are still fulfilled and to repair missing dependencies, use:

zypper verify

In addition to dependencies that must be fulfilled, some packages recommend other packages. These recommended packages are only installed if actually available and installable. In case recommended packages were made available after the recommending package has been installed (by adding additional packages or hardware), use the following command:

zypper install-new-recommends

This command is very useful after plugging in a webcam or WLAN device. It will install drivers for the device and related software, if available. Drivers and related software are only installable if certain hardware dependencies are fulfilled.

6.1.3. Updating Software with Zypper

There are three different ways to update software using Zypper: by installing patches, by installing a new version of a package or by updating the entire distribution. The latter is achieved with the zypper dist-upgrade command which is discussed in Section 6.1.4, “Distribution Upgrade with zypper”.

6.1.3.1. Installing Patches

To install all officially released patches applying to your system, just run:

zypper patch

In this case, all patches available in your repositories are checked for relevance and installed, if necessary. After registering your SUSE Linux Enterprise Server installation, an official update repository containing such patches will be added to your system. The above command is all you must enter in order to apply them when needed.

Zypper knows three different commands to query for the availability of patches:

zypper patch-check

Lists the number of needed patches (patches, that apply to your system but are not yet installed)

~ # zypper patch-check
Loading repository data...
Reading installed packages...
5 patches needed (1 security patch)
zypper list-patches

Lists all needed patches (patches, that apply to your system but are not yet installed)

~ # zypper list-patches
Loading repository data...
Reading installed packages...
 
Repository                          | Name      | Version | Category | Status
------------------------------------+-----------+---------+----------+-------
Updates for openSUSE 11.3 11.3-1.82 | lxsession | 2776    | security | needed
zypper patches

Lists all patches available for SUSE Linux Enterprise Server, regardless of whether they are already installed or apply to your installation.

It is also possible to list and install patches relevant to specific issues. To list specific patches, use the zypper list-patches command with the following options:

--bugzilla[=number]

Lists all needed patches for Bugzilla issues. Optionally, you can specify a bug number if you only want to list patches for this specific bug.

--cve[=number]

Lists all needed patches for CVE (Common Vulnerabilities and Exposures) issues, or only patches matching a certain CVE number, if specified.

To install a patch for a specific Bugzilla or CVE issue, use the following commands:

zypper patch --bugzilla=number

or

zypper patch --cve=number

For example, to install a security patch with the CVE number CVE-2010-2713, execute:

zypper patch --cve=CVE-2010-2713

6.1.3.2. Installing Updates

If a repository contains only new packages, but does not provide patches, zypper patch does not show any effect. To update all installed packages with newer available versions, use:

zypper update

To update individual packages, specify the package with either the update or install command:

zypper update package_name
zypper install package_name

A list of all new installable packages can be obtained with the command:

zypper list-updates

Note that this command only packages lists packages that match the following criteria:

  • has the same vendor like the already installed package,

  • is provided by repositories with at least the same priority than the already installed package,

  • is installable (all dependencies are satisfied).

A list of all new available packages (regardless whether installable or not) can be obtained with:

zypper list-updates --all

To find out why a new package cannot be installed, just use the zypper install or zypper update command as described above.

6.1.3.3. Upgrading to a New Product Version

To easily upgrade your installation to a new product version (for example, from SUSE Linux Enterprise Server 11 to SUSE Linux Enterprise Server 11 SP1, first adjust your repositories to match the current SUSE Linux Enterprise Server repositories. For details, refer to Section 6.1.5, “Managing Repositories with Zypper”. Then use the zypper dist-upgrade command with the required repositories. This command ensures that all packages will be installed from the repositories currently enabled. For detailed instructions, refer to Section 6.1.4, “Distribution Upgrade with zypper”.

To restrict the distribution upgrade to packages from a certain repository while considering also the other repositories for satisfying dependencies, use the --from option and specify the repository by either its alias, its number or URI.

[Note]Differences between zypper update and zypper dist-upgrade

Choose zypper update to update packages to newer versions available for your product version while maintaining system integrity. zypper update will honor the following rules:

no vendor changes
no architecture changes
no downgrades
keep installed packages

When executing zypper dist-upgrade, all packages will be installed from the repositories currently enabled. This rule is enforced, so packages might change vendor or architecture or even might get downgraded. All packages that have unfulfilled dependencies after the upgrade will be uninstalled.

6.1.4. Distribution Upgrade with zypper

With the zypper command line utility you can upgrade to the next version of the distribution. Most importantly, you can initiate the system upgrade process from within the running system.

This feature is attractive for advanced users who want to run remote upgrades or upgrades on many similarly configured systems.

6.1.4.1. Before Starting the Upgrade with zypper

To avoid unexpected errors during the upgrade process using zypper, minimize risky constellations:

  • Close as many applications and unneeded services as possible and log out all regular users.

  • Disable third party repositories before starting the upgrade, or lower the priority of these repositories to make sure packages from the default system repositories will get preference. Enable them again after the upgrade and edit their version string to match the version number of the distribution of the upgraded now running system.

6.1.4.2. The Upgrade Procedure

[Warning]Check Your System Backup

Before actually starting the upgrade procedure, check that your system backup is up-to-date and restorable. This is especially important because you must enter many of the following steps manually.

The program zypper supports long and short command names. For example, you can abbreviate zypper install as zypper in. In the following text, the short variants are used.

  1. Run the online update to make sure the software management stack is up-to-date. For more information, see Chapter 1, YaST Online Update.

  2. Configure the repositories you want to use as an update source. Getting this right is essential. Either use YaST (see Section “Managing Software Repositories and Services” (Chapter 9, Installing or Removing Software, ↑Deployment Guide)) or zypper (see Section 6.1, “Using Zypper”). The name of the repositories as used in the following steps could vary a little bit depending on your customizations.

    Consider to prepare or update your own installation server. For background information, see Section “Setting Up an Installation Server Using YaST” (Chapter 14, Remote Installation, ↑Deployment Guide).

    To view your current repositories enter:

    zypper lr -u
    1. Increase the version number of the system repositories from 11-SP2 to 11-SP3; add the new repositories with commands such as:

      server=http://download.example.org
      zypper ar $server/distribution/11-SP3/repo/oss/ SLE-11-SP3
      zypper ar $server/update/11-SP3/ SLE-11-SP3-Update

      And remove the old repositories:

      zypper rr SLE-11-SP2
      zypper rr SLE-11-Update
    2. Disable third party repositories or other Open Build Service repositories, because zypper dup is guaranteed to work with the default repositories only (replace repo-alias with the name of the repository you want to disable):

      zypper mr -d repo-alias

      Alternatively, you can lower the priority of these repositories.

      [Note]Handling of Unresolved Dependencies

      zypper dup will remove all packages having unresolved dependencies, but it keeps packages of disabled repositories as long as their dependencies are satisfied.

      zypper dup ensures that all installed packages come from one of the available repositories. It does not consider the version, architecture, or vendor of the installed packages; thus it emulates a fresh installation. Packages that are no longer available in the repositories are considered orphaned. Such packages get uninstalled if their dependencies cannot be satisfied. If they can be satisfied, such packages stay installed.

    3. Once done, check your repository configuration with:

      zypper lr -d
  3. Refresh local metadata and repository contents with zypper ref.

  4. Pull in Zypper and the package management stack from the 11 SP1 repository with zypper up zypper.

  5. Run the actual distribution upgrade with zypper dup. You are asked to confirm the license of SUSE Linux Enterprise and of some packages—depending on the set of installed packages.

  6. Perform basic system configuration with SuSEconfig.

  7. Reboot the system with shutdown -r now.

6.1.5. Managing Repositories with Zypper

All installation or patch commands of Zypper rely on a list of known repositories. To list all repositories known to the system, use the command:

zypper repos

The result will look similar to the following output:

Example 6.1. Zypper—List of Known Repositories


# | Alias                             | Name                              | Enabled | Refresh
--+-----------------------------------+-----------------------------------+---------+--------
1 | SUSE-Linux-Enterprise-Server 11-0 | SUSE-Linux-Enterprise-Server 11-0 | Yes     | No
2 | SLES-11-Updates                   | SLES 11 Online Updates            | Yes     | Yes
3 | broadcomdrv                       | Broadcom Drivers                  | Yes     | No      

When specifying repositories in various commands, an alias, URI or repository number from the zypper repos command output can be used. A repository alias is a short version of the repository name for use in repository handling commands. Note that the repository numbers can change after modifying the list of repositories. The alias will never change by itself.

By default, details such as the URI or the priority of the repository are not displayed. Use the following command to list all details:

zypper repos -d

6.1.5.1. Adding Repositories

To add a repository, run

zypper addrepo URIalias

URI can either be an Internet repository, a network resource, a directory or a CD or DVD (see http://en.opensuse.org/openSUSE:Libzypp_URIs for details). The alias is a shorthand and unique identifier of the repository. You can freely choose it, with the only exception that is has to be unique. Zypper will issue a warning if you specify an alias that is already in use.

6.1.5.2. Removing Repositories

If you want to remove a repository from the list, use the command zypper removerepo together with the alias or number of the repository you want to delete. For example, to remove the repository listed as third entry in Example 6.1, “Zypper—List of Known Repositories”, use the following command:

zypper removerepo 3

6.1.5.3. Modifying Repositories

Enable or disable repositories with zypper modifyrepo. You can also alter the repository's properties (such as refreshing behavior, name or priority) with this command. The following command will enable the repository named updates, turn on auto-refresh and set its priority to 20:

zypper modifyrepo -er -p 20 'updates'

Modifying repositories is not limited to a single repository—you can also operate on groups:

-a: all repositories
-l: local repositories
-t: remote repositories
-m TYPE: repositories of a certain type (where TYPE can be one of the following: http, https, ftp, cd, dvd, dir, file, cifs, smb, nfs, hd, iso)

To rename a repository alias, use the renamerepo command. The following example changes the alias from Mozilla Firefox to just firefox:

zypper renamerepo 'Mozilla Firefox' firefox

6.1.6. Querying Repositories and Packages with Zypper

Zypper offers various methods to query repositories or packages. To get lists of all products, patterns, packages or patches available, use the following commands:

zypper products
zypper patterns
zypper packages
zypper patches

To query all repositories for certain packages, use search. It works on package names, or, optionally, on package summaries and descriptions. Using the wild cards * and ? with the search term is allowed. By default, the search is not case-sensitive.

zypper search firefox       # simple search for "firefox"
zypper search "*fire*"      # using wild cards
zypper search -d fire       # also search in package descriptions and summaries
zypper search -u firefox    # only display packages not already installed

To search for packages which provide a special capability, use the command what-provides. For example, if you would like to know which package provides the perl module SVN::Core, use the following command:

zypper what-provides 'perl(SVN::Core)'

To query single packages, use info with an exact package name as an argument. It displays detailed information about a package. To also show what is required/recommended by the package, use the options --requires and --recommends:

zypper info --requires MozillaFirefox

The what-provides package is similar to rpm -q --whatprovides package, but RPM is only able to query the RPM database (that is the database of all installed packages). Zypper, on the other hand, will tell you about providers of the capability from any repository, not only those that are installed.

6.1.7. Configuring Zypper

Zypper now comes with a configuration file, allowing you to permanently change Zypper's behavior (either system-wide or user-specific). For system-wide changes, edit /etc/zypp/zypper.conf. For user-specific changes, edit ~/.zypper.conf. If ~/.zypper.conf does not yet exist, you can use /etc/zypp/zypper.conf as template: copy it to ~/.zypper.conf and adjust it to your liking. Refer to the comments in the file for help about the available options.

6.1.8. Troubleshooting

In case you have problems to access packages from configured repositories (for example, Zypper cannot find a certain package though you know that it exists in one the repositories), it can help to refresh the repositories with:

zypper refresh

If that does not help, try

zypper refresh -fdb

This forces a complete refresh and rebuild of the database, including a forced download of raw metadata.

6.1.9. Zypper Rollback Feature on btrfs File System

If the btrfs file system is used on the root partition and snapper is installed, Zypper automatically calls snapper (via script installed by snapper) when committing changes to the file system to create appropriate file system snapshots. These snapshots can be used for reverting any changes made by zypper. For more information about snapper, see man snapper.

Zypper (and YaST) currently only make snapshots of the root file system. Other subvolumes cannot be configured. This feature is not supported on the default file system.

6.2. RPM—the Package Manager

RPM (RPM Package Manager) is used for managing software packages. Its main commands are rpm and rpmbuild. The powerful RPM database can be queried by the users, system administrators and package builders for detailed information about the installed software.

Essentially, rpm has five modes: installing, uninstalling (or updating) software packages, rebuilding the RPM database, querying RPM bases or individual RPM archives, integrity checking of packages and signing packages. rpmbuild can be used to build installable packages from pristine sources.

Installable RPM archives are packed in a special binary format. These archives consist of the program files to install and certain meta information used during the installation by rpm to configure the software package or stored in the RPM database for documentation purposes. RPM archives normally have the extension .rpm.

[Tip]Software Development Packages

For a number of packages, the components needed for software development (libraries, headers, include files, etc.) have been put into separate packages. These development packages are only needed if you want to compile software yourself (for example, the most recent GNOME packages). They can be identified by the name extension -devel, such as the packages alsa-devel, gimp-devel, and libkde4-devel.

6.2.1. Verifying Package Authenticity

RPM packages have a GPG signature. To verify the signature of an RPM package, use the command rpm --checksig package-1.2.3.rpm to determine whether the package originates from Novell/SUSE or from another trustworthy facility. This is especially recommended for update packages from the Internet.

6.2.2. Managing Packages: Install, Update, and Uninstall

Normally, the installation of an RPM archive is quite simple: rpm -i package.rpm. With this command the package is installed, but only if its dependencies are fulfilled and if there are no conflicts with other packages. With an error message, rpm requests those packages that need to be installed to meet dependency requirements. In the background, the RPM database ensures that no conflicts arise—a specific file can only belong to one package. By choosing different options, you can force rpm to ignore these defaults, but this is only for experts. Otherwise, you risk compromising the integrity of the system and possibly jeopardize the ability to update the system.

The options -U or --upgrade and -F or --freshen can be used to update a package (for example, rpm -F package.rpm). This command removes the files of the old version and immediately installs the new files. The difference between the two versions is that -U installs packages that previously did not exist in the system, but -F merely updates previously installed packages. When updating, rpm updates configuration files carefully using the following strategy:

  • If a configuration file was not changed by the system administrator, rpm installs the new version of the appropriate file. No action by the system administrator is required.

  • If a configuration file was changed by the system administrator before the update, rpm saves the changed file with the extension .rpmorig or .rpmsave (backup file) and installs the version from the new package (but only if the originally installed file and the newer version are different). If this is the case, compare the backup file (.rpmorig or .rpmsave) with the newly installed file and make your changes again in the new file. Afterwards, be sure to delete all .rpmorig and .rpmsave files to avoid problems with future updates.

  • .rpmnew files appear if the configuration file already exists and if the noreplace label was specified in the .spec file.

Following an update, .rpmsave and .rpmnew files should be removed after comparing them, so they do not obstruct future updates. The .rpmorig extension is assigned if the file has not previously been recognized by the RPM database.

Otherwise, .rpmsave is used. In other words, .rpmorig results from updating from a foreign format to RPM. .rpmsave results from updating from an older RPM to a newer RPM. .rpmnew does not disclose any information as to whether the system administrator has made any changes to the configuration file. A list of these files is available in /var/adm/rpmconfigcheck. Some configuration files (like /etc/httpd/httpd.conf) are not overwritten to allow continued operation.

The -U switch is not just an equivalent to uninstalling with the -e option and installing with the -i option. Use -U whenever possible.

To remove a package, enter rpm -e package. rpm, which only deletes the package if there are no unresolved dependencies. It is theoretically impossible to delete Tcl/Tk, for example, as long as another application requires it. Even in this case, RPM calls for assistance from the database. If such a deletion is, for whatever reason, impossible (even if no additional dependencies exist), it may be helpful to rebuild the RPM database using the option --rebuilddb.

6.2.3. RPM and Patches

To guarantee the operational security of a system, update packages must be installed in the system from time to time. Previously, a bug in a package could only be eliminated by replacing the entire package. Large packages with bugs in small files could easily result in this scenario. However the SUSE RPM offers a feature enabling the installation of patches in packages.

The most important considerations are demonstrated using pine as an example:

Is the patch RPM suitable for my system?

To check this, first query the installed version of the package. For pine, this can be done with

rpm -q pine
pine-4.44-188

Then check if the patch RPM is suitable for this version of pine:

rpm -qp --basedon pine-4.44-224.i586.patch.rpm 
pine = 4.44-188
pine = 4.44-195
pine = 4.44-207

This patch is suitable for three different versions of pine. The installed version in the example is also listed, so the patch can be installed.

Which files are replaced by the patch?

The files affected by a patch can easily be seen in the patch RPM. The rpm parameter -P allows selection of special patch features. Display the list of files with the following command:

rpm -qpPl pine-4.44-224.i586.patch.rpm
/etc/pine.conf
/etc/pine.conf.fixed
/usr/bin/pine

or, if the patch is already installed, with the following command:

rpm -qPl pine
/etc/pine.conf
/etc/pine.conf.fixed
/usr/bin/pine
How can a patch RPM be installed in the system?

Patch RPMs are used just like normal RPMs. The only difference is that a suitable RPM must already be installed.

Which patches are already installed in the system and for which package versions?

A list of all patches installed in the system can be displayed with the command rpm -qPa. If only one patch is installed in a new system (as in this example), the list appears as follows:

rpm -qPa
pine-4.44-224

If, at a later date, you want to know which package version was originally installed, this information is also available in the RPM database. For pine, this information can be displayed with the following command:

rpm -q --basedon pine
pine = 4.44-188

More information, including information about the patch feature of RPM, is available in the man pages of rpm and rpmbuild.

[Note]Official Updates for SUSE Linux Enterprise Server

In order to make the download size of updates as small as possible, official updates for SUSE Linux Enterprise Server are not provided as Patch RPMs, but as Delta RPM packages. For details, see Section 6.2.4, “Delta RPM Packages”.

6.2.4. Delta RPM Packages

Delta RPM packages contain the difference between an old and a new version of an RPM package. Applying a delta RPM onto an old RPM results in a completely new RPM. It is not necessary to have a copy of the old RPM because a delta RPM can also work with an installed RPM. The delta RPM packages are even smaller in size than patch RPMs, which is an advantage when transferring update packages over the Internet. The drawback is that update operations with delta RPMs involved consume considerably more CPU cycles than plain or patch RPMs.

The prepdeltarpm, writedeltarpm and applydeltarpm binaries are part of the delta RPM suite (package deltarpm) and help you create and apply delta RPM packages. With the following commands, create a delta RPM called new.delta.rpm. The following command assumes that old.rpm and new.rpm are present:

prepdeltarpm -s seq -i info old.rpm > old.cpio
prepdeltarpm -f new.rpm > new.cpio
xdelta delta -0 old.cpio new.cpio delta
writedeltarpm new.rpm delta info new.delta.rpm

Finally, remove the temporary working files old.cpio, new.cpio, and delta.

Using applydeltarpm, you can reconstruct the new RPM from the file system if the old package is already installed:

applydeltarpm new.delta.rpm new.rpm

To derive it from the old RPM without accessing the file system, use the -r option:

applydeltarpm -r old.rpm new.delta.rpm new.rpm

See /usr/share/doc/packages/deltarpm/README for technical details.

6.2.5. RPM Queries

With the -q option rpm initiates queries, making it possible to inspect an RPM archive (by adding the option -p) and also to query the RPM database of installed packages. Several switches are available to specify the type of information required. See Table 6.1, “The Most Important RPM Query Options”.

Table 6.1. The Most Important RPM Query Options

-i

Package information

-l

File list

-f FILE

Query the package that contains the file FILE (the full path must be specified with FILE)

-s

File list with status information (implies -l)

-d

List only documentation files (implies -l)

-c

List only configuration files (implies -l)

--dump

File list with complete details (to be used with -l, -c, or -d)

--provides

List features of the package that another package can request with --requires

--requires, -R

Capabilities the package requires

--scripts

Installation scripts (preinstall, postinstall, uninstall)


For example, the command rpm -q -i wget displays the information shown in Example 6.2, “rpm -q -i wget”.

Example 6.2. rpm -q -i wget

Name        : wget                         Relocations: (not relocatable)
Version     : 1.11.4                            Vendor: openSUSE
Release     : 1.70                          Build Date: Sat 01 Aug 2009 09:49:48 CEST
Install Date: Thu 06 Aug 2009 14:53:24 CEST      Build Host: build18
Group       : Productivity/Networking/Web/Utilities   Source RPM: wget-1.11.4-1.70.src.rpm
Size        : 1525431                          License: GPL v3 or later
Signature   : RSA/8, Sat 01 Aug 2009 09:50:04 CEST, Key ID b88b2fd43dbdc284
Packager    : http://bugs.opensuse.org
URL         : http://www.gnu.org/software/wget/
Summary     : A Tool for Mirroring FTP and HTTP Servers
Description :
Wget enables you to retrieve WWW documents or FTP files from a server.
This can be done in script files or via the command line.
[...]

The option -f only works if you specify the complete filename with its full path. Provide as many filenames as desired. For example, the following command

rpm -q -f /bin/rpm /usr/bin/wget

results in:

rpm-4.8.0-4.3.x86_64
wget-1.11.4-11.18.x86_64

If only part of the filename is known, use a shell script as shown in Example 6.3, “Script to Search for Packages”. Pass the partial filename to the script shown as a parameter when running it.

Example 6.3. Script to Search for Packages

#! /bin/sh
for i in $(rpm -q -a -l | grep $1); do
    echo "\"$i\" is in package:"
    rpm -q -f $i
    echo ""
done

The command rpm -q --changelog rpm displays a detailed list of change information about a specific package (in this case, the rpmpackage), sorted by date.

With the help of the installed RPM database, verification checks can be made. Initiate these with -V, -y or --verify. With this option, rpm shows all files in a package that have been changed since installation. rpm uses eight character symbols to give some hints about the following changes:

Table 6.2. RPM Verify Options

5

MD5 check sum

S

File size

L

Symbolic link

T

Modification time

D

Major and minor device numbers

U

Owner

G

Group

M

Mode (permissions and file type)


In the case of configuration files, the letter c is printed. For example, for changes to /etc/wgetrc (wget package):

rpm -V wget
S.5....T c /etc/wgetrc

The files of the RPM database are placed in /var/lib/rpm. If the partition /usr has a size of 1 GB, this database can occupy nearly 30 MB, especially after a complete update. If the database is much larger than expected, it is useful to rebuild the database with the option --rebuilddb. Before doing this, make a backup of the old database. The cron script cron.daily makes daily copies of the database (packed with gzip) and stores them in /var/adm/backup/rpmdb. The number of copies is controlled by the variable MAX_RPMDB_BACKUPS (default: 5) in /etc/sysconfig/backup. The size of a single backup is approximately 1 MB for 1 GB in /usr.

6.2.6. Installing and Compiling Source Packages

All source packages carry a .src.rpm extension (source RPM).

[Note]Installed Source Packages

Source packages can be copied from the installation medium to the hard disk and unpacked with YaST. They are not, however, marked as installed ([i]) in the package manager. This is because the source packages are not entered in the RPM database. Only installed operating system software is listed in the RPM database. When you install a source package, only the source code is added to the system.

The following directories must be available for rpm and rpmbuild in /usr/src/packages (unless you specified custom settings in a file like /etc/rpmrc):

SOURCES

for the original sources (.tar.bz2 or .tar.gz files, etc.) and for distribution-specific adjustments (mostly .diff or .patch files)

SPECS

for the .spec files, similar to a meta Makefile, which control the build process

BUILD

all the sources are unpacked, patched and compiled in this directory

RPMS

where the completed binary packages are stored

SRPMS

here are the source RPMs

When you install a source package with YaST, all the necessary components are installed in /usr/src/packages: the sources and the adjustments in SOURCES and the relevant .spec file in SPECS.

[Warning]

Do not experiment with system components (glibc, rpm, sysvinit, etc.), because this endangers the stability of your system.

The following example uses the wget.src.rpm package. After installing the source package, you should have files similar to those in the following list:

/usr/src/packages/SOURCES/wget-1.11.4.tar.bz2
/usr/src/packages/SOURCES/wgetrc.patch
/usr/src/packages/SPECS/wget.spec

rpmbuild -bX /usr/src/packages/SPECS/wget.spec starts the compilation. X is a wild card for various stages of the build process (see the output of --help or the RPM documentation for details). The following is merely a brief explanation:

-bp

Prepare sources in /usr/src/packages/BUILD: unpack and patch.

-bc

Do the same as -bp, but with additional compilation.

-bi

Do the same as -bp, but with additional installation of the built software. Caution: if the package does not support the BuildRoot feature, you might overwrite configuration files.

-bb

Do the same as -bi, but with the additional creation of the binary package. If the compile was successful, the binary should be in /usr/src/packages/RPMS.

-ba

Do the same as -bb, but with the additional creation of the source RPM. If the compilation was successful, the binary should be in /usr/src/packages/SRPMS.

--short-circuit

Skip some steps.

The binary RPM created can now be installed with rpm -i or, preferably, with rpm -U. Installation with rpm makes it appear in the RPM database.

6.2.7. Compiling RPM Packages with build

The danger with many packages is that unwanted files are added to the running system during the build process. To prevent this use build, which creates a defined environment in which the package is built. To establish this chroot environment, the build script must be provided with a complete package tree. This tree can be made available on the hard disk, via NFS, or from DVD. Set the position with build --rpms directory. Unlike rpm, the build command looks for the .spec file in the source directory. To build wget (like in the above example) with the DVD mounted in the system under /media/dvd, use the following commands as root:

cd /usr/src/packages/SOURCES/
mv ../SPECS/wget.spec .
build --rpms /media/dvd/suse/ wget.spec

Subsequently, a minimum environment is established at /var/tmp/build-root. The package is built in this environment. Upon completion, the resulting packages are located in /var/tmp/build-root/usr/src/packages/RPMS.

The build script offers a number of additional options. For example, cause the script to prefer your own RPMs, omit the initialization of the build environment or limit the rpm command to one of the above-mentioned stages. Access additional information with build --help and by reading the build man page.

6.2.8. Tools for RPM Archives and the RPM Database

Midnight Commander (mc) can display the contents of RPM archives and copy parts of them. It represents archives as virtual file systems, offering all usual menu options of Midnight Commander. Display the HEADER with F3. View the archive structure with the cursor keys and Enter. Copy archive components with F5.

A full-featured package manager is available as a YaST module. For details, see Chapter 9, Installing or Removing Software (↑Deployment Guide).

Chapter 7. Bash and Bash Scripts

Abstract

These days many people use computers with a graphical user interface (GUI) like KDE or GNOME. Although they offer lots of features, their use is limited when it comes to the execution of automatical tasks. Shells are a good addition to GUIs and this chapter gives you an overview of some aspects of shells, in this case Bash.

7.1. What is The Shell?

Traditionally, the shell is Bash (Bourne again Shell). When this chapter speaks about the shell it means Bash. There are actually more available shells than Bash (ash, csh, ksh, zsh, …), each employing different features and characteristics. If you need further information about other shells, search for shell in YaST.

7.1.1. Knowing The Bash Configuration Files

A shell can be invoked as an:

  1. Interactive login shell.  This is used when logging in to a machine, invoking Bash with the --login option or when logging in to a remote machine with SSH.

  2. Ordinary interactive shell.  This is normally the case when starting xterm, konsole, gnome-terminal or similar tools.

  3. Non-interactive shell.  This is used when invoking a shell script at the command line.

Depending on which type of shell you use, different configuration files are being read. The following tables show the login and non-login shell configuration files.

Table 7.1. Bash Configuration Files for Login Shells

File

Description

/etc/profile

Do not modify this file, otherwise your modifications can be destroyed during your next update!

/etc/profile.local

Use this file if you extend /etc/profile

/etc/profile.d/

Contains system-wide configuration files for specific programs

~/.profile

Insert user specific configuration for login shells here


Table 7.2. Bash Configuration Files for Non-Login Shells

/etc/bash.bashrc

Do not modify this file, otherwise your modifications can be destroyed during your next update!

/etc/bash.bashrc.local

Use this file to insert your system-wide modifications for Bash only

~/.bashrc

Insert user specific configuration here


Additionally, Bash uses some more files:

Table 7.3. Special Files for Bash

File

Description

~/.bash_history

Contains a list of all commands you have been typing

~/.bash_logout

Executed when logging out


7.1.2. The Directory Structure

The following table provides a short overview of the most important higher-level directories that you find on a Linux system. Find more detailed information about the directories and important subdirectories in the following list.

Table 7.4. Overview of a Standard Directory Tree

Directory

Contents

/

Root directory—the starting point of the directory tree.

/bin

Essential binary files, such as commands that are needed by both the system administrator and normal users. Usually also contains the shells, such as Bash.

/boot

Static files of the boot loader.

/dev

Files needed to access host-specific devices.

/etc

Host-specific system configuration files.

/home

Holds the home directories of all users who have accounts on the system. However, root's home directory is not located in /home but in /root.

/lib

Essential shared libraries and kernel modules.

/media

Mount points for removable media.

/mnt

Mount point for temporarily mounting a file system.

/opt

Add-on application software packages.

/root

Home directory for the superuser root.

/sbin

Essential system binaries.

/srv

Data for services provided by the system.

/tmp

Temporary files.

/usr

Secondary hierarchy with read-only data.

/var

Variable data such as log files.

/windows

Only available if you have both Microsoft Windows* and Linux installed on your system. Contains the Windows data.


The following list provides more detailed information and gives some examples of which files and subdirectories can be found in the directories:

/bin

Contains the basic shell commands that may be used both by root and by other users. These commands include ls, mkdir, cp, mv, rm and rmdir. /bin also contains Bash, the default shell in SUSE Linux Enterprise Server.

/boot

Contains data required for booting, such as the boot loader, the kernel, and other data that is used before the kernel begins executing user-mode programs.

/dev

Holds device files that represent hardware components.

/etc

Contains local configuration files that control the operation of programs like the X Window System. The /etc/init.d subdirectory contains scripts that are executed during the boot process.

/home/username

Holds the private data of every user who has an account on the system. The files located here can only be modified by their owner or by the system administrator. By default, your e-mail directory and personal desktop configuration are located here in the form of hidden files and directories. KDE users find the personal configuration data for their desktop in .kde4, GNOME users find it in .gconf.

[Note]Home Directory in a Network Environment

If you are working in a network environment, your home directory may be mapped to a directory in the file system other than /home.

/lib

Contains the essential shared libraries needed to boot the system and to run the commands in the root file system. The Windows equivalent for shared libraries are DLL files.

/media

Contains mount points for removable media, such as CD-ROMs, USB sticks and digital cameras (if they use USB). /media generally holds any type of drive except the hard drive of your system. As soon as your removable medium has been inserted or connected to the system and has been mounted, you can access it from here.

/mnt

This directory provides a mount point for a temporarily mounted file system. root may mount file systems here.

/opt

Reserved for the installation of third-party software. Optional software and larger add-on program packages can be found here.

/root

Home directory for the root user. The personal data of root is located here.

/sbin

As the s indicates, this directory holds utilities for the superuser. /sbin contains the binaries essential for booting, restoring and recovering the system in addition to the binaries in /bin.

/srv

Holds data for services provided by the system, such as FTP and HTTP.

/tmp

This directory is used by programs that require temporary storage of files.

[Important]Cleaning up /tmp at Boot Time

Data stored in /tmp are not guaranteed to survive a system reboot. It depends, for example, on settings in /etc/sysconfig/cron.

/usr

/usr has nothing to do with users, but is the acronym for UNIX system resources. The data in /usr is static, read-only data that can be shared among various hosts compliant with the Filesystem Hierarchy Standard (FHS). This directory contains all application programs and establishes a secondary hierarchy in the file system. KDE4 and GNOME are also located here. /usr holds a number of subdirectories, such as /usr/bin, /usr/sbin, /usr/local, and /usr/share/doc.

/usr/bin

Contains generally accessible programs.

/usr/sbin

Contains programs reserved for the system administrator, such as repair functions.

/usr/local

In this directory the system administrator can install local, distribution-independent extensions.

/usr/share/doc

Holds various documentation files and the release notes for your system. In the manual subdirectory find an online version of this manual. If more than one language is installed, this directory may contain versions of the manuals for different languages.

Under packages find the documentation included in the software packages installed on your system. For every package, a subdirectory /usr/share/doc/packages/packagename is created that often holds README files for the package and sometimes examples, configuration files or additional scripts.

If HOWTOs are installed on your system /usr/share/doc also holds the howto subdirectory in which to find additional documentation on many tasks related to the setup and operation of Linux software.

/var

Whereas /usr holds static, read-only data, /var is for data which is written during system operation and thus is variable data, such as log files or spooling data. For an overview of the most important log files you can find under /var/log/, refer to Table 35.1, “Log Files”.

7.2. Writing Shell Scripts

Shell scripts are a convenient way of doing all sorts of tasks: collecting data, searching for a word or phrase in a text and many other useful things. The following example shows a small shell script that prints a text:

Example 7.1. A Shell Script Printing a Text

#!/bin/sh 1
# Output the following line: 2
echo "Hello World" 3

1

The first line begins with the Shebang characters (#!) which is an indicator that this file is a script. The script is executed with the specified interpreter after the Shebang, in this case /bin/sh.

2

The second line is a comment beginning with the hash sign. It is recommended to comment difficult lines to remember what they do.

3

The third line uses the built-in command echo to print the corresponding text.


Before you can run this script you need some prerequisites:

  1. Every script should contain a Shebang line (this is already the case with our example above.) If a script does not have this line, you have to call the interpreter manually.

  2. You can save the script wherever you want. However, it is a good idea to save it in a directory where the shell can find it. The search path in a shell is determined by the environment variable PATH. Usually a normal user does not have write access to /usr/bin. Therefore it is recommended to save your scripts in the users' directory ~/bin/. The above example gets the name hello.sh.

  3. The script needs executable permissions. Set the permissions with the following command:

    chmod +x ~/bin/hello.sh

If you have fullfilled all of the above prerequisites, you can execute the script in the following ways:

  1. As Absolute Path.  The script can be executed with an absolute path. In our case, it is ~/bin/hello.sh.

  2. Everywhere.  If the PATH environment variable contains the directory where the script is located, you can execute the script just with hello.sh.

7.3. Redirecting Command Events

Each command can use three channels, either for input or output:

  • Standard Output.  This is the default output channel. Whenever a command prints something, it uses the standard output channel.

  • Standard Input.  If a command needs input from users or other commands, it uses this channel.

  • Standard Error.  Commands use this channel for error reporting.

To redirect these channels, there are the following possibilities:

Command > File

Saves the output of the command into a file, an existing file will be deleted. For example, the ls command writes its output into the file listing.txt:

ls > listing.txt
Command >> File

Appends the output of the command to a file. For example, the ls command appends its output to the file listing.txt:

ls >> listing.txt
Command < File

Reads the file as input for the given command. For example, the read command reads in the content of the file into the variable:

read a < foo
Command1 | Command2

Redirects the output of the left command as input for the right command. For example, the cat command outputs the content of the /proc/cpuinfo file. This output is used by grep to filter only those lines which contain cpu:

cat /proc/cpuinfo | grep cpu

Every channel has a file descriptor: 0 (zero) for standard input, 1 for standard output and 2 for standard error. It is allowed to insert this file descriptor before a < or > character. For example, the following line searches for a file starting with foo, but suppresses its errors by redirecting it to /dev/null:

find / -name "foo*" 2>/dev/null

7.4. Using Aliases

An alias is a shortcut definition of one or more commands. The syntax for an alias is:

alias NAME=DEFINITION

For example, the following line defines an alias lt which outputs a long listing (option -l), sorts it by modification time (-t) and prints it in reverse order while sorting (-r):

alias lt='ls -ltr'

To view all alias definitions, use alias. Remove your alias with unalias and the corresponding alias name.

7.5. Using Variables in Bash

A shell variable can be global or local. Global variables, or environment variables, can be accessed in all shells. In contrast, local variables are visible in the current shell only.

To view all environment variables, use the printenv command. If you need to know the value of a variable, insert the name of your variable as an argument:

printenv PATH

A variable, be it global or local, can also be viewed with echo:

echo $PATH

To set a local variable, use a variable name followed by the equal sign, followed by the value:

PROJECT="SLED"

Do not insert spaces around the equal sign, otherwise you get an error. To set a environment variable, use export:

export NAME="tux"

To remove a variable, use unset:

unset NAME

The following table contains some common environment variables which can be used in you shell scripts:

Table 7.5. Useful Environment Variables

HOME

the home directory of the current user

HOST

the current hostname

LANG

when a tool is localized, it uses the language from this environment variable. English can also be set to C

PATH

the search path of the shell, a list of directories separated by colon

PS1

specifies the normal prompt printed before each command

PS2

specifies the secondary prompt printed when you execute a multi-line command

PWD

current working directory

USER

the current user


7.5.1. Using Argument Variables

For example, if you have the script foo.sh you can execute it like this:

foo.sh "Tux Penguin" 2000 

To access all the arguments which are passed to your script, you need positional parameters. These are $1 for the first argument, $2 for the second, and so on. You can have up to nine parameters. To get the script name, use $0.

The following script foo.sh prints all arguments from 1 to 4:

#!/bin/sh
echo \"$1\" \"$2\" \"$3\" \"$4\"

If you execute this script with the above arguments, you get:

"Tux Penguin" "2000" "" ""

7.5.2. Using Variable Substitution

Variable substitutions apply a pattern to the content of a variable either from the left or right side. The following list contains the possible syntax forms:

${VAR#pattern}

removes the shortest possible match from the left:

file=/home/tux/book/book.tar.bz2
echo ${file#*/}
home/tux/book/book.tar.bz2
${VAR##pattern}

removes the longest possible match from the left:

file=/home/tux/book/book.tar.bz2
echo ${file##*/}
book.tar.bz2
${VAR%pattern}

removes the shortest possible match from the right:

file=/home/tux/book/book.tar.bz2
echo ${file%.*}
/home/tux/book/book.tar
${VAR%%pattern}

removes the longest possible match from the right:

file=/home/tux/book/book.tar.bz2
echo ${file%%.*}
/home/tux/book/book
${VAR/pattern_1/pattern_2}

substitutes the content of VAR from the pattern_1 with pattern_2:

file=/home/tux/book/book.tar.bz2
echo ${file/tux/wilber}
/home/wilber/book/book.tar.bz2

7.6. Grouping And Combining Commands

Shells allow you to concatenate and group commands for conditional execution. Each command returns an exit code which determines the success or failure of its operation. If it is 0 (zero) the command was successful, everything else marks an error which is specific to the command.

The following list shows, how commands can be grouped:

Command1 ; Command2

executes the commands in sequential order. The exit code is not checked. The following line displays the content of the file with cat and then prints its file properties with ls regardless of their exit codes:

cat filelist.txt ; ls -l filelist.txt
Command1 && Command2

runs the right command, if the left command was successful (logical AND). The following line displays the content of the file and prints its file properties only, when the previous command was successful (compare it with the previous entry in this list):

cat filelist.txt && ls -l filelist.txt
Command1 || Command2

runs the right command, when the left command has failed (logical OR). The following line creates only a directory in /home/wilber/bar when the creation of the directory in /home/tux/foo has failed:

mkdir /home/tux/foo || mkdir /home/wilber/bar
funcname() { ... }

creates a shell function. You can use the positional parameters to access its arguments. The following line defines the function hello to print a short message:

hello() { echo "Hello $1"; }

You can call this function like this:

hello Tux

which prints:

Hello Tux

7.7. Working with Common Flow Constructs

To control the flow of your script, a shell has while, if, for and case constructs.

7.7.1. The if Control Command

The if command is used to check expressions. For example, the following code tests whether the current user is Tux:

if test $USER = "tux"; then
  echo "Hello Tux."
else
  echo "You are not Tux."
fi

The test expression can be as complex or simple as possible. The following expression checks if the file foo.txt exists:

if test -e /tmp/foo.txt ;
then
  echo "Found foo.txt"
fi

The test expression can also be abbreviated in angled brackets:

if [ -e /tmp/foo.txt ] ; then
  echo "Found foo.txt"
fi

Find more useful expressions at http://www.cyberciti.biz/nixcraft/linux/docs/uniqlinuxfeatures/lsst/ch03sec02.html.

7.7.2. Creating Loops With The For Command

The for loop allows you to execute commands to a list of entries. For example, the following code prints some information about PNG files in the current directory:

for i in *.png; do
 ls -l $i
done

7.8. For More Information

Important information about Bash is provided in the man pages man sh. More about this topic can be found in the following list:

Part II. System

Contents

8. 32-Bit and 64-Bit Applications in a 64-Bit System Environment
8.1. Runtime Support
8.2. Software Development
8.3. Software Compilation on Biarch Platforms
8.4. Kernel Specifications
9. Booting and Configuring a Linux System
9.1. The Linux Boot Process
9.2. The init Process
9.3. System Configuration via /etc/sysconfig
10. The Boot Loader GRUB
10.1. Booting with GRUB
10.2. Configuring the Boot Loader with YaST
10.3. Uninstalling the Linux Boot Loader
10.4. Creating Boot CDs
10.5. The Graphical SUSE Screen
10.6. Troubleshooting
10.7. For More Information
11. UEFI (Unified Extensible Firmware Interface)
11.1. Secure Boot
11.2. For More Information
12. Special System Features
12.1. Information about Special Software Packages
12.2. Virtual Consoles
12.3. Keyboard Mapping
12.4. Language and Country-Specific Settings
13. Printer Operation
13.1. The Workflow of the Printing System
13.2. Methods and Protocols for Connecting Printers
13.3. Installing the Software
13.4. Network Printers
13.5. Printing from the Command Line
13.6. Special Features in SUSE Linux Enterprise Server
13.7. Troubleshooting
14. Dynamic Kernel Device Management with udev
14.1. The /dev Directory
14.2. Kernel uevents and udev
14.3. Drivers, Kernel Modules and Devices
14.4. Booting and Initial Device Setup
14.5. Monitoring the Running udev Daemon
14.6. Influencing Kernel Device Event Handling with udev Rules
14.7. Persistent Device Naming
14.8. Files used by udev
14.9. For More Information
15. The X Window System
15.1. Manually Configuring the X Window System
15.2. Installing and Configuring Fonts
15.3. For More Information
16. Accessing File Systems with FUSE
16.1. Configuring FUSE
16.2. Available FUSE Plug-ins
16.3. For More Information

Chapter 8. 32-Bit and 64-Bit Applications in a 64-Bit System Environment

SUSE® Linux Enterprise Server is available for several 64-bit platforms. This does not necessarily mean that all the applications included have already been ported to 64-bit platforms. SUSE Linux Enterprise Server supports the use of 32-bit applications in a 64-bit system environment. This chapter offers a brief overview of how this support is implemented on 64-bit SUSE Linux Enterprise Server platforms. It explains how 32-bit applications are executed (runtime support) and how 32-bit applications should be compiled to enable them to run both in 32-bit and 64-bit system environments. Additionally, find information about the kernel API and an explanation of how 32-bit applications can run under a 64-bit kernel.

SUSE Linux Enterprise Server for the 64-bit platforms ia64, ppc64, System z and x86_64 is designed so that existing 32-bit applications run in the 64-bit environment out-of-the-box. The corresponding 32-bit platforms are x86 for ia64, ppc for ppc64, and x86 for x86_64. This support means that you can continue to use your preferred 32-bit applications without waiting for a corresponding 64-bit port to become available. The current ppc64 system runs most applications in 32-bit mode, but you can run 64-bit applications.

8.1. Runtime Support

[Important]Conflicts between Application Versions

If an application is available both for 32-bit and 64-bit environments, parallel installation of both versions is bound to lead to problems. In such cases, decide on one of the two versions and install and use this.

An exception to this rule is PAM (pluggable authentication modules). SUSE Linux Enterprise Server uses PAM in the authentication process as a layer that mediates between user and application. On a 64-bit operating system that also runs 32-bit applications it is necessary to always install both versions of a PAM module.

To be executed correctly, every application requires a range of libraries. Unfortunately, the names for the 32-bit and 64-bit versions of these libraries are identical. They must be differentiated from each other in another way.

To retain compatibility with the 32-bit version, the libraries are stored at the same place in the system as in the 32-bit environment. The 32-bit version of libc.so.6 is located under /lib/libc.so.6 in both the 32-bit and 64-bit environments.

All 64-bit libraries and object files are located in directories called lib64. The 64-bit object files that you would normally expect to find under /lib and /usr/lib are now found under /lib64 and /usr/lib64. This means that there is space for the 32-bit libraries under /lib and /usr/lib, so the filename for both versions can remain unchanged.

Subdirectories of 32-bit /lib directories which contain data content that does not depend on the word size are not moved. This scheme conforms to LSB (Linux Standards Base) and FHS (File System Hierarchy Standard).

►ipf: The 64-bit libraries for ia64 are located in the standard lib directories, there is neither a lib64 directory nor a lib32 directory. ia64 executes 32-bit x86 code under an emulation. A set of basic libraries is installed in /emul/ia32-linux/lib and /emul/ia32-linux/usr/lib.

8.2. Software Development

All 64-bit architectures support the development of 64-bit objects. The level of support for 32-bit compiling depends on the architecture. These are the various implementation options for the tool chain from GCC (GNU Compiler Collection) and binutils, which include the assembler as and the linker ld:

Biarch Compiler

Both 32-bit and 64-bit objects can be generated with a biarch development tool chain. A biarch development tool chain allows generation of 32-bit and 64-bit objects. The compilation of 64-bit objects is the default on almost all platforms. 32-bit objects can be generated if special flags are used. This special flag is -m32 for GCC. The flags for the binutils are architecture-dependent, but GCC transfers the correct flags to linkers and assemblers. A biarch development tool chain currently exists for amd64 (supports development for x86 and amd64 instructions), for System z and for ppc64. 32-bit objects are normally created on the ppc64 platform. The -m64 flag must be used to generate 64-bit objects.

No Support

SUSE Linux Enterprise Server does not support the direct development of 32-bit software on all platforms. To develop applications for x86 under ia64, use the corresponding 32-bit version of SUSE Linux Enterprise Server.

All header files must be written in an architecture-independent form. The installed 32-bit and 64-bit libraries must have an API (application programming interface) that matches the installed header files. The normal SUSE Linux Enterprise Server environment is designed according to this principle. In the case of manually updated libraries, resolve these issues yourself.

8.3. Software Compilation on Biarch Platforms

To develop binaries for the other architecture on a biarch architecture, the respective libraries for the second architecture must additionally be installed. These packages are called rpmname-32bit or rpmname-x86 (for ia64) if the second architecture is a 32-bit architecture or rpmname-64bit if the second architecture is a 64-bit architecture. You also need the respective headers and libraries from the rpmname-devel packages and the development libraries for the second architecture from rpmname-devel-32bit or rpmname-devel-64bit.

For example, to compile a program that uses libaio on a system whose second architecture is a 32-bit architecture (x86_64 or System z), you need the following RPMs:

libaio-32bit

32-bit runtime package

libaio-devel-32bit

Headers and libraries for 32-bit development

libaio

64-bit runtime package

libaio-devel

64-bit development headers and libraries

Most open source programs use an autoconf-based program configuration. To use autoconf for configuring a program for the second architecture, overwrite the normal compiler and linker settings of autoconf by running the configure script with additional environment variables.

The following example refers to an x86_64 system with x86 as the second architecture. Examples for ppc64 with ppc as the second architecture would be similar. This example does not apply to ia64 where you cannot build 32-bit packages.

  1. Use the 32-bit compiler:

    CC="gcc -m32"
  2. Instruct the linker to process 32-bit objects (always use gcc as the linker front-end):

    LD="gcc -m32"
  3. Set the assembler to generate 32-bit objects:

    AS="gcc -c -m32"
  4. Specify linker flags, such as the location of 32-bit libraries, for example:

    LDFLAGS="-L/usr/lib"
  5. Specify the location for the 32-bit object code libraries:

    --libdir=/usr/lib
  6. Specify the location for the 32-bit X libraries:

    --x-libraries=/usr/lib

Not all of these variables are needed for every program. Adapt them to the respective program.

An example configure call to compile a native 32-bit application on x86_64, ppc64 or System z could appear as follows:

CC="gcc -m32"
LDFLAGS="-L/usr/lib;"
./configure --prefix=/usr --libdir=/usr/lib --x-libraries=/usr/lib
make
make install

8.4. Kernel Specifications

The 64-bit kernels for x86_64, ppc64 and System z offer both a 64-bit and a 32-bit kernel ABI (application binary interface). The latter is identical with the ABI for the corresponding 32-bit kernel. This means that the 32-bit application can communicate with the 64-bit kernel in the same way as with the 32-bit kernel.

The 32-bit emulation of system calls for a 64-bit kernel does not support all the APIs used by system programs. This depends on the platform. For this reason, a small number of applications, like lspci, must be compiled on non-ppc64 platforms as 64-bit programs to function properly. On IBM System z, not all ioctls are available in the 32-bit kernel ABI.

A 64-bit kernel can only load 64-bit kernel modules that have been specially compiled for this kernel. It is not possible to use 32-bit kernel modules.

[Tip]Kernel-loadable Modules

Some applications require separate kernel-loadable modules. If you intend to use such a 32-bit application in a 64-bit system environment, contact the provider of this application and SUSE to make sure that the 64-bit version of the kernel-loadable module and the 32-bit compiled version of the kernel API are available for this module.

Chapter 9. Booting and Configuring a Linux System

Abstract

Booting a Linux system involves different components. The hardware itself is initialized by the BIOS, which starts the Kernel by means of a boot loader. After this point, the boot process with init and the runlevels is completely controlled by the operating system. The runlevel concept enables you to maintain setups for everyday usage as well as to perform maintenance tasks on the system.

9.1. The Linux Boot Process

The Linux boot process consists of several stages, each represented by a different component. The following list briefly summarizes the boot process and features all the major components involved.

  1. BIOS.  After turning on the computer, the BIOS initializes the screen and keyboard and tests the main memory. Up to this stage, the machine does not access any mass storage media. Subsequently, the information about the current date, time, and the most important peripherals are loaded from the CMOS values. When the first hard disk and its geometry are recognized, the system control passes from the BIOS to the boot loader. If the BIOS supports network booting, it is also possible to configure a boot server that provides the boot loader. On x86 systems, PXE boot is needed. Other architectures commonly use the BOOTP protocol to get the boot loader.

  2. Boot Loader.  The first physical 512-byte data sector of the first hard disk is loaded into the main memory and the boot loader that resides at the beginning of this sector takes over. The commands executed by the boot loader determine the remaining part of the boot process. Therefore, the first 512 bytes on the first hard disk are referred to as the Master Boot Record (MBR). The boot loader then passes control to the actual operating system, in this case, the Linux Kernel. More information about GRUB, the Linux boot loader, can be found in Chapter 10, The Boot Loader GRUB. For a network boot, the BIOS acts as the boot loader. It gets the image to start from the boot server and starts the system. This is completely independent of local hard disks.

  3. Kernel and initramfs To pass system control, the boot loader loads both the Kernel and an initial RAM–based file system (initramfs) into memory. The contents of the initramfs can be used by the Kernel directly. initramfs contains a small executable called init that handles the mounting of the real root file system. If special hardware drivers are needed before the mass storage can be accessed, they must be in initramfs. For more information about initramfs, refer to Section 9.1.1, “initramfs. If the system does not have a local hard disk, the initramfs must provide the root file system to the Kernel. This can be done with the help of a network block device like iSCSI or SAN, but it is also possible to use NFS as the root device.

  4. init on initramfs This program performs all actions needed to mount the proper root file system, like providing Kernel functionality for the needed file system and device drivers for mass storage controllers with udev. After the root file system has been found, it is checked for errors and mounted. If this is successful, the initramfs is cleaned and the init program on the root file system is executed. For more information about init, refer to Section 9.1.2, “init on initramfs. Find more information about udev in Chapter 14, Dynamic Kernel Device Management with udev.

  5. init init handles the actual booting of the system through several different levels providing different functionality. init is described in Section 9.2, “The init Process”.

9.1.1. initramfs

initramfs is a small cpio archive that the Kernel can load to a RAM disk. It provides a minimal Linux environment that enables the execution of programs before the actual root file system is mounted. This minimal Linux environment is loaded into memory by BIOS routines and does not have specific hardware requirements other than sufficient memory. initramfs must always provide an executable named init that should execute the actual init program on the root file system for the boot process to proceed.

Before the root file system can be mounted and the operating system can be started, the Kernel needs the corresponding drivers to access the device on which the root file system is located. These drivers may include special drivers for certain kinds of hard drives or even network drivers to access a network file system. The needed modules for the root file system may be loaded by init on initramfs. After the modules are loaded, udev provides the initramfs with the needed devices. Later in the boot process, after changing the root file system, it is necessary to regenerate the devices. This is done by boot.udev with the command udevtrigger.

If you need to change hardware (for example hard disks) in an installed system and this hardware requires different drivers to be present in the Kernel at boot time, you must update initramfs. This is done in the same way as with its predecessor, init—by calling mkinitrd. Calling mkinitrd without any argument creates an initramfs. Calling mkinitrd -R creates an init. In SUSE® Linux Enterprise Server, the modules to load are specified by the variable INITRD_MODULES in /etc/sysconfig/kernel. After installation, this variable is automatically set to the correct value. The modules are loaded in exactly the order in which they appear in INITRD_MODULES. This is only important if you rely on the correct setting of the device files /dev/sd?. However, in current systems you also may use the device files below /dev/disk/ that are sorted in several subdirectories, named by-id, by-path and by-uuid, and always represent the same disk. This is also possible at install time by specifying the respective mount option.

[Important]Updating initramfs or init

The boot loader loads initramfs or init in the same way as the Kernel. It is not necessary to reinstall GRUB after updating initramfs or init, because GRUB searches the directory for the right file when booting.

9.1.2. init on initramfs

The main purpose of init on initramfs is to prepare the mounting of and access to the real root file system. Depending on your system configuration, init is responsible for the following tasks.

Loading Kernel Modules

Depending on your hardware configuration, special drivers may be needed to access the hardware components of your computer (the most important component being your hard drive). To access the final root file system, the Kernel needs to load the proper file system drivers.

Providing Block Special Files

For each loaded module, the Kernel generates device events. udev handles these events and generates the required special block files on a RAM file system in /dev. Without those special files, the file system and other devices would not be accessible.

Managing RAID and LVM Setups

If you configured your system to hold the root file system under RAID or LVM, init sets up LVM or RAID to enable access to the root file system later. Find information about RAID and LVM in Chapter 15, Advanced Disk Setup (↑Deployment Guide).

Managing Network Configuration

If you configured your system to use a network-mounted root file system (mounted via NFS), init must make sure that the proper network drivers are loaded and that they are set up to allow access to the root file system.

If the file system resides on a networked block device like iSCSI or SAN, the connection to the storage server is also set up by the initramfs.

When init is called during the initial boot as part of the installation process, its tasks differ from those mentioned above:

Finding the Installation Medium

As you start the installation process, your machine loads an installation Kernel and a special init with the YaST installer on the installation medium. The YaST installer, which is run in a RAM file system, needs to have information about the location of the installation medium to access it and install the operating system.

Initiating Hardware Recognition and Loading Appropriate Kernel Modules

As mentioned in Section 9.1.1, “initramfs, the boot process starts with a minimum set of drivers that can be used with most hardware configurations. init starts an initial hardware scanning process that determines the set of drivers suitable for your hardware configuration. The names of the modules needed for the boot process are written to INITRD_MODULES in /etc/sysconfig/kernel. These names are used to generate a custom initramfs that is needed to boot the system. If the modules are not needed for boot but for coldplug, the modules are written to /etc/sysconfig/hardware/hwconfig-*. All devices that are described with configuration files in this directory are initialized in the boot process.

Loading the Installation System or Rescue System

As soon as the hardware is properly recognized, the appropriate drivers are loaded, and udev creates the special device files, init starts the installation system with the actual YaST installer, or the rescue system.

Starting YaST

Finally, init starts YaST, which starts package installation and system configuration.

9.2. The init Process

The program init is the process with process ID 1. It is responsible for initializing the system in the required way. init is started directly by the Kernel and resists signal 9, which normally kills processes. All other programs are either started directly by init or by one of its child processes.

init is centrally configured in the /etc/inittab file where the runlevels are defined (see Section 9.2.1, “Runlevels”). The file also specifies which services and daemons are available in each of the runlevels. Depending on the entries in /etc/inittab, several scripts are run by init. By default, the first script that is started after booting is /etc/init.d/boot. Once the system initialization phase is finished, the system changes the runlevel to its default runlevel with the /etc/init.d/rc script. For reasons of clarity, these scripts, called init scripts, all reside in the directory /etc/init.d (see Section 9.2.2, “Init Scripts”).

The entire process of starting the system and shutting it down is maintained by init. From this point of view, the Kernel can be considered a background process to maintain all other processes and adjust CPU time and hardware access according to requests from other programs.

9.2.1. Runlevels

In Linux, runlevels define how the system is started and what services are available in the running system. After booting, the system starts as defined in /etc/inittab in the line initdefault. Usually this is 3 or 5. See Table 9.1, “Available Runlevels”. As an alternative, the runlevel can be specified at boot time (by adding the runlevel number at the boot prompt, for instance). Any parameters that are not directly evaluated by the Kernel itself are passed to init. To boot into runlevel 3, just add the single number 3 to the boot prompt.

Table 9.1. Available Runlevels

Runlevel

Description

0

System halt

S or 1

Single user mode

2

Local multiuser mode without remote network (NFS, etc.)

3

Full multiuser mode with network

4

User Defined, this is not used unless the administrator configures this runlevel.

5

Full multiuser mode with network and X display manager—KDM, GDM, or XDM

6

System reboot


[Important]Avoid Runlevel 2 with a Partition Mounted via NFS

You should not use runlevel 2 if your system mounts a partition like /usr via NFS. The system might behave unexpectedly if program files or libraries are missing because the NFS service is not available in runlevel 2 (local multiuser mode without remote network).

To change runlevels while the system is running, enter telinit and the corresponding number as an argument. Only the system administrator is allowed to do this. The following list summarizes the most important commands in the runlevel area.

telinit 1 or shutdown now

The system changes to single user mode. This mode is used for system maintenance and administration tasks.

telinit 3

All essential programs and services (including network) are started and regular users are allowed to log in and work with the system without a graphical environment.

telinit 5

The graphical environment is enabled. Usually a display manager like XDM, GDM or KDM is started. If autologin is enabled, the local user is logged in to the preselected window manager (GNOME or KDE or any other window manager).

telinit 0 or shutdown -h now

The system halts.

telinit 6 or shutdown -r now

The system halts then reboots.

Runlevel 5 is the default runlevel in all SUSE Linux Enterprise Server standard installations. Users are prompted for login with a graphical interface or the default user is logged in automatically.

[Warning]Errors in /etc/inittab May Result in a Faulty System Boot

If /etc/inittab is damaged, the system may not boot properly. Therefore, be extremely careful while editing /etc/inittab. Always let init reread /etc/inittab with the command telinit q before rebooting the machine.

Generally, two things happen when you change runlevels. First, stop scripts of the current runlevel are launched, closing down some programs essential for the current runlevel. Then start scripts of the new runlevel are started. Here, in most cases, a number of programs are started. For example, the following occurs when changing from runlevel 3 to 5:

  1. The administrator (root) requests init to change to a different runlevel by entering telinit 5.

  2. init checks the current runlevel (runlevel) and determines it should start /etc/init.d/rc with the new runlevel as a parameter.

  3. Now rc calls the stop scripts of the current runlevel for which there is no start script in the new runlevel. In this example, these are all the scripts that reside in /etc/init.d/rc3.d (the old runlevel was 3) and start with a K. The number following K specifies the order to run the scripts with the stop parameter, because there are some dependencies to consider.

  4. The last things to start are the start scripts of the new runlevel. In this example, these are in /etc/init.d/rc5.d and begin with an S. Again, the number that follows the S determines the sequence in which the scripts are started.

When changing into the same runlevel as the current runlevel, init only checks /etc/inittab for changes and starts the appropriate steps, for example, for starting a getty on another interface. The same functionality may be achieved with the command telinit q.

9.2.2. Init Scripts

There are two types of scripts in /etc/init.d:

Scripts Executed Directly by init

This is the case only during the boot process or if an immediate system shutdown is initiated (power failure or a user pressing Ctrl+Alt+Del). For IBM System z systems, this is the case only during the boot process or if an immediate system shutdown is initiated (power failure or via signal quiesce). The execution of these scripts is defined in /etc/inittab.

Scripts Executed Indirectly by init

These are run when changing the runlevel and always call the master script /etc/init.d/rc, which guarantees the correct order of the relevant scripts.

All scripts are located in /etc/init.d. Scripts that are run at boot time are called through symbolic links from /etc/init.d/boot.d. Scripts for changing the runlevel are called through symbolic links from one of the subdirectories (/etc/init.d/rc0.d to /etc/init.d/rc6.d). This is just for reasons of clarity and avoids duplicate scripts if they are used in several runlevels. Because every script can be executed as both a start and a stop script, these scripts must understand the parameters start and stop. The scripts also understand the restart, reload, force-reload, and status options. These different options are explained in Table 9.2, “Possible init Script Options”. Scripts that are run directly by init do not have these links. They are run independently from the runlevel when needed.

Table 9.2. Possible init Script Options

Option

Description

start

Start service.

stop

Stop service.

restart

If the service is running, stop it then restart it. If it is not running, start it.

reload

Reload the configuration without stopping and restarting the service.

force-reload

Reload the configuration if the service supports this. Otherwise, do the same as if restart had been given.

status

Show the current status of service.


Links in each runlevel-specific subdirectory make it possible to associate scripts with different runlevels. When installing or uninstalling packages, these links are added and removed with the help of the program insserv (or using /usr/lib/lsb/install_initd, which is a script calling this program). See man 8 insserv for more details.

All of these settings may also be changed with the help of the YaST module. If you need to check the status on the command line, use the tool chkconfig, described in the man 8 chkconfig man page.

A short introduction to the boot and stop scripts launched first or last, respectively, follows as well as an explanation of the maintaining script.

boot

Executed while starting the system directly using init. It is independent of the chosen runlevel and is only executed once. Here, the /proc and /dev/pts file systems are mounted and blogd (boot logging daemon) is activated. If the system is booted for the first time after an update or an installation, the initial system configuration is started.

The blogd daemon is a service started by boot and rc before any other one. It is stopped after the actions triggered by these scripts (running a number of subscripts, for example, making special block files available) are completed. blogd writes any screen output to the log file /var/log/boot.msg, but only if and when /var is mounted read-write. Otherwise, blogd buffers all screen data until /var becomes available. Get further information about blogd with man 8 blogd.

The boot script is also responsible for starting all the scripts in /etc/init.d/boot.d with names that start with S. There, the file systems are checked and loop devices are configured if needed. The system time is also set. If an error occurs while automatically checking and repairing the file system, the system administrator can intervene after first entering the root password. The last executed script is boot.local.

boot.local

Here enter additional commands to execute at boot before changing into a runlevel. It can be compared to AUTOEXEC.BAT on DOS systems.

halt

This script is only executed while changing into runlevel 0 or 6. Here, it is executed either as init or as init. Whether the system shuts down or reboots depends on how halt is called. If special commands are needed during the shutdown, add these to the init script.

rc

This script calls the appropriate stop scripts of the current runlevel and the start scripts of the newly selected runlevel. Like the /etc/init.d/boot script, this script is called from /etc/inittab with the desired runlevel as parameter.

You can create your own scripts and easily integrate them into the scheme described above. For instructions about formatting, naming and organizing custom scripts, refer to the specifications of the LSB and to the man pages of init, init.d, chkconfig, and insserv. Additionally consult the man pages of startproc and killproc.

[Warning]Faulty Init Scripts May Halt Your System

Faulty init scripts may hang your machine up. Edit such scripts with great care and, if possible, subject them to heavy testing in the multiuser environment. Find useful information about init scripts in Section 9.2.1, “Runlevels”.

To create a custom init script for a given program or service, use the file /etc/init.d/skeleton as a template. Save a copy of this file under the new name and edit the relevant program and filenames, paths and other details as needed. You may also need to enhance the script with your own parts, so the correct actions are triggered by the init procedure.

The INIT INFO block at the top is a required part of the script and must be edited. See Example 9.1, “A Minimal INIT INFO Block”.

Example 9.1. A Minimal INIT INFO Block

### BEGIN INIT INFO
# Provides:          FOO
# Required-Start:    $syslog $remote_fs
# Required-Stop:     $syslog $remote_fs
# Default-Start:     3 5
# Default-Stop:      0 1 2 6
# Description:       Start FOO to allow XY and provide YZ
### END INIT INFO

In the first line of the INFO block, after Provides:, specify the name of the program or service controlled by this init script. In the Required-Start: and Required-Stop: lines, specify all services that need to be still running when the service itself is stopped. This information is used later to generate the numbering of script names, as found in the runlevel directories. After Default-Start: and Default-Stop:, specify the runlevels in which the service should automatically be started or stopped. Finally, for Description:, provide a short description of the service in question.

To create the links from the runlevel directories (/etc/init.d/rc?.d/) to the corresponding scripts in /etc/init.d/, enter the command insserv new-script-name. insserv evaluates the INIT INFO header to create the necessary links for start and stop scripts in the runlevel directories (/etc/init.d/rc?.d/). The program also takes care of the correct start and stop order for each runlevel by including the necessary numbers in the names of these links. If you prefer a graphical tool to create such links, use the runlevel editor provided by YaST, as described in Section 9.2.3, “Configuring System Services (Runlevel) with YaST”.

If a script already present in /etc/init.d/ should be integrated into the existing runlevel scheme, create the links in the runlevel directories right away with insserv or by enabling the corresponding service in the runlevel editor of YaST. Your changes are applied during the next reboot—the new service is started automatically.

Do not set these links manually. If something is wrong in the INFO block, problems will arise when insserv is run later for some other service. The manually added service will be removed with the next run of insserv for this script.

9.2.3. Configuring System Services (Runlevel) with YaST

After starting this YaST module with YaST+System+System Services (Runlevel), it displays an overview listing all the available services and the current status of each service (disabled or enabled). Decide whether to use the module in Simple Mode or in Expert Mode. The default Simple Mode should be sufficient for most purposes. The left column shows the name of the service, the center column indicates its current status and the right column gives a short description. For the selected service, a more detailed description is provided in the lower part of the window. To enable a service, select it in the table then select Enable. The same steps apply to disable a service.

For detailed control over the runlevels in which a service is started or stopped or to change the default runlevel, first select Expert Mode. The current default runlevel or initdefault (the runlevel into which the system boots by default) is displayed at the top. Normally, the default runlevel of a SUSE Linux Enterprise Server system is runlevel 5 (full multiuser mode with network and X). A suitable alternative might be runlevel 3 (full multiuser mode with network).

This YaST dialog allows the selection of one of the runlevels (as listed in Table 9.1, “Available Runlevels”) as the new default. Additionally, use the table in this window to enable or disable individual services and daemons. The table lists the services and daemons available, shows whether they are currently enabled on your system and, if so, for which runlevels. After selecting one of the rows with the mouse, click the check boxes representing the runlevels (B, 0, 1, 2, 3, 5, 6, and S) to define the runlevels in which the selected service or daemon should be running. Runlevel 4 is undefined to allow creation of a custom runlevel. A brief description of the currently selected service or daemon is provided below the table overview.

[Warning]Faulty Runlevel Settings May Damage Your System

Faulty runlevel settings may make your system unusable. Before applying your changes, make absolutely sure that you know their consequences.

Figure 9.1. System Services (Runlevel)

System Services (Runlevel)

With Start, Stop, or Refresh, decide whether a service should be activated. Refresh status checks the current status. Set or Reset lets you select whether to apply your changes to the system or to restore the settings that existed before starting the runlevel editor. Selecting OK saves the changed settings to disk.

9.3. System Configuration via /etc/sysconfig

The main configuration of SUSE Linux Enterprise Server is controlled by the configuration files in /etc/sysconfig. The individual files in /etc/sysconfig are only read by the scripts to which they are relevant. This ensures that network settings, for example, only need to be parsed by network-related scripts.

There are two ways to edit the system configuration. Either use the YaST sysconfig Editor or edit the configuration files manually.

9.3.1. Changing the System Configuration Using the YaST sysconfig Editor

The YaST sysconfig editor provides an easy-to-use front-end for system configuration. Without any knowledge of the actual location of the configuration variable you need to change, you can just use the built-in search function of this module, change the value of the configuration variable as needed and let YaST take care of applying these changes, updating configurations that depend on the values set in sysconfig and restarting services.

[Warning]Modifying /etc/sysconfig/* Files Can Damage Your Installation

Do not modify the /etc/sysconfig files if you lack previous experience and knowledge. It can do considerable damage to your system. The files in /etc/sysconfig include a short comment for each variable to explain what effect they actually have.

Figure 9.2. System Configuration Using the sysconfig Editor

System Configuration Using the sysconfig Editor

The YaST sysconfig dialog is split into three parts. The left part of the dialog shows a tree view of all configurable variables. When you select a variable, the right part displays both the current selection and the current setting of this variable. Below, a third window displays a short description of the variable's purpose, possible values, the default value and the actual configuration file from which this variable originates. The dialog also provides information about which configuration script is executed after changing the variable and which new service is started as a result of the change. YaST prompts you to confirm your changes and informs you which scripts will be executed after you leave the dialog by selecting Finish. Also select the services and scripts to skip for now, so they are started later. YaST applies all changes automatically and restarts any services involved for your changes to take an effect.

9.3.2. Changing the System Configuration Manually

To manually change the system configuration, proceed as follows

  1. Become root.

  2. Bring the system into single user mode (runlevel 1) with telinit 1.

  3. Change the configuration files as needed with an editor of your choice.

    If you do not use YaST to change the configuration files in /etc/sysconfig, make sure that empty variable values are represented by two quotation marks (KEYTABLE="") and that values with blanks in them are enclosed in quotation marks. Values consisting of one word only do not need to be quoted.

  4. Execute SuSEconfig to make sure that the changes take effect.

  5. Bring your system back to the previous runlevel with a command like telinit default_runlevel. Replace default_runlevel with the default runlevel of the system. Choose 5 if you want to return to full multiuser with network and X or choose 3 if you prefer to work in full multiuser with network.

This procedure is mainly relevant when changing systemwide settings, such as the network configuration. Small changes should not require going into single user mode, but you may still do so to make absolutely sure that all the programs concerned are correctly restarted.

[Tip]Configuring Automated System Configuration

To disable the automated system configuration by SuSEconfig, set the variable ENABLE_SUSECONFIG in /etc/sysconfig/suseconfig to no. Do not disable SuSEconfig if you want to use the SUSE installation support. It is also possible to disable the autoconfiguration partially.

Chapter 10. The Boot Loader GRUB

Abstract

This chapter describes how to configure GRUB (Grand Unified Bootloader), the boot loader used in SUSE® Linux Enterprise Server. A special YaST module is available for configuring all settings. If you are not familiar with the subject of booting in Linux, read the following sections to acquire some background information. This chapter also describes some of the problems frequently encountered when booting with GRUB and their solutions.

[Note]No GRUB on machines using UEFI

GRUB will routinely be installed on machines equipped with a traditional BIOS and on UEFI (Unified Extensible Firmware Interface) machines using a Compatibility Support Module (CSM). On UEFI machines without enabled CSM, eLILO will automatically be installed (provided DVD1 booted successfully). Refer to the eLILO documentation at /usr/share/doc/packages/elilo/ on your system for details.

This chapter focuses on boot management and the configuration of the boot loader GRUB. The boot procedure as a whole is outlined in Chapter 9, Booting and Configuring a Linux System. A boot loader represents the interface between the machine (BIOS) and the operating system (SUSE Linux Enterprise Server). The configuration of the boot loader directly impacts the start of the operating system.

The following terms appear frequently in this chapter and might need some explanation:

MBR (Master Boot Record)

The structure of the MBR is defined by an operating system–independent convention. The first 446 bytes are reserved for the program code. They typically hold part of a boot loader program or an operating system selector. The next 64 bytes provide space for a partition table of up to four entries. The partition table contains information about the partitioning of the hard disk and the file system types. The operating system needs this table for handling the hard disk. With conventional generic code in the MBR, exactly one partition must be marked active. The last two bytes of the MBR must contain a static magic number (AA55). An MBR containing a different value is regarded as invalid by some BIOSes, so is not considered for booting.

Boot Sectors

Boot sectors are the first sectors of hard disk partitions with the exception of the extended partition, which merely serves as a container for other partitions. These boot sectors have 512 bytes of space for code used to boot an operating system installed in the respective partition. This applies to boot sectors of formatted DOS, Windows, and OS/2 partitions, which also contain some basic important data of the file system. In contrast, the boot sectors of Linux partitions are initially empty after setting up a file system other than XFS. Therefore, a Linux partition is not bootable by itself, even if it contains a kernel and a valid root file system. A boot sector with valid code for booting the system has the same magic number as the MBR in its last two bytes (AA55).

10.1. Booting with GRUB

GRUB comprises two stages. Stage 1 consists of 512 bytes and its only task is to load the second stage of the boot loader. Subsequently, stage 2 is loaded. This stage contains the main part of the boot loader.

In some configurations, an intermediate stage 1.5 can be used, which locates and loads stage 2 from an appropriate file system. If possible, this method is chosen by default on installation or when initially setting up GRUB with YaST.

Stage 2 is able to access many file systems. Currently, ext2, ext3, ReiserFS, Minix, and the DOS FAT file system used by Windows are supported. To a certain extent, XFS, and UFS and FFS used by BSD systems are also supported. Since version 0.95 GRUB is also able to boot from a CD or DVD containing an ISO 9660 standard file system pursuant to the El Torito specification. Even before the system is booted, GRUB can access file systems of supported BIOS disk devices (floppy disks or hard disks, CD drives and DVD drives detected by the BIOS). Therefore, changes to the GRUB configuration file (menu.lst) do not require a new installation of the boot manager. When the system is booted, GRUB reloads the menu file with the valid paths and partition data of the kernel or the initial RAM disk (initrd) and locates these files.

The actual configuration of GRUB is based on four files that are described below:

/boot/grub/menu.lst

This file contains all information about partitions or operating systems that can be booted with GRUB. Without this information, the GRUB command line prompts the user for how to proceed (see Section 10.1.1.3, “Editing Menu Entries during the Boot Procedure” for details).

/boot/grub/device.map

This file translates device names from the GRUB and BIOS notation to Linux device names.

/etc/grub.conf

This file contains the commands, parameters and options the GRUB shell needs for installing the boot loader correctly.

/etc/sysconfig/bootloader

This file is read by the perl-bootloader library which is used when configuring the boot loader with YaST and every time a new kernel is installed. It contains configuration options (such as kernel parameters) that will be added by default to the boot loader configuration file.

GRUB can be controlled in various ways. Boot entries from an existing configuration can be selected from the graphical menu (splash screen). The configuration is loaded from the file menu.lst.

In GRUB, all boot parameters can be changed prior to booting. For example, errors made when editing the menu file can be corrected in this way. Boot commands can also be entered interactively at a kind of input prompt. For details, see Section 10.1.1.3, “Editing Menu Entries during the Boot Procedure”. GRUB offers the possibility of determining the location of the kernel and the initrd prior to booting. In this way, you can even boot an installed operating system for which no entry exists in the boot loader configuration.

GRUB actually exists in two versions: as a boot loader and as a normal Linux program in /usr/sbin/grub. The latter is referred to as the GRUB shell. It provides an emulation of GRUB in the installed system and can be used to install GRUB or test new settings before applying them. The functionality to install GRUB as the boot loader on a hard disk or floppy disk is integrated in GRUB in the form of the command setup. This is available in the GRUB shell when Linux is loaded.

10.1.1. The File /boot/grub/menu.lst

The graphical splash screen with the boot menu is based on the GRUB configuration file /boot/grub/menu.lst, which contains all information about all partitions or operating systems that can be booted by the menu.

Every time the system is booted, GRUB loads the menu file from the file system. For this reason, GRUB does not need to be reinstalled after every change to the file. Use the YaST boot loader to modify the GRUB configuration as described in Section 10.2, “Configuring the Boot Loader with YaST”.

The menu file contains commands. The syntax is very simple. Every line contains a command followed by optional parameters separated by spaces like in the shell. For historical reasons, some commands permit an = in front of the first parameter. Comments are introduced by a hash (#).

To identify the menu items in the menu overview, set a title for every entry. The text (including any spaces) following the keyword title is displayed as a selectable option in the menu. All commands up to the next title are executed when this menu item is selected.

The simplest case is the redirection to boot loaders of other operating systems. The command is chainloader and the argument is usually the boot block of another partition, in GRUB block notation. For example:

chainloader (hd0,3)+1

The device names in GRUB are explained in Section 10.1.1.1, “Naming Conventions for Hard Disks and Partitions”. This example specifies the first block of the fourth partition of the first hard disk.

Use the command kernel to specify a kernel image. The first argument is the path to the kernel image in a partition. The other arguments are passed to the kernel on its command line.

If the kernel does not have built-in drivers for access to the root partition or a recent Linux system with advanced hotplug features is used, initrd must be specified with a separate GRUB command whose only argument is the path to the initrd file. Because the loading address of the initrd is written into the loaded kernel image, the command initrd must follow after the kernel command.

The command root simplifies the specification of kernel and initrd files. The only argument of root is a device or a partition. This device is used for all kernel, initrd, or other file paths for which no device is explicitly specified until the next root command.

The boot command is implied at the end of every menu entry, so it does not need to be written into the menu file. However, if you use GRUB interactively for booting, you must enter the boot command at the end. The command itself has no arguments. It merely boots the loaded kernel image or the specified chain loader.

After writing all menu entries, define one of them as the default entry. Otherwise, the first one (entry 0) is used. You can also specify a time-out in seconds after which the default entry should boot. timeout and default usually precede the menu entries. An example file is described in Section 10.1.1.2, “An Example Menu File”.

10.1.1.1. Naming Conventions for Hard Disks and Partitions

The naming convention GRUB uses for hard disks and partitions differ from that used for normal Linux devices. It more closely resembles the simple disk enumeration the BIOS does and the syntax is similar to that used in some BSD derivatives. In GRUB, the numbering of the partitions start with zero. This means that (hd0,0) is the first partition of the first hard disk. On a common desktop machine with a hard disk connected as primary master, the corresponding Linux device name is /dev/sda1.

The four possible primary partitions are assigned the partition numbers 0 to 3. The logical partitions are numbered from 4:

(hd0,0)   first primary partition of the first hard disk
(hd0,1)   second primary partition
(hd0,2)   third primary partition
(hd0,3)   fourth primary partition (usually an extended partition)
(hd0,4)   first logical partition
(hd0,5)   second logical partition

Being dependent on BIOS devices, GRUB does not distinguish between PATA (IDE), SATA, SCSI, and hardware RAID devices. All hard disks recognized by the BIOS or other controllers are numbered according to the boot sequence preset in the BIOS.

Unfortunately, it is often not possible to map the Linux device names to BIOS device names exactly. It generates this mapping with the help of an algorithm and saves it to the file device.map, which can be edited if necessary. Information about the file device.map is available in Section 10.1.2, “The File device.map”.

A complete GRUB path consists of a device name written in parentheses and the path to the file in the file system in the specified partition. The path begins with a slash. For example, the bootable kernel could be specified as follows on a system with a single PATA (IDE) hard disk containing Linux in its first partition:

(hd0,0)/boot/vmlinuz

10.1.1.2. An Example Menu File

The following example shows the structure of a GRUB menu file. The example installation has a Linux boot partition under /dev/sda5, a root partition under /dev/sda7 and a Windows installation under /dev/sda1.

gfxmenu (hd0,4)/boot/message1
color white/blue black/light-gray2
default 03
timeout 84

title linux5
   root (hd0,4)
   kernel /boot/vmlinuz root=/dev/sda7 vga=791 resume=/dev/sda9
   initrd /boot/initrd

title windows6
   rootnoverify (hd0,0)
   chainloader +1

title floppy7
   rootnoverify (hd0,0)
   chainloader (fd0)+1

title failsafe8
   root (hd0,4)
   kernel /boot/vmlinuz.shipped root=/dev/sda7 ide=nodma \
   apm=off acpi=off vga=normal nosmp maxcpus=0 3 noresume
   initrd /boot/initrd.shipped

The first block defines the configuration of the splash screen:

1

The background image message is located in the /boot directory of the /dev/sda5 partition.

2

Color scheme: white (foreground), blue (background), black (selection) and light gray (background of the selection). The color scheme has no effect on the splash screen, only on the customizable GRUB menu that you can access by exiting the splash screen with Esc.

3

The first (0) menu entry title linux is booted by default.

4

After eight seconds without any user input, GRUB automatically boots the default entry. To deactivate automatic boot, delete the timeout line. If you set timeout 0, GRUB boots the default entry immediately.

The second and largest block lists the various bootable operating systems. The sections for the individual operating systems are introduced by title.

5

The first entry (title linux) is responsible for booting SUSE Linux Enterprise Server. The kernel (vmlinuz) is located in the first logical partition (the boot partition) of the first hard disk. Kernel parameters, such as the root partition and VGA mode, are appended here. The root partition is specified according to the Linux naming convention (/dev/sda7/) because this information is read by the kernel and has nothing to do with GRUB. The initrd is also located in the first logical partition of the first hard disk.

6

The second entry is responsible for loading Windows. Windows is booted from the first partition of the first hard disk (hd0,0). The command chainloader +1 causes GRUB to read and execute the first sector of the specified partition.

7

The next entry enables booting from floppy disk without modifying the BIOS settings.

8

The boot option failsafe starts Linux with a selection of kernel parameters that enables Linux to boot even on problematic systems.

The menu file can be changed whenever necessary. GRUB then uses the modified settings during the next boot. Edit the file permanently using YaST or an editor of your choice. Alternatively, make temporary changes interactively using the edit function of GRUB. See Section 10.1.1.3, “Editing Menu Entries during the Boot Procedure”.

10.1.1.3. Editing Menu Entries during the Boot Procedure

In the graphical boot menu, select the operating system to boot with the arrow keys. If you select a Linux system, you can enter additional boot parameters at the boot prompt. To edit individual menu entries directly, press Esc to exit the splash screen and get to the GRUB text-based menu then press E. Changes made in this way only apply to the current boot and are not adopted permanently.

[Important]Keyboard Layout during the Boot Procedure

The US keyboard layout is the only one available when booting. See Figure 35.3, “US Keyboard Layout”.

Editing menu entries facilitates the repair of a defective system that can no longer be booted, because the faulty configuration file of the boot loader can be circumvented by manually entering parameters. Manually entering parameters during the boot procedure is also useful for testing new settings without impairing the native system.

After activating the editing mode, use the arrow keys to select the menu entry of the configuration to edit. To make the configuration editable, press E again. In this way, edit incorrect partitions or path specifications before they have a negative effect on the boot process. Press Enter to exit the editing mode and return to the menu. Then press B to boot this entry. Further possible actions are displayed in the help text at the bottom.

To enter changed boot options permanently and pass them to the kernel, open the file menu.lst as the user root and append the respective kernel parameters to the existing line, separated by spaces:

title linux
   root(hd0,0)
     kernel /vmlinuz root=/dev/sda3 additional parameter
   initrd /initrd

GRUB automatically adopts the new parameters the next time the system is booted. Alternatively, this change can also be made with the YaST boot loader module. Append the new parameters to the existing line, separated by spaces.

10.1.2. The File device.map

The file device.map maps GRUB and BIOS device names to Linux device names. In a mixed system containing PATA (IDE) and SCSI hard disks, GRUB must try to determine the boot sequence by a special procedure, because GRUB may not have access to the BIOS information on the boot sequence. GRUB saves the result of this analysis in the file /boot/grub/device.map. Example device.map files for a system on which the boot sequence in the BIOS is set to PATA before SCSI could look as follows:

(fd0)  /dev/fd0
(hd0)  /dev/sda
(hd1)  /dev/sdb

or

(fd0)  /dev/fd0
(hd0)  /dev/disk-by-id/DISK1 ID
(hd1)  /dev/disk-by-id/DISK2 ID

Because the order of PATA (IDE), SCSI and other hard disks depends on various factors and Linux is not able to identify the mapping, the sequence in the file device.map can be set manually. If you encounter problems when booting, check if the sequence in this file corresponds to the sequence in the BIOS and use the GRUB prompt to modify it temporarily, if necessary. After the Linux system has booted, the file device.map can be edited permanently with the YaST boot loader module or an editor of your choice.

[Note]Maximum Number of Hard Disks

To address a hard disk, GRUB uses BIOS services. This is done via the software interrupt Int13h. Since Int13h is limited to handling a maximum number of eight disks, GRUB can only boot from the disks handled by Int13h, even if there are more disks present (which is often the case on multipath systems). The device.map file created during the installation will therefore only contain a maximum number of the eight disks handled by Int13h.

After manually changing device.map, execute the following command to reinstall GRUB. This command causes the file device.map to be reloaded and the commands listed in grub.conf to be executed:

grub --batch < /etc/grub.conf

10.1.3. The File /etc/grub.conf

The third important GRUB configuration file after menu.lst and device.map is /etc/grub.conf. This file contains the commands, parameters and options the GRUB shell needs for installing the boot loader correctly:

setup --stage2=/boot/grub/stage2 --force-lba (hd0,1) (hd0,1)
   quit

This command tells GRUB to automatically install the boot loader to the second partition on the first hard disk (hd0,1) using the boot images located on the same partition. The --stage2=/boot/grub/stage2 parameter is needed to install the stage2 image from a mounted file system. Some BIOSes have a faulty LBA support implementation, --force-lba provides a solution to ignore them.

10.1.4. The File /etc/sysconfig/bootloader

This configuration file is only used when configuring the boot loader with YaST and every time a new kernel is installed. It is evaluated by the perl-bootloader library which modifies the boot loader configuration file (for example /boot/grub/menu.lst for GRUB) accordingly. /etc/sysconfig/bootloader is not a GRUB specific configuration file - the values are applied to any boot loader installed on SUSE Linux Enterprise Server.

[Note]Boot loader Configuration after a Kernel Update

Every time a new kernel is installed, the perl-bootloader writes a new boot loader configuration file (for example /boot/grub/menu.lst for GRUB) using the defaults specified in /etc/sysconfig/bootloader. If you are using a customized set of kernel parameters, make sure to adjust the relevant defaults in /etc/sysconfig/bootloader according to your needs.

LOADER_TYPE

Specifies the boot loader installed on the system (e.g. GRUB or LILO). Do not modify—use YaST to change the boot loader as described in Procedure 10.6, “Changing the Boot Loader Type”.

DEFAULT_VGA / FAILSAFE_VGA / XEN_VGA

Screen resolution and color depth of the framebuffer used during booting are configured with the kernel parameter vga. These values define which resolution and color depth to use for the default boot entry, the failsafe and the XEN entry. The following values are valid:

Table 10.1. Screen Resolution and Color Depth Reference

640x480

800x600

1024x768

1280x1024

1600x1200

8bit

0x301

0x303

0x305

0x307

0x31C

15bit

0x310

0x313

0x316

0x319

0x31D

16bit

0x311

0x314

0x317

0x31A

0x31E

24bit

0x312

0x315

0x318

0x31B

0x31F


DEFAULT_APPEND / FAILSAFE_APPEND / XEN_KERNEL_APPEND

Kernel parameters (other than vga) that are automatically appended to the default, failsafe and XEN boot entries in the boot loader configuration file.

CYCLE_DETECTION / CYCLE_NEXT_ENTRY

Configure whether to use boot cycle detection and if so, which alternative entry from /boot/grub/menu.lst to boot in case of a reboot cycle (e.g. Failsafe). See /usr/share/doc/packages/bootcycle/README for detailed information.

10.1.5. Setting a Boot Password

Even before the operating system is booted, GRUB enables access to file systems. Users without root permissions can access files in your Linux system to which they have no access once the system is booted. To block this kind of access or to prevent users from booting certain operating systems, set a boot password.

[Important]Boot Password and Splash Screen

If you use a boot password for GRUB, the usual splash screen is not displayed.

As the user root, proceed as follows to set a boot password:

  1. At the root prompt, encrypt the password using grub-md5-crypt:

    # grub-md5-crypt
    Password: ****
    Retype password: ****
    Encrypted: $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/
  2. Paste the encrypted string into the global section of the file menu.lst:

    gfxmenu (hd0,4)/message
    color white/blue black/light-gray
    default 0
    timeout 8
    password --md5 $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/

    Now GRUB commands can only be executed at the boot prompt after pressing P and entering the password. However, users can still boot all operating systems from the boot menu.

  3. To prevent one or several operating systems from being booted from the boot menu, add the entry lock to every section in menu.lst that should not be bootable without entering a password. For example:

    title linux
       kernel (hd0,4)/vmlinuz root=/dev/sda7 vga=791
       initrd (hd0,4)/initrd
       lock

    After rebooting the system and selecting the Linux entry from the boot menu, the following error message is displayed:

    Error 32: Must be authenticated

    Press Enter to enter the menu. Then press P to get a password prompt. After entering the password and pressing Enter, the selected operating system (Linux in this case) should boot.

10.2. Configuring the Boot Loader with YaST

The easiest way to configure the boot loader in your SUSE Linux Enterprise Server system is to use the YaST module. In the YaST Control Center, select System+Boot Loader. As in Figure 10.1, “Boot Loader Settings”, this shows the current boot loader configuration of your system and allows you to make changes.

Figure 10.1. Boot Loader Settings

Boot Loader Settings

Use the Section Management tab to edit, change and delete boot loader sections for the individual operating systems. To add an option, click Add. To change the value of an existing option, select it with the mouse and click Edit. To remove an existing entry, select it and click Delete. If you are not familiar with boot loader options, read Section 10.1, “Booting with GRUB” first.

Use the Boot Loader Installation tab to view and change settings related to type, location and advanced loader settings.

Click Other to access advanced configuration options. The build-in editor lets you change the GRUB configuration files. For details, see Section 10.1, “Booting with GRUB”. You can also delete the existing configuration and Start from Scratch or let YaST Propose a New Configuration. It is also possible to write the configuration to disk or reread the configuration from the disk. To restore the original Master Boot Record (MBR) that was saved during the installation, choose Restore MBR of Hard Disk.

10.2.1. Adjusting the Default Boot Entry

To change the system that is booted by default, proceed as follows:

Procedure 10.1. Setting the Default System

  1. Open the Section Management tab.

  2. Select the desired entry from the list.

  3. Click Set as Default.

  4. Click OK to activate these changes.

10.2.2. Modifying the Boot Loader Location

To modify the location of the boot loader, follow these steps:

Procedure 10.2. Changing the Boot Loader Location

  1. Select the Boot Loader Installation tab and then choose one of the following options for Boot Loader Location:

    Boot from Master Boot Record

    This installs the boot loader in the MBR of the first disk (according to the boot sequence preset in the BIOS).

    Boot from Root Partition

    This installs the boot loader in the boot sector of the / partition (this is the default).

    Boot from Boot Partition

    This installs the boot loader in the boot sector of the /boot partition.

    Boot from Extended Partition

    This installs the boot loader in the extended partition container.

    Custom Boot Partition

    Use this option to specify the location of the boot loader manually.

  2. Click OK to apply your changes.

10.2.3. Changing the Boot Loader Time-Out

The boot loader does not boot the default system immediately. During the time-out, you can select the system to boot or write some kernel parameters. To set the boot loader time-out, proceed as follows:

Procedure 10.3. Changing the Boot Loader Time-Out

  1. Open the Boot Loader Installation tab.

  2. Click Boot Loader Options.

  3. Change the value of Time-Out in Seconds by typing in a new value and clicking the appropriate arrow key with your mouse, or by using the arrow keys on the keyboard.

  4. Click OK twice to save the changes.

[Warning]Timeout of 0 Seconds

When setting the timeout to 0 seconds, you will not be able to access GRUB during boot time. When having set the default boot option to a non-Linux operation system at the same time, this effectively disables access to the Linux system.

10.2.4. Setting a Boot Password

Using this YaST module, you can also set a password to protect booting. This gives you an additional level of security.

Procedure 10.4. Setting a Boot Loader Password

  1. Open the Boot Loader Installation tab.

  2. Click Boot Loader Options.

  3. Activate the Protect Boot Loader with Password option with a click and type in your Password twice.

  4. Click OK twice to save the changes.

10.2.5. Adjusting the Disk Order

If your computer has more than one hard disk, you can specify the boot sequence of the disks to match the BIOS setup of the machine (see Section 10.1.2, “The File device.map”). To do so, proceed as follows:

Procedure 10.5. Setting the Disk Order

  1. Open the Boot Loader Installation tab.

  2. Click Boot Loader Installation Details.

  3. If more than one disk is listed, select a disk and click Up or Down to reorder the displayed disks.

  4. Click OK two times to save the changes.

10.2.6. Configuring Advanced Options

Advanced boot options can be configured via Boot Loader Installation+Boot Loader Options. Normally, it should not be necessary to change the default settings.

Set Active Flag in Partition Table for Boot Partition

Activates the partition that contains the boot loader. Some legacy operating systems (such as Windows 98) can only boot from an active partition.

Write Generic Boot Code to MBR

Replaces the current MBR with generic, operating system independent code.

Debugging Flag

Sets GRUB in debug mode where it displays messages to show disk activity.

Hide Boot Menu

Hides the boot menu and boots the default entry.

[Warning]

When hiding the boot menu, you will not be able to access GRUB during boot time. When having set the default boot option to a non-Linux operation system at the same time, this effectively disables access to the Linux system.

Use Trusted GRUB

Starts the Trusted GRUB which supports trusted computing functionality.

Graphical Menu File

Path to the graphics file used when displaying the boot screen.

Serial Connection Parameters

If your machine is controlled via a serial console, you can specify which COM port to use at which speed. Also set Terminal Definition to serial. See info grub or http://www.gnu.org/software/grub/manual/grub.html for details.

Use Serial Console

If your machine is controlled via a serial console, activate this option and specify which COM port to use at which speed. See info grub or http://www.gnu.org/software/grub/manual/grub.html#Serial-terminal

10.2.7. Changing Boot Loader Type

Set the boot loader type in Boot Loader Installation. The default boot loader in SUSE Linux Enterprise Server is GRUB. To use LILO or ELILO, proceed as follows:

[Warning]LILO is unsupported

Using LILO is not recommended—it is unsupported on SUSE Linux Enterprise Server. Only use it in special cases.

Procedure 10.6. Changing the Boot Loader Type

  1. Select the Boot Loader Installation tab.

  2. For Boot Loader, select LILO.

  3. In the dialog box that opens, select one of the following actions:

    Propose New Configuration

    Have YaST propose a new configuration.

    Convert Current Configuration

    Have YaST convert the current configuration. When converting the configuration, some settings may be lost.

    Start New Configuration from Scratch

    Write a custom configuration. This action is not available during the installation of SUSE Linux Enterprise Server.

    Read Configuration Saved on Disk

    Load your own /etc/lilo.conf. This action is not available during the installation of SUSE Linux Enterprise Server.

  4. Click OK two times to save the changes.

During the conversion, the old GRUB configuration is saved to the disk. To use it, simply change the boot loader type back to GRUB and choose Restore Configuration Saved before Conversion. This action is available only on an installed system.

[Note]Custom Boot Loader

To use a boot loader other than GRUB or LILO, select Do Not Install Any Boot Loader. Read the documentation of your boot loader carefully before choosing this option.

10.3. Uninstalling the Linux Boot Loader

YaST can be used to uninstall the Linux boot loader and restore the MBR to the state it had prior to the installation of Linux. During the installation, YaST automatically creates a backup copy of the original MBR and restores it upon request.

To uninstall GRUB, start YaST and click System+Boot Loader to start the boot loader module. Select Other+Restore MBR of Hard Disk and confirm with Yes, Rewrite.

10.4. Creating Boot CDs

If problems occur while booting your system using a boot manager or if the boot manager cannot be installed on your hard disk disk, it is also possible to create a bootable CD with all the necessary start-up files for Linux. This requires a CD writer be installed in your system.

Creating a bootable CD-ROM with GRUB merely requires a special form of stage2 called stage2_eltorito and, optionally, a customized menu.lst. The classic files stage1 and stage2 are not required.

Procedure 10.7. Creating Boot CDs

  1. Change into a directory in which to create the ISO image, for example: cd /tmp

  2. Create a subdirectory for GRUB and change into the newly created iso directory:

    mkdir -p iso/boot/grub && cd iso
  3. Copy the kernel, the files stage2_eltorito, initrd, menu.lst and message to iso/boot/:

    cp /boot/vmlinuz boot/
    cp /boot/initrd boot/
    cp /boot/message boot/
    cp /usr/lib/grub/stage2_eltorito boot/grub
    cp /boot/grub/menu.lst boot/grub
  4. Replace the root (hdx, y) entries with root (cd) to point to the CD_ROM device. You may also need to adjust the paths to the message file, the kernel and the initrd—they need to point to /boot/message, /boot/vmlinuz and /boot/initrd, respectively. After having made the adjustments, menu.lst should look similar to the following example:

    timeout 8
    default 0
    gfxmenu (cd)/boot/message
    
    title Linux
       root (cd)
       kernel /boot/vmlinuz root=/dev/sda5 vga=794 resume=/dev/sda1 \
       splash=verbose showopts
       initrd /boot/initrd

    Use splash=silent instead of splash=verbose to prevent the boot messages from appearing during the boot procedure.

  5. Create the ISO image with the following command:

    genisoimage -R -b boot/grub/stage2_eltorito -no-emul-boot \
    -boot-load-size 4 -boot-info-table -iso-level 2 -input-charset utf-8 \
    -o grub.iso /tmp/iso
  6. Write the resulting file grub.iso to a CD using your preferred utility. Do not burn the ISO image as a data file, but use the option for burning a CD image in your burning utility.

10.5. The Graphical SUSE Screen

The graphical SUSE screen is displayed on the first console if the option vga=value is used as a kernel parameter. If you install using YaST, this option is automatically activated in accordance with the selected resolution and the graphics card. There are three ways to disable the SUSE screen, if desired:

Disabling the SUSE Screen When Necessary

Enter the command echo 0 >/proc/splash on the command line to disable the graphical screen. To activate it again, enter echo 1 >/proc/splash.

Disabling the SUSE screen by default.

Add the kernel parameter splash=0 to your boot loader configuration. Chapter 10, The Boot Loader GRUB provides more information about this. However, if you prefer the text mode (the default in earlier versions) set vga=normal.

Completely Disabling the SUSE Screen

Compile a new kernel and disable the option Use splash screen instead of boot logo in framebuffer support. Disabling framebuffer support in the kernel automatically disables the splash screen, as well.

[Warning]No Support

SUSE cannot provide any support for your system if you run it with a custom kernel.

10.6. Troubleshooting

This section lists some of the problems frequently encountered when booting with GRUB and a short description of possible solutions. Some of the problems are covered in articles in the Knowledge base at http://www.suse.com/support. Use the search dialog to search for keywords like GRUB, boot and boot loader.

GRUB and XFS

XFS leaves no room for stage1 in the partition boot block. Therefore, do not specify an XFS partition as the location of the boot loader. This problem can be solved by creating a separate boot partition that is not formatted with XFS.

GRUB Reports GRUB Geom Error

GRUB checks the geometry of connected hard disks when the system is booted. Sometimes, the BIOS returns inconsistent information and GRUB reports a GRUB Geom Error. In this case, update the BIOS.

GRUB also returns this error message if Linux was installed on an additional hard disk that is not registered in the BIOS. stage1 of the boot loader is found and loaded correctly, but stage2 is not found. This problem can be remedied by registering the new hard disk in the BIOS.

System Containing Several Hard Disks Does Not Boot

During the installation, YaST may have incorrectly determined the boot sequence of the hard disks. For example, GRUB may regard the PATA (IDE) disk as hd0 and the SCSI disk as hd1, although the boot sequence in the BIOS is reversed (SCSI before PATA).

In this case, correct the hard disks during the boot process with the help of the GRUB command line. After the system has booted, edit device.map to apply the new mapping permanently. Then check the GRUB device names in the files /boot/grub/menu.lst and /boot/grub/device.map and reinstall the boot loader with the following command:

grub --batch < /etc/grub.conf
Booting Windows from the Second Hard Disk

Some operating systems, such as Windows, can only boot from the first hard disk. If such an operating system is installed on a hard disk other than the first hard disk, you can effect a logical change for the respective menu entry.

...
title windows
   map (hd0) (hd1)
   map (hd1) (hd0)
   chainloader(hd1,0)+1
...

In this example, Windows is started from the second hard disk. For this purpose, the logical order of the hard disks is changed with map. This change does not affect the logic within the GRUB menu file. Therefore, the second hard disk must be specified for chainloader.

10.7. For More Information

Extensive information about GRUB is available at http://www.gnu.org/software/grub/. Also refer to the grub info page. You can also search for the keyword GRUB in the Technical Information Search at http://www.novell.com/support to get information about special issues.

Chapter 11. UEFI (Unified Extensible Firmware Interface)

UEFI (Unified Extensible Firmware Interface) is the interface between the firmware that comes with the system hardware, all the hardware components of the system, and the operating system.

UEFI is becoming more and more available on PC systems and thus is replacing the traditional PC-BIOS. UEFI, for example, properly supports 64-bit systems and offers secure booting (Secure Boot, firmware version 2.3.1c or better required), which is one of its most important features. Last but not least, with UEFI a standard firmware will become available on all x86 platforms.

UEFI additionally offers the following advantages:

  • Booting from large disks (over 2 TiB) with a GUID Partition Table (GPT).

  • CPU-independent architecture and drivers.

  • Flexible pre-OS environment with network capabilities.

  • CSM (Compatibility Support Module) to support booting legacy operating systems via a PC-BIOS-like emulation.

For more information, see http://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface. The following sections are not meant as a general UEFI overview; these are just hints about how some features are implemented in SUSE Linux Enterprise.

11.1. Secure Boot

In the world of UEFI, securing the bootstrapping process means establishing a chain of trust. The platform is the root of this chain of trust; in the context of SUSE Linux Enterprise, the motherboard and the on-board firmware could be considered the platform. Or, put slightly differently, it is the hardware vendor, and the chain of trust flows from that hardware vendor to the component manufacturers, the OS vendors, etc.

The trust is expressed via public key cryptography. The hardware vendor puts a so-called Platform Key (PK) into the firmware, representing the root of trust. The trust relationship with operating system vendors and others is documented by signing their keys with the Platform Key.

Finally, security is established by requiring that no code will be executed by the firmware unless it has been signed by one of these trusted keys—be it an OS boot loader, some driver located in the flash memory of some PCI Express card or on disk, or be it an update of the firmware itself.

Essentially, if you want to use Secure Boot, you need to have your OS loader signed with a key trusted by the firmware, and you need the OS loader to verify that the kernel it loads can be trusted.

Key Exchange Keys (KEK) can be added to the UEFI key database. This way, you can use other certificates, as long as they are signed with the private part of the PK.

11.1.1. Implementation on SUSE Linux Enterprise

Microsoft’s Key Exchange Key (KEK) is installed by default.

[Note]GUID Partitioning Table (GPT) Required

The Secure Boot feature requires that a GUID Partitioning Table (GPT) replaces the old partitioning with a Master Boot Record (MBR).

If YaST detects EFI mode during the installation, it will try to create a GPT partition. UEFI expects to find the EFI programs on a FAT-formatted EFI System Partition (ESP).

Supporting UEFI Secure Boot essentially requires having a boot loader with a digital signature that the firmware recognizes as a trusted key. In order to be useful to SUSE Linux Enterprise customers, that key is trusted by the firmware a priori, without requiring any manual intervention.

There are two ways of getting there. One is to work with hardware vendors to have them endorse a SUSE key, which SUSE then signs the boot loader with. The other way is to go through Microsoft’s Windows Logo Certification program to have the boot loader certified and have Microsoft recognize the SUSE signing key (i.e., have it signed with their KEK). By now, SUSE got the loader signed by UEFI Signing Service (that's Microsoft in this case).

Figure 11.1. UEFI: Secure Boot Process

UEFI: Secure Boot Process

At the implementation layer, SUSE uses the shim loader—it is a smart solution that avoids legal issues, and simplifies the certification and signing step considerably. The shim loader’s job is to load a boot loader such as eLILO or GRUB2 and verify it; this boot loader in turn will load kernels signed by a SUSE key only. SUSE provides this functionality with SLE11 SP3 on fresh installations with UEFI Secure Boot enabled.

There are two types of trusted users:

  • First, those who hold the keys. The Platform Key (PK) allows almost everything. The Key Exchange Key (KEK) allows all a PK can except changing the PK.

  • Second, anyone with physical access to the machine. A user with physical access can reboot the machine, and configure UEFI.

UEFI offers two types of variables to fulfill the needs of those users:

  • The first is the so-called Authenticated Variables, which can be updated from both within the boot process (the so-called Boot Services Environment) and the running OS, but only when the new value of the variable is signed with the same key that the old value of the variable was signed with. And they can only be appended to or changed to a value with a higher serial number.

  • The second is the so-called Boot Services Only Variables. These variables are accessible to any code that runs during the boot process. After the boot process ends and before the OS starts, the boot loader must call the ExitBootServices call. After that, these variables are no longer accessible, and the OS cannot touch them.

The various UEFI key lists are of the first type, as this allows online updating, adding, and blacklisting of keys, drivers, and firmware fingerprints. It is the second type of variable, the Boot Services Only Variable, that helps to implement Secure Boot, in a matter that is both secure and open source friendly, and thus compatible with GPLv3.

SUSE starts with shim—a small and simple EFI boot loader—which was originally developed by Fedora. It is signed by a certificate signed by the SUSE KEK and a Microsoft-issued certificate, based on which KEKs are available in the UEFI key database on the system.

This allows shim to load and execute.

shim then goes on to verify that the boot loader it wants to load is trusted. In a default situation shim will use an independent SUSE certificate embedded in its body. In addition, shim will allow to enroll additional keys, overriding the default SUSE key. In the following, we call them Machine Owner Keys or MOKs for short.

Next the boot loader will verify and then boot the kernel, and the kernel will do the same on the modules.

11.1.2. MOK (Machine Owner Key)

If the user (machine owner) wants to replace any components of the boot process, Machine Owner Keys (MOKs) are to be used. The mokutils tool will help with signing components and managing MOKs.

The enrollment process begins with rebooting the machine and interrupting the boot process (e.g., pressing a key) when shim loads. shim will then go into enrollment mode, allowing the user to replace the default SUSE key with keys from a file on the boot partition. If the user chooses to do so, shim will then calculate a hash of that file and put the result in a Boot Services Only variable. This allows shim to detect any change of the file made outside of Boot Services and thus avoid tampering with the list of user-approved MOKs.

All of this happens during boot time—only verified code is executing now. Therefore, only a user present at the console can use the machine owner's set of keys. It cannot be malware or a hacker with remote access to the OS because hackers or malware can only change the file, but not the hash stored in the Boot Services Only variable.

The boot loader, once loaded and verified by shim, will call back to shim when it wants to verify the kernel—to avoid duplication of the verification code. Shim will use the same list of MOKs for this and tell the boot loader whether it can load the kernel.

This way, you can install your own kernel or boot loader. It is only necessary to install a new set of keys and authorize them by being physically present during the first reboot. Because MOKs are a list and not just a single MOK, you can make shim trust keys from several different vendors, allowing dual- and multi-boot from the boot loader.

11.1.3. Booting a Custom Kernel

The following is based on http://en.opensuse.org/openSUSE:UEFI#Booting_a_custom_kernel.

Secure Boot does not prevent you from using a self-compiled kernel. You just must sign it with your own certificate and make that certificate known to the firmware or MOK.

  1. Create a custom X.509 key and certificate used for signing:

    openssl req -new -x509 -newkey rsa:2048 -keyout key.asc \
      -out cert.pem -nodes -days 666 -subj "/CN=$USER/"

    For more information about creating certificates, see http://en.opensuse.org/openSUSE:UEFI_Image_File_Sign_Tools#Create_Your_Own_Certificate.

  2. Package the key and the certificate as a PKCS#12 structure:

    openssl pkcs12 -export -inkey key.asc -in cert.pem \
      -name kernel_cert -out cert.p12
  3. Generate an NSS database for use with pesign:

    certutil -d . -N
  4. Import the key and the certificate contained in PKCS#12 into the NSS database:

    pk12util -d . -i cert.p12
  5. Bless the kernel with the new signature using pesign:

    pesign -n . -c kernel_cert -i arch/x86/boot/bzImage \
      -o vmlinuz.signed -s
  6. List the signatures on the kernel image:

    pesign -n . -S -i vmlinuz.signed

    At that point, you can install the kernel in /boot as usual. Because the kernel now has a custom signature the certificate used for signing needs to be imported into the UEFI firmware or MOK.

  7. Convert the certificate to the DER format for import into the firmware or MOK:

    openssl x509 -in cert.pem -outform der -out cert.der
  8. Copy the certificate to the ESP for easier access:

    sudo cp cert.der /boot/efi/
  9. Use mokutil to launch the MOK list automatically.

    Alternatively, this is the procedure if you want to launch MOK manually:

    1. Reboot

    2. In the GRUB menu press the 'c' key.

    3. Type:

      chainloader $efibootdir/MokManager.efi
      boot
    4. Select Enroll key from disk.

    5. Navigate to the cert.der file and press Enter.

    6. Follow the instructions to enroll the key. Normally this should be pressing '0' and then 'y' to confirm.

      Alternatively, the firmware menu may provide ways to add a new key to the Signature Database.

11.1.4. Limitations

When booting in Secure Boot mode, the following restrictions apply:

  • Hybridified ISO images are not recognized as bootable on UEFI systems. Thus, UEFI booting from USB devices is not supported with SP3.

  • To ensure that Secure Boot cannot be easily circumvented, some kernel features are disabled when running under Secure Boot.

  • Bootloader, kernel, and kernel modules must be signed.

  • kexec and kdump are disabled.

  • Hibernation (suspend on disk) is disabled.

  • Access to /dev/kmem and /dev/mem is not possible, not even as root user.

  • Access to the I/O port is not possible, not even as root user. All X11 graphical drivers must use a kernel driver.

  • PCI BAR access through sysfs is not possible.

  • custom_method in ACPI is not available.

  • debugfs for asus-wmi module is not available.

  • acpi_rsdp parameter does not have any effect on the kernel.

11.2. For More Information

Chapter 12. Special System Features

Abstract

This chapter starts with information about various software packages, the virtual consoles and the keyboard layout. We talk about software components like bash, cron and logrotate, because they were changed or enhanced during the last release cycles. Even if they are small or considered of minor importance, users may want to change their default behavior, because these components are often closely coupled with the system. The chapter concludes with a section about language and country-specific settings (I18N and L10N).

12.1. Information about Special Software Packages

The programs bash, cron, logrotate, locate, ulimit and free are very important for system administrators and many users. Man pages and info pages are two useful sources of information about commands, but both are not always available. GNU Emacs is a popular and very configurable text editor.

12.1.1. The bash Package and /etc/profile

Bash is the default system shell. When used as a login shell, it reads several initialization files. Bash processes them in the order they appear in this list:

  1. /etc/profile

  2. ~/.profile

  3. /etc/bash.bashrc

  4. ~/.bashrc

Make custom settings in ~/.profile or ~/.bashrc. To ensure the correct processing of these files, it is necessary to copy the basic settings from /etc/skel/.profile or /etc/skel/.bashrc into the home directory of the user. It is recommended to copy the settings from /etc/skel after an update. Execute the following shell commands to prevent the loss of personal adjustments:

mv ~/.bashrc ~/.bashrc.old
cp /etc/skel/.bashrc ~/.bashrc
mv ~/.profile ~/.profile.old
cp /etc/skel/.profile ~/.profile

Then copy personal adjustments back from the *.old files.

12.1.2. The cron Package

If you want to run commands regularly and automatically in the background at predefined times, cron is the tool to use. cron is driven by specially formatted time tables. Some of them come with the system and users can write their own tables if needed.

The cron tables are located in /var/spool/cron/tabs. /etc/crontab serves as a systemwide cron table. Enter the username to run the command directly after the time table and before the command. In Example 12.1, “Entry in /etc/crontab”, root is entered. Package-specific tables, located in /etc/cron.d, have the same format. See the cron man page (man cron).

Example 12.1. Entry in /etc/crontab

1-59/5 * * * *   root   test -x /usr/sbin/atrun && /usr/sbin/atrun

You cannot edit /etc/crontab by calling the command crontab -e. This file must be loaded directly into an editor, then modified and saved.

A number of packages install shell scripts to the directories /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly and /etc/cron.monthly, whose execution is controlled by /usr/lib/cron/run-crons. /usr/lib/cron/run-crons is run every 15 minutes from the main table (/etc/crontab). This guarantees that processes that may have been neglected can be run at the proper time.

To run the hourly, daily or other periodic maintenance scripts at custom times, remove the time stamp files regularly using /etc/crontab entries (see Example 12.2, “/etc/crontab: Remove Time Stamp Files”, which removes the hourly one before every full hour, the daily one once a day at 2:14 a.m., etc.).

Example 12.2. /etc/crontab: Remove Time Stamp Files

59 *  * * *     root  rm -f /var/spool/cron/lastrun/cron.hourly
14 2  * * *     root  rm -f /var/spool/cron/lastrun/cron.daily
29 2  * * 6     root  rm -f /var/spool/cron/lastrun/cron.weekly
44 2  1 * *     root  rm -f /var/spool/cron/lastrun/cron.monthly

Or you can set DAILY_TIME in /etc/sysconfig/cron to the time at which cron.daily should start. The setting of MAX_NOT_RUN ensures that the daily tasks get triggered to run, even if the user did not turn on the computer at the specified DAILY_TIME for a longer period of time. The maximum value of MAX_NOT_RUN is 14 days.

The daily system maintenance jobs are distributed to various scripts for reasons of clarity. They are contained in the package aaa_base. /etc/cron.daily contains, for example, the components suse.de-backup-rpmdb, suse.de-clean-tmp or suse.de-cron-local.

12.1.3. Log Files: Package logrotate

There are a number of system services (daemons) that, along with the kernel itself, regularly record the system status and specific events onto log files. This way, the administrator can regularly check the status of the system at a certain point in time, recognize errors or faulty functions and troubleshoot them with pinpoint precision. These log files are normally stored in /var/log as specified by FHS and grow on a daily basis. The logrotate package helps control the growth of these files.

Configure logrotate with the file /etc/logrotate.conf. In particular, the include specification primarily configures the additional files to read. Programs that produce log files install individual configuration files in /etc/logrotate.d. For example, such files ship with the packages apache2 (/etc/logrotate.d/apache2) and syslogd (/etc/logrotate.d/syslog).

Example 12.3. Example for /etc/logrotate.conf

# see "man logrotate" for details
# rotate log files weekly
weekly

# keep 4 weeks worth of backlogs
rotate 4

# create new (empty) log files after rotating old ones
create

# uncomment this if you want your log files compressed
#compress

# RPM packages drop log rotation information into this directory
include /etc/logrotate.d

# no packages own lastlog or wtmp - we'll rotate them here
#/var/log/wtmp {
#    monthly
#    create 0664 root utmp
#    rotate 1
#}

# system-specific logs may be also be configured here.

logrotate is controlled through cron and is called daily by /etc/cron.daily/logrotate.

[Important]

The create option reads all settings made by the administrator in /etc/permissions*. Ensure that no conflicts arise from any personal modifications.

12.1.4. The locate Command

locate, a command for quickly finding files, is not included in the standard scope of installed software. If desired, install the package findutils-locate. The updatedb process is started automatically every night or about 15 minutes after booting the system.

12.1.5. The ulimit Command

With the ulimit (user limits) command, it is possible to set limits for the use of system resources and to have these displayed. ulimit is especially useful for limiting available memory for applications. With this, an application can be prevented from co-opting too much of the system resources and slowing or even hanging up the operating system.

ulimit can be used with various options. To limit memory usage, use the options listed in Table 12.1, “ulimit: Setting Resources for the User”.

Table 12.1. ulimit: Setting Resources for the User

-m

The maximum resident set size

-v

The maximum amount of virtual memory available to the shell

-s

The maximum size of the stack

-c

The maximum size of core files created

-a

All current limits are reported


Systemwide entries can be made in /etc/profile. There, enable creation of core files (needed by programmers for debugging). A normal user cannot increase the values specified in /etc/profile by the system administrator, but can make special entries in ~/.bashrc.

Example 12.4. ulimit: Settings in ~/.bashrc

# Limits maximum resident set size (physical memory):
ulimit -m 98304
 
# Limits of virtual memory:
ulimit -v 98304

Memory allocations must be specified in KB. For more detailed information, see man bash.

[Important]

Not all shells support ulimit directives. PAM (for instance, pam_limits) offers comprehensive adjustment possibilities if you depend on encompassing settings for these restrictions.

12.1.6. The free Command

The free command displays the total amount of free and used physical memory and swap space in the system, as well as the buffers and cache consumed by the kernel. The concept of available RAM dates back to before the days of unified memory management. The slogan free memory is bad memory applies well to Linux. As a result, Linux has always made the effort to balance out caches without actually allowing free or unused memory.

Basically, the kernel does not have direct knowledge of any applications or user data. Instead, it manages applications and user data in a page cache. If memory runs short, parts of it are written to the swap partition or to files, from which they can initially be read with the help of the mmap command (see man mmap).

The kernel also contains other caches, such as the slab cache, where the caches used for network access are stored. This may explain the differences between the counters in /proc/meminfo. Most, but not all, of them can be accessed via /proc/slabinfo.

However, if your goal is to find out how much RAM is currently being used, find this information in /proc/meminfo.

12.1.7. Man Pages and Info Pages

For some GNU applications (such as tar), the man pages are no longer maintained. For these commands, use the --help option to get a quick overview of the info pages, which provide more in-depth instructions. Info is GNU's hypertext system. Read an introduction to this system by entering info info. Info pages can be viewed with Emacs by entering emacs -f info or directly in a console with info. You can also use tkinfo, xinfo or the help system to view info pages.

12.1.8. Selecting Man Pages Using the man Command

To read a man page enter man man_page. If a man page with the same name exists in different sections, they will all be listed with the corresponding section numbers. Select the one to display. If you don't enter a section number within a few seconds, the first man page will be displayed.

If you want to change this to the default system behavior, set MAN_POSIXLY_CORRECT=1 in a shell initialization file such as ~/.bashrc.

12.1.9. Settings for GNU Emacs

GNU Emacs is a complex work environment. The following sections cover the configuration files processed when GNU Emacs is started. More information is available at http://www.gnu.org/software/emacs/.

On start-up, Emacs reads several files containing the settings of the user, system administrator and distributor for customization or preconfiguration. The initialization file ~/.emacs is installed to the home directories of the individual users from /etc/skel. .emacs, in turn, reads the file /etc/skel/.gnu-emacs. To customize the program, copy .gnu-emacs to the home directory (with cp /etc/skel/.gnu-emacs ~/.gnu-emacs) and make the desired settings there.

.gnu-emacs defines the file ~/.gnu-emacs-custom as custom-file. If users make settings with the customize options in Emacs, the settings are saved to ~/.gnu-emacs-custom.

With SUSE Linux Enterprise Server, the emacs package installs the file site-start.el in the directory /usr/share/emacs/site-lisp. The file site-start.el is loaded before the initialization file ~/.emacs. Among other things, site-start.el ensures that special configuration files distributed with Emacs add-on packages, such as psgml, are loaded automatically. Configuration files of this type are located in /usr/share/emacs/site-lisp, too, and always begin with suse-start-. The local system administrator can specify systemwide settings in default.el.

More information about these files is available in the Emacs info file under Init File: info:/emacs/InitFile. Information about how to disable the loading of these files (if necessary) is also provided at this location.

The components of Emacs are divided into several packages:

  • The base package emacs.

  • emacs-x11 (usually installed): the program with X11 support.

  • emacs-nox: the program without X11 support.

  • emacs-info: online documentation in info format.

  • emacs-el: the uncompiled library files in Emacs Lisp. These are not required at runtime.

  • Numerous add-on packages can be installed if needed: emacs-auctex (LaTeX), psgml (SGML and XML), gnuserv (client and server operation) and others.

12.2. Virtual Consoles

Linux is a multiuser and multitasking system. The advantages of these features can be appreciated even on a stand-alone PC system. In text mode, there are six virtual consoles available. Switch between them using Alt+F1 through Alt+F6. The seventh console is reserved for X and the tenth console shows kernel messages. More or fewer consoles can be assigned by modifying the file /etc/inittab.

To switch to a console from X without shutting it down, use Ctrl+Alt+F1 to Ctrl+Alt+F6. To return to X, press Alt+F7.

12.3. Keyboard Mapping

To standardize the keyboard mapping of programs, changes were made to the following files:

/etc/inputrc
/etc/X11/Xmodmap
/etc/skel/.emacs
/etc/skel/.gnu-emacs
/etc/skel/.vimrc
/etc/csh.cshrc
/etc/termcap
/usr/share/terminfo/x/xterm
/usr/share/X11/app-defaults/XTerm
/usr/share/emacs/VERSION/site-lisp/term/*.el

These changes only affect applications that use terminfo entries or whose configuration files are changed directly (vi, emacs, etc.). Applications not shipped with the system should be adapted to these defaults.

Under X, the compose key (multikey) can be enabled as explained in /etc/X11/Xmodmap.

Further settings are possible using the X Keyboard Extension (XKB). This extension is also used by the desktop environments GNOME (gswitchit) and KDE (kxkb).

[Tip]For More Information

Information about XKB is available in the documents listed in /usr/share/doc/packages/xkeyboard-config (part of the xkeyboard-config package).

12.4. Language and Country-Specific Settings

The system is, to a very large extent, internationalized and can be modified for local needs. Internationalization (I18N) allows specific localizations (L10N). The abbreviations I18N and L10N are derived from the first and last letters of the words and, in between, the number of letters omitted.

Settings are made with LC_ variables defined in the file /etc/sysconfig/language. This refers not only to native language support, but also to the categories Messages (Language), Character Set, Sort Order, Time and Date, Numbers and Money. Each of these categories can be defined directly with its own variable or indirectly with a master variable in the file language (see the locale man page).

RC_LC_MESSAGES, RC_LC_CTYPE, RC_LC_COLLATE, RC_LC_TIME, RC_LC_NUMERIC, RC_LC_MONETARY

These variables are passed to the shell without the RC_ prefix and represent the listed categories. The shell profiles concerned are listed below. The current setting can be shown with the command locale.

RC_LC_ALL

This variable, if set, overwrites the values of the variables already mentioned.

RC_LANG

If none of the previous variables are set, this is the fallback. By default, only RC_LANG is set. This makes it easier for users to enter their own values.

ROOT_USES_LANG

A yes or no variable. If set to no, root always works in the POSIX environment.

The variables can be set with the YaST sysconfig editor (see Section 9.3.1, “Changing the System Configuration Using the YaST sysconfig Editor”). The value of such a variable contains the language code, country code, encoding and modifier. The individual components are connected by special characters:

  LANG=<language>[[_<COUNTRY>].<Encoding>[@<Modifier>]]

12.4.1. Some Examples

You should always set the language and country codes together. Language settings follow the standard ISO 639 available at http://www.evertype.com/standards/iso639/iso639-en.html and http://www.loc.gov/standards/iso639-2/. Country codes are listed in ISO 3166, see http://en.wikipedia.org/wiki/ISO_3166.

It only makes sense to set values for which usable description files can be found in /usr/lib/locale. Additional description files can be created from the files in /usr/share/i18n using the command localedef. The description files are part of the glibc-i18ndata package. A description file for en_US.UTF-8 (for English and United States) can be created with:

localedef -i en_US -f UTF-8 en_US.UTF-8
LANG=en_US.UTF-8

This is the default setting if American English is selected during installation. If you selected another language, that language is enabled but still with UTF-8 as the character encoding.

LANG=en_US.ISO-8859-1

This sets the language to English, country to United States and the character set to ISO-8859-1. This character set does not support the Euro sign, but it can be useful sometimes for programs that have not been updated to support UTF-8. The string defining the charset (ISO-8859-1 in this case) is then evaluated by programs like Emacs.

LANG=en_IE@euro

The above example explicitly includes the Euro sign in a language setting. This setting is basically obsolete now, as UTF-8 also covers the Euro symbol. It is only useful if an application supports ISO-8859-15 and not UTF-8.

In former releases, it was necessary to run SuSEconfig after doing any changes to /etc/sysconfig/language. SuSEconfig then wrote the changes to /etc/SuSEconfig/profile and /etc/SuSEconfig/csh.login. Upon login, these files were read by /etc/profile (for the Bash) or by /etc/csh.login (for the tcsh) .

In recent releases, /etc/SuSEconfig/profile has been replaced with /etc/profile.d/lang.sh, and /etc/SuSEconfig/csh.login with /etc/profile.de/lang.csh. But if they exist, both legacy file are still read upon login.

The process chain is now as follows:

  • For the Bash: /etc/profile reads /etc/profile.d/lang.sh which, in turn, analyzes /etc/sysconfig/language.

  • For tcsh: At login, /etc/csh.login reads /etc/profile.d/lang.csh which, in turn, analyzes /etc/sysconfig/language.

This ensures that any changes to /etc/sysconfig/language are available at the next login to the respective shell, without having to run SuSEconfig first.

Users can override the system defaults by editing their ~/.bashrc accordingly. For instance, if you do not want to use the systemwide en_US for program messages, include LC_MESSAGES=es_ES so that messages are displayed in Spanish instead.

12.4.2. Locale Settings in ~/.i18n

If you are not satisfied with locale system defaults, change the settings in ~/.i18n according to the Bash scripting syntax. Entries in ~/.i18n override system defaults from /etc/sysconfig/language. Use the same variable names but without the RC_ namespace prefixes. For example, use LANG instead of RC_LANG:

LANG=cs_CZ.UTF-8
LC_COLLATE=C

12.4.3. Settings for Language Support

Files in the category Messages are, as a rule, only stored in the corresponding language directory (like en) to have a fallback. If you set LANG to en_US and the message file in /usr/share/locale/en_US/LC_MESSAGES does not exist, it falls back to /usr/share/locale/en/LC_MESSAGES.

A fallback chain can also be defined, for example, for Breton to French or for Galician to Spanish to Portuguese:

LANGUAGE="br_FR:fr_FR"

LANGUAGE="gl_ES:es_ES:pt_PT"

If desired, use the Norwegian variants Nynorsk and Bokmål instead (with additional fallback to no):

LANG="nn_NO"

LANGUAGE="nn_NO:nb_NO:no"

or

LANG="nb_NO"

LANGUAGE="nb_NO:nn_NO:no"

Note that in Norwegian, LC_TIME is also treated differently.

One problem that can arise is a separator used to delimit groups of digits not being recognized properly. This occurs if LANG is set to only a two-letter language code like de, but the definition file glibc uses is located in /usr/share/lib/de_DE/LC_NUMERIC. Thus LC_NUMERIC must be set to de_DE to make the separator definition visible to the system.

12.4.4. For More Information

Chapter 13. Printer Operation

SUSE® Linux Enterprise Server supports printing with many types of printers, including remote network printers. Printers can be configured manually or with YaST. For configuration instructions, refer to Section “Setting Up a Printer” (Chapter 8, Setting Up Hardware Components with YaST, ↑Deployment Guide). Both graphical and command line utilities are available for starting and managing print jobs. If your printer does not work as expected, refer to Section 13.7, “Troubleshooting”.

CUPS (Common Unix Printing System) is the standard print system in SUSE Linux Enterprise Server.

Printers can be distinguished by interface, such as USB or network, and printer language. When buying a printer, make sure that the printer has an interface (like USB or parallel port) that is available on your hardware and a suitable printer language. Printers can be categorized on the basis of the following three classes of printer languages:

PostScript Printers

PostScript is the printer language in which most print jobs in Linux and Unix are generated and processed by the internal print system. If PostScript documents can be processed directly by the printer and do not need to be converted in additional stages in the print system, the number of potential error sources is reduced.

Standard Printers (Languages Like PCL and ESC/P)

Although these printer languages are quite old, they are still undergoing expansion to address new features in printers. In the case of known printer languages, the print system can convert PostScript jobs to the respective printer language with the help of Ghostscript. This processing stage is referred to as interpreting. The best-known languages are PCL (which is mostly used by HP printers and their clones) and ESC/P (which is used by Epson printers). These printer languages are usually supported by Linux and produce an adequate print result. Linux may not be able to address some special printer functions. Except for HP developing HPLIP (HP Linux Imaging and Printing), there are currently no printer manufacturers who develop Linux drivers and make them available to Linux distributors under an open source license.

Proprietary Printers (Also Called GDI Printers)

These printers do not support any of the common printer languages. They use their own undocumented printer languages, which are subject to change when a new edition of a model is released. Usually only Windows drivers are available for these printers. See Section 13.7.1, “Printers without Standard Printer Language Support” for more information.

Before you buy a new printer, refer to the following sources to check how well the printer you intend to buy is supported:

http://www.linuxfoundation.org/OpenPrinting/

The OpenPrinting home page with the printer database. The database shows the latest Linux support status. However, a Linux distribution can only integrate the drivers available at production time. Accordingly, a printer currently rated as perfectly supported may not have had this status when the latest SUSE Linux Enterprise Server version was released. Thus, the databases may not necessarily indicate the correct status, but only provide an approximation.

http://pages.cs.wisc.edu/~ghost/

The Ghostscript Web page.

/usr/share/doc/packages/ghostscript-library/catalog.devices

List of included drivers.

13.1. The Workflow of the Printing System

The user creates a print job. The print job consists of the data to print plus information for the spooler, such as the name of the printer or the name of the print queue, and optionally, information for the filter, such as printer-specific options.

At least one dedicated print queue exists for every printer. The spooler holds the print job in the queue until the desired printer is ready to receive data. When the printer is ready, the spooler sends the data through the filter and back-end to the printer.

The filter converts the data generated by the application that is printing (usually PostScript or PDF, but also ASCII, JPEG, etc.) into printer-specific data (PostScript, PCL, ESC/P, etc.). The features of the printer are described in the PPD files. A PPD file contains printer-specific options with the parameters needed to enable them on the printer. The filter system makes sure that options selected by the user are enabled.

If you use a PostScript printer, the filter system converts the data into printer-specific PostScript. This does not require a printer driver. If you use a non-PostScript printer, the filter system converts the data into printer-specific data. This requires a printer driver suitable for your printer. The back-end receives the printer-specific data from the filter then passes it to the printer.

13.2. Methods and Protocols for Connecting Printers

There are various possibilities for connecting a printer to the system. The configuration of the CUPS print system does not distinguish between a local printer and a printer connected to the system over the network.

►System z: Printers and similar devices provided by the z/VM that connect locally with the IBM System z mainframes are not supported by CUPS or LPRng. On these platforms, printing is only possible over the network. The cabling for network printers must be installed according to the instructions of the printer manufacturer.

[Warning]Changing Cable Connections in a Running System

When connecting the printer to the machine, do not forget that only USB devices can be plugged in or unplugged during operation. To avoid damaging your system or printer, shut down the system before changing any connections that are not USB.

13.3. Installing the Software

PPD (PostScript printer description) is the computer language that describes the properties, like resolution, and options, such as the availability of a duplex unit. These descriptions are required for using various printer options in CUPS. Without a PPD file, the print data would be forwarded to the printer in a raw state, which is usually not desired. During the installation of SUSE Linux Enterprise Server, many PPD files are pre-installed.

To configure a PostScript printer, the best approach is to get a suitable PPD file. Many PPD files are available in the package manufacturer-PPDs, which is automatically installed within the scope of the standard installation. See Section 13.6.2, “PPD Files in Various Packages” and Section 13.7.2, “No Suitable PPD File Available for a PostScript Printer”.

New PPD files can be stored in the directory /usr/share/cups/model/ or added to the print system with YaST as described in Section “Adding Drivers with YaST” (Chapter 8, Setting Up Hardware Components with YaST, ↑Deployment Guide). Subsequently, the PPD file can be selected during the printer setup.

Be careful if a printer manufacturer wants you to install entire software packages. First, this kind of installation may result in the loss of the support provided by SUSE Linux Enterprise Server and second, print commands may work differently and the system may no longer be able to address devices of other manufacturers. For this reason, the installation of manufacturer software is not recommended.

13.4. Network Printers

A network printer can support various protocols, some of them even concurrently. Although most of the supported protocols are standardized, some manufacturers modify the standard. Manufacturers then provide drivers for only a few operating systems. Unfortunately, Linux drivers are rarely provided. The current situation is such that you cannot act on the assumption that every protocol works smoothly in Linux. Therefore, you may have to experiment with various options to achieve a functional configuration.

CUPS supports the socket, LPD, IPP and smb protocols.

socket

Socket refers to a connection in which the plain print data is sent directly to a TCP socket. Some of the socket port numbers that are commonly used are 9100 or 35. The device URI (uniform resource identifier) syntax is: socket://IP.of.the.printer:port, for example: socket://192.168.2.202:9100/.

LPD (Line Printer Daemon)

The LPD protocol is described in RFC 1179. Under this protocol, some job-related data, such as the ID of the print queue, is sent before the actual print data is sent. Therefore, a print queue must be specified when configuring the LPD protocol. The implementations of diverse printer manufacturers are flexible enough to accept any name as the print queue. If necessary, the printer manual should indicate what name to use. LPT, LPT1, LP1 or similar names are often used. The port number for an LPD service is 515. An example device URI is lpd://192.168.2.202/LPT1.

IPP (Internet Printing Protocol)

IPP is a relatively new protocol (1999) based on the HTTP protocol. With IPP, more job-related data is transmitted than with the other protocols. CUPS uses IPP for internal data transmission. The name of the print queue is necessary to configure IPP correctly. The port number for IPP is 631. Example device URIs are ipp://192.168.2.202/ps and ipp://192.168.2.202/printers/ps.

SMB (Windows Share)

CUPS also supports printing on printers connected to Windows shares. The protocol used for this purpose is SMB. SMB uses the port numbers 137, 138 and 139. Example device URIs are smb://user:password@workgroup/smb.example.com/printer, smb://user:password@smb.example.com/printer, and smb://smb.example.com/printer.

The protocol supported by the printer must be determined before configuration. If the manufacturer does not provide the needed information, the command nmap (which comes with the nmap package) can be used to ascertain the protocol. nmap checks a host for open ports. For example:

nmap -p 35,137-139,515,631,9100-10000 printerIP

13.4.1. Configuring CUPS with Command Line Tools

CUPS can be configured with command line tools like lpinfo, lpadmin and lpoptions. You need a device URI consisting of a back-end, such as parallel, and parameters. To determine valid device URIs on your system use the command lpinfo -v | grep ":/":

# lpinfo -v | grep ":/"
direct usb://ACME/FunPrinter%20XL
direct parallel:/dev/lp0

With lpadmin the CUPS server administrator can add, remove or manage print queues. To add a print queue, use the following syntax:

lpadmin -p queue -v device-URI -P PPD-file -E

Then the device (-v) is available as queue (-p), using the specified PPD file (-P). This means that you must know the PPD file and the device URI to configure the printer manually.

Do not use -E as the first option. For all CUPS commands, -E as the first argument sets use of an encrypted connection. To enable the printer, -E must be used as shown in the following example:

lpadmin -p ps -v parallel:/dev/lp0 -P \
/usr/share/cups/model/Postscript.ppd.gz -E

The following example configures a network printer:

lpadmin -p ps -v socket://192.168.2.202:9100/ -P \
/usr/share/cups/model/Postscript-level1.ppd.gz -E

For more options of lpadmin, see the man page of lpadmin(8).

During printer setup, certain options are set as default. These options can be modified for every print job (depending on the print tool used). Changing these default options with YaST is also possible. Using command line tools, set default options as follows:

  1. First, list all options:

    lpoptions -p queue -l

    Example:

    Resolution/Output Resolution: 150dpi *300dpi 600dpi

    The activated default option is identified by a preceding asterisk (*).

  2. Change the option with lpadmin:

    lpadmin -p queue -o Resolution=600dpi
  3. Check the new setting:

    lpoptions -p queue -l
    
    Resolution/Output Resolution: 150dpi 300dpi *600dpi

When a normal user runs lpoptions, the settings are written to ~/.cups/lpoptions. However, root settings are written to /etc/cups/lpoptions.

13.5. Printing from the Command Line

To print from the command line, enter lp -d queuename filename, substituting the corresponding names for queuename and filename.

Some applications rely on the lp command for printing. In this case, enter the correct command in the application's print dialog, usually without specifying filename, for example, lp -d queuename.

13.6. Special Features in SUSE Linux Enterprise Server

A number of CUPS features have been adapted for SUSE Linux Enterprise Server. Some of the most important changes are covered here.

13.6.1. CUPS and Firewall

After having performed a default installation of SUSE Linux Enterprise Server, SuSEFirewall2 is active and the network interfaces are configured to be in the External Zone which blocks incoming traffic. More information about the SuSEFirewall2 configuration is available in Section “SuSEfirewall2” (Chapter 15, Masquerading and Firewalls, ↑Security Guide).

13.6.1.1. CUPS Client

Normally, a CUPS client runs on a regular workstation located in a trusted network environment behind a firewall. In this case it is recommended to configure the network interface to be in the Internal Zone, so the workstation is reachable from within the network.

13.6.1.2. CUPS Server

If the CUPS server is part of a trusted network environment protected by a firewall, the network interface should be configured to be in the Internal Zone of the firewall. It is not recommended to set up a CUPS server in an untrusted network environment unless you take care that it is protected by special firewall rules and secure settings in the CUPS configuration.

13.6.2. PPD Files in Various Packages

The YaST printer configuration sets up the queues for CUPS using the PPD files installed in /usr/share/cups/model. To find the suitable PPD files for the printer model, YaST compares the vendor and model determined during hardware detection with the vendors and models in all PPD files. For this purpose, the YaST printer configuration generates a database from the vendor and model information extracted from the PPD files.

The configuration using only PPD files and no other information sources has the advantage that the PPD files in /usr/share/cups/model can be modified freely. For example, if you only have PostScript printers, normally you do not need the Foomatic PPD files in the cups-drivers package or the Gutenprint PPD files in the gutenprint package. Instead, the PPD files for your PostScript printers can be copied directly to /usr/share/cups/model (if they do not already exist in the manufacturer-PPDs package) to achieve an optimum configuration for your printers.

13.6.2.1. CUPS PPD Files in the cups Package

The generic PPD files in the cups package have been complemented with adapted Foomatic PPD files for PostScript level 1 and level 2 printers:

  • /usr/share/cups/model/Postscript-level1.ppd.gz

  • /usr/share/cups/model/Postscript-level2.ppd.gz

13.6.2.2. PPD Files in the cups-drivers Package

Normally, the Foomatic printer filter foomatic-rip is used together with Ghostscript for non-PostScript printers. Suitable Foomatic PPD files have the entries *NickName: ... Foomatic/Ghostscript driver and *cupsFilter: ... foomatic-rip. These PPD files are located in the cups-drivers package.

YaST generally prefers a manufacturer-PPD file. However, when no suitable manufacturer-PPD file exists, a Foomatic PPD file with the entry *NickName: ... Foomatic ... (recommended) is selected.

13.6.2.3. Gutenprint PPD Files in the gutenprint Package

Instead of foomatic-rip, the CUPS filter rastertogutenprint from Gutenprint (formerly known as GIMP-Print) can be used for many non-PostScript printers. This filter and suitable Gutenprint PPD files are available in the gutenprint package. The Gutenprint PPD files are located in /usr/share/cups/model/gutenprint/ and have the entries *NickName: ... CUPS+Gutenprint and *cupsFilter: ... rastertogutenprint.

13.6.2.4. PPD Files from Printer Manufacturers in the manufacturer-PPDs Package

The manufacturer-PPDs package contains PPD files from printer manufacturers that are released under a sufficiently liberal license. PostScript printers should be configured with the suitable PPD file of the printer manufacturer, because this file enables the use of all functions of the PostScript printer. YaST prefers a PPD file from the manufacturer-PPDs. YaST cannot use a PPD file from the manufacturer-PPDs package if the model name does not match. This may happen if the manufacturer-PPDs package contains only one PPD file for similar models, like Funprinter 12xx series. In this case, select the respective PPD file manually in YaST.

13.7. Troubleshooting

The following sections cover some of the most frequently encountered printer hardware and software problems and ways to solve or circumvent these problems. Among the topics covered are GDI printers, PPD files and port configuration. Common network printer problems, defective printouts, and queue handling are also addressed.

13.7.1. Printers without Standard Printer Language Support

These printers do not support any common printer language and can only be addressed with special proprietary control sequences. Therefore they can only work with the operating system versions for which the manufacturer delivers a driver. GDI is a programming interface developed by Microsoft* for graphics devices. Usually the manufacturer delivers drivers only for Windows, and since the Windows driver uses the GDI interface these printers are also called GDI printers. The actual problem is not the programming interface, but the fact that these printers can only be addressed with the proprietary printer language of the respective printer model.

Some GDI printers can be switched to operate either in GDI mode or in one of the standard printer languages. See the manual of the printer whether this is possible. Some models require special Windows software to do the switch (note that the Windows printer driver may always switch the printer back into GDI mode when printing from Windows). For other GDI printers there are extension modules for a standard printer language available.

Some manufacturers provide proprietary drivers for their printers. The disadvantage of proprietary printer drivers is that there is no guarantee that these work with the installed print system or that they are suitable for the various hardware platforms. In contrast, printers that support a standard printer language do not depend on a special print system version or a special hardware platform.

Instead of spending time trying to make a proprietary Linux driver work, it may be more cost-effective to purchase a printer which supports a standard printer language (preferably PostScript). This would solve the driver problem once and for all, eliminating the need to install and configure special driver software and obtain driver updates that may be required due to new developments in the print system.

13.7.2. No Suitable PPD File Available for a PostScript Printer

If the manufacturer-PPDs package does not contain a suitable PPD file for a PostScript printer, it should be possible to use the PPD file from the driver CD of the printer manufacturer or download a suitable PPD file from the Web page of the printer manufacturer.

If the PPD file is provided as a zip archive (.zip) or a self-extracting zip archive (.exe), unpack it with unzip. First, review the license terms of the PPD file. Then use the cupstestppd utility to check if the PPD file complies with Adobe PostScript Printer Description File Format Specification, version 4.3. If the utility returns FAIL, the errors in the PPD files are serious and are likely to cause major problems. The problem spots reported by cupstestppd should be eliminated. If necessary, ask the printer manufacturer for a suitable PPD file.

13.7.3. Parallel Ports

The safest approach is to connect the printer directly to the first parallel port and to select the following parallel port settings in the BIOS:

  • I/O address: 378 (hexadecimal)

  • Interrupt: irrelevant

  • Mode: Normal, SPP, or Output Only

  • DMA: disabled

If the printer cannot be addressed on the parallel port despite these settings, enter the I/O address explicitly in accordance with the setting in the BIOS in the form 0x378 in /etc/modprobe.conf. If there are two parallel ports that are set to the I/O addresses 378 and 278 (hexadecimal), enter these in the form 0x378,0x278.

If interrupt 7 is free, it can be activated with the entry shown in Example 13.1, “/etc/modprobe.conf: Interrupt Mode for the First Parallel Port”. Before activating the interrupt mode, check the file /proc/interrupts to see which interrupts are already in use. Only the interrupts currently being used are displayed. This may change depending on which hardware components are active. The interrupt for the parallel port must not be used by any other device. If you are not sure, use the polling mode with irq=none.

Example 13.1. /etc/modprobe.conf: Interrupt Mode for the First Parallel Port

alias parport_lowlevel parport_pc
options parport_pc io=0x378 irq=7

13.7.4. Network Printer Connections

Identifying Network Problems

Connect the printer directly to the computer. For test purposes, configure the printer as a local printer. If this works, the problems are related to the network.

Checking the TCP/IP Network

The TCP/IP network and name resolution must be functional.

Checking a Remote lpd

Use the following command to test if a TCP connection can be established to lpd (port 515) on host:

netcat -z host 515 && echo ok || echo failed

If the connection to lpd cannot be established, lpd may not be active or there may be basic network problems.

As the user root, use the following command to query a (possibly very long) status report for queue on remote host, provided the respective lpd is active and the host accepts queries:

echo -e "\004queue" \
| netcat -w 2 -p 722 host 515

If lpd does not respond, it may not be active or there may be basic network problems. If lpd responds, the response should show why printing is not possible on the queue on host. If you receive a response like that shown in Example 13.2, “Error Message from lpd, the problem is caused by the remote lpd.

Example 13.2. Error Message from lpd

lpd: your host does not have line printer access
lpd: queue does not exist
printer: spooling disabled
printer: printing disabled

Checking a Remote cupsd

A CUPS network server can broadcast its queues by default every 30 seconds on UDP port 631. Accordingly, the following command can be used to test whether there is a broadcasting CUPS network server in the network. Make sure to stop your local CUPS daemon before executing the command.

netcat -u -l -p 631 & PID=$! ; sleep 40 ; kill $PID

If a broadcasting CUPS network server exists, the output appears as shown in Example 13.3, “Broadcast from the CUPS Network Server”.

Example 13.3. Broadcast from the CUPS Network Server

ipp://192.168.2.202:631/printers/queue

►System z: Take into account that IBM System z Ethernet devices do not receive broadcasts by default.

The following command can be used to test if a TCP connection can be established to cupsd (port 631) on host:

netcat -z host 631 && echo ok || echo failed

If the connection to cupsd cannot be established, cupsd may not be active or there may be basic network problems. lpstat -h host -l -t returns a (possibly very long) status report for all queues on host, provided the respective cupsd is active and the host accepts queries.

The next command can be used to test if the queue on host accepts a print job consisting of a single carriage-return character. Nothing should be printed. Possibly, a blank page may be ejected.

echo -en "\r" \
| lp -d queue -h host
Troubleshooting a Network Printer or Print Server Box

Spoolers running in a print server box sometimes cause problems when they have to deal with multiple print jobs. Since this is caused by the spooler in the print server box, there no way to resolve this issue. As a work-around, circumvent the spooler in the print server box by addressing the printer connected to the print server box directly with the TCP socket. See Section 13.4, “Network Printers”.

In this way, the print server box is reduced to a converter between the various forms of data transfer (TCP/IP network and local printer connection). To use this method, you need to know the TCP port on the print server box. If the printer is connected to the print server box and turned on, this TCP port can usually be determined with the nmap utility from the nmap package some time after the print server box is powered up. For example, nmap IP-address may deliver the following output for a print server box:

Port       State       Service
23/tcp     open        telnet
80/tcp     open        http
515/tcp    open        printer
631/tcp    open        cups
9100/tcp   open        jetdirect

This output indicates that the printer connected to the print server box can be addressed via TCP socket on port 9100. By default, nmap only checks a number of commonly known ports listed in /usr/share/nmap/nmap-services. To check all possible ports, use the command nmap -p from_port-to_port IP-address. This may take some time. For further information, refer to the man page of nmap.

Enter a command like

echo -en "\rHello\r\f" | netcat -w 1 IP-address port
cat file | netcat -w 1 IP-address port

to send character strings or files directly to the respective port to test if the printer can be addressed on this port.

13.7.5. Defective Printouts without Error Message

For the print system, the print job is completed when the CUPS back-end completes the data transfer to the recipient (printer). If further processing on the recipient fails (for example, if the printer is not able to print the printer-specific data) the print system does not notice this. If the printer is not able to print the printer-specific data, select a PPD file that is more suitable for the printer.

13.7.6. Disabled Queues

If the data transfer to the recipient fails entirely after several attempts, the CUPS back-end, such as USB or socket, reports an error to the print system (to cupsd). The back-end determines how many unsuccessful attempts are appropriate until the data transfer is reported as impossible. As further attempts would be in vain, cupsd disables printing for the respective queue. After eliminating the cause of the problem, the system administrator must re-enable printing with the command cupsenable.

13.7.7. CUPS Browsing: Deleting Print Jobs

If a CUPS network server broadcasts its queues to the client hosts via browsing and a suitable local cupsd is active on the client hosts, the client cupsd accepts print jobs from applications and forwards them to the cupsd on the server. When cupsd on the server accepts a print job, it is assigned a new job number. Therefore, the job number on the client host is different from the job number on the server. As a print job is usually forwarded immediately, it cannot be deleted with the job number on the client host This is because the client cupsd regards the print job as completed as soon as it has been forwarded to the server cupsd.

When it becomes desirable to delete the print job on the server, use a command such as lpstat -h cups.example.com -o to determine the job number on the server, provided the server has not already completed the print job (that is, sent it completely to the printer). Using this job number, the print job on the server can be deleted:

cancel -h cups.example.com queue-jobnumber

13.7.8. Defective Print Jobs and Data Transfer Errors

If you switch the printer off or shut down the computer during the printing process, print jobs remain in the queue. Printing resumes when the computer (or the printer) is switched back on. Defective print jobs must be removed from the queue with cancel.

If a print job is defective or an error occurs in the communication between the host and the printer, the printer prints numerous sheets of paper with unintelligible characters, because it is unable to process the data correctly. To rectify this situation, follow these steps:

  1. To stop printing, remove all paper from ink jet printers or open the paper trays of laser printers. High-quality printers have a button for canceling the current printout.

  2. The print job may still be in the queue, because jobs are only removed after they are sent completely to the printer. Use lpstat -o or lpstat -h cups.example.com -o to check which queue is currently printing. Delete the print job with cancel queue-jobnumber or cancel -h cups.example.com queue-jobnumber.

  3. Some data may still be transferred to the printer even though the print job has been deleted from the queue. Check if a CUPS back-end process is still running for the respective queue and terminate it. For example, for a printer connected to the parallel port, the command fuser -k /dev/lp0 can be used to terminate all processes that are still accessing the printer (more precisely: the parallel port).

  4. Reset the printer completely by switching it off for some time. Then insert the paper and turn on the printer.

13.7.9. Debugging the CUPS Print System

Use the following generic procedure to locate problems in the CUPS print system:

  1. Set LogLevel debug in /etc/cups/cupsd.conf.

  2. Stop cupsd.

  3. Remove /var/log/cups/error_log* to avoid having to search through very large log files.

  4. Start cupsd.

  5. Repeat the action that led to the problem.

  6. Check the messages in /var/log/cups/error_log* to identify the cause of the problem.

13.7.10. For More Information

Solutions to many specific problems are presented in the SUSE Knowledgebase (http://www.suse.com/support/). Locate the relevant articles with a text search for CUPS.

Chapter 14. Dynamic Kernel Device Management with udev

The kernel can add or remove almost any device in a running system. Changes in the device state (whether a device is plugged in or removed) need to be propagated to userspace. Devices need to be configured as soon as they are plugged in and recognized. Users of a certain device need to be informed about any changes in this device's recognized state. udev provides the needed infrastructure to dynamically maintain the device node files and symbolic links in the /dev directory. udev rules provide a way to plug external tools into the kernel device event processing. This enables you to customize udev device handling by, for example, adding certain scripts to execute as part of kernel device handling, or request and import additional data to evaluate during device handling.

14.1. The /dev Directory

The device nodes in the /dev directory provide access to the corresponding kernel devices. With udev, the /dev directory reflects the current state of the kernel. Every kernel device has one corresponding device file. If a device is disconnected from the system, the device node is removed.

The content of the /dev directory is kept on a temporary file system and all files are rendered at every system start-up. Manually created or modified files do not, by design, survive a reboot. Static files and directories that should always be present in the /dev directory regardless of the state of the corresponding kernel device can be placed in the /lib/udev/devices directory. At system start-up, the contents of that directory is copied to the /dev directory with the same ownership and permissions as the files in /lib/udev/devices.

14.2. Kernel uevents and udev

The required device information is exported by the sysfs file system. For every device the kernel has detected and initialized, a directory with the device name is created. It contains attribute files with device-specific properties.

Every time a device is added or removed, the kernel sends a uevent to notify udev of the change. The udev daemon reads and parses all provided rules from the /etc/udev/rules.d/*.rules files once at start-up and keeps them in memory. If rules files are changed, added or removed, the daemon can reload the in-memory representation of all rules with the command udevadm control reload_rules. This is also done when running /etc/init.d/boot.udev reload. For more details on udev rules and their syntax, refer to Section 14.6, “Influencing Kernel Device Event Handling with udev Rules”.

Every received event is matched against the set of provides rules. The rules can add or change event environment keys, request a specific name for the device node to create, add symlinks pointing to the node or add programs to run after the device node is created. The driver core uevents are received from a kernel netlink socket.

14.3. Drivers, Kernel Modules and Devices

The kernel bus drivers probe for devices. For every detected device, the kernel creates an internal device structure while the driver core sends a uevent to the udev daemon. Bus devices identify themselves by a specially-formatted ID, which tells what kind of device it is. Usually these IDs consist of vendor and product ID and other subsystem-specific values. Every bus has its own scheme for these IDs, called MODALIAS. The kernel takes the device information, composes a MODALIAS ID string from it and sends that string along with the event. For a USB mouse, it looks like this:

MODALIAS=usb:v046DpC03Ed2000dc00dsc00dp00ic03isc01ip02

Every device driver carries a list of known aliases for devices it can handle. The list is contained in the kernel module file itself. The program depmod reads the ID lists and creates the file modules.alias in the kernel's /lib/modules directory for all currently available modules. With this infrastructure, module loading is as easy as calling modprobe for every event that carries a MODALIAS key. If modprobe $MODALIAS is called, it matches the device alias composed for the device with the aliases provided by the modules. If a matching entry is found, that module is loaded. All this is automatically triggered by udev.

14.4. Booting and Initial Device Setup

All device events happening during the boot process before the udev daemon is running are lost, because the infrastructure to handle these events resides on the root file system and is not available at that time. To cover that loss, the kernel provides a uevent file located in the device directory of every device in the sysfs file system. By writing add to that file, the kernel resends the same event as the one lost during boot. A simple loop over all uevent files in /sys triggers all events again to create the device nodes and perform device setup.

As an example, a USB mouse present during boot may not be initialized by the early boot logic, because the driver is not available at that time. The event for the device discovery was lost and failed to find a kernel module for the device. Instead of manually searching for possibly connected devices, udev just requests all device events from the kernel after the root file system is available, so the event for the USB mouse device just runs again. Now it finds the kernel module on the mounted root file system and the USB mouse can be initialized.

From userspace, there is no visible difference between a device coldplug sequence and a device discovery during runtime. In both cases, the same rules are used to match and the same configured programs are run.

14.5. Monitoring the Running udev Daemon

The program udevadm monitor can be used to visualize the driver core events and the timing of the udev event processes.

UEVENT[1185238505.276660] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb)
UDEV  [1185238505.279198] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb)
UEVENT[1185238505.279527] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb)
UDEV  [1185238505.285573] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb)
UEVENT[1185238505.298878] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10 (input)
UDEV  [1185238505.305026] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10 (input)
UEVENT[1185238505.305442] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/mouse2 (input)
UEVENT[1185238505.306440] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/event4 (input)
UDEV  [1185238505.325384] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/event4 (input)
UDEV  [1185238505.342257] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/mouse2 (input)

The UEVENT lines show the events the kernel has sent over netlink. The UDEV lines show the finished udev event handlers. The timing is printed in microseconds. The time between UEVENT and UDEV is the time udev took to process this event or the udev daemon has delayed its execution to synchronize this event with related and already running events. For example, events for hard disk partitions always wait for the main disk device event to finish, because the partition events may rely on the data that the main disk event has queried from the hardware.

udevadm monitor --env shows the complete event environment:

ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10
SUBSYSTEM=input
SEQNUM=1181
NAME="Logitech USB-PS/2 Optical Mouse"
PHYS="usb-0000:00:1d.2-1/input0"
UNIQ=""
EV=7
KEY=70000 0 0 0 0
REL=103
MODALIAS=input:b0003v046DpC03Ee0110-e0,1,2,k110,111,112,r0,1,8,amlsfw

udev also sends messages to syslog. The default syslog priority that controls which messages are sent to syslog is specified in the udev configuration file /etc/udev/udev.conf. The log priority of the running daemon can be changed with udevadm control log_priority=level/number.

14.6. Influencing Kernel Device Event Handling with udev Rules

A udev rule can match any property the kernel adds to the event itself or any information that the kernel exports to sysfs. The rule can also request additional information from external programs. Every event is matched against all provided rules. All rules are located in the /etc/udev/rules.d directory.

Every line in the rules file contains at least one key value pair. There are two kinds of keys, match and assignment keys. If all match keys match their values, the rule is applied and the assignment keys are assigned the specified value. A matching rule may specify the name of the device node, add symlinks pointing to the node or run a specified program as part of the event handling. If no matching rule is found, the default device node name is used to create the device node. Detailed information about the rule syntax and the provided keys to match or import data are described in the udev man page. The following example rules provide a basic introduction to udev rule syntax. The example rules are all taken from the udev default rule set that is located under /etc/udev/rules.d/50-udev-default.rules.

Example 14.1. Example udev Rules

# console
KERNEL=="console", MODE="0600", OPTIONS="last_rule"

# serial devices
KERNEL=="ttyUSB*", ATTRS{product}=="[Pp]alm*Handheld*", SYMLINK+="pilot"

# printer
SUBSYSTEM=="usb", KERNEL=="lp*", NAME="usb/%k", SYMLINK+="usb%k", GROUP="lp"

# kernel firmware loader
SUBSYSTEM=="firmware", ACTION=="add", RUN+="firmware.sh"

The console rule consists of three keys: one match key (KERNEL) and two assign keys (MODE, OPTIONS). The KERNEL match rule searches the device list for any items of the type console. Only exact matches are valid and trigger this rule to be executed. The MODE key assigns special permissions to the device node, in this case, read and write permissions to the owner of this device only. The OPTIONS key makes this rule the last rule to be applied to any device of this type. Any later rule matching this particular device type does not have any effect.

The serial devices rule is not available in 50-udev-default.rules anymore, but it is still worth considering. It consists of two match keys (KERNEL and ATTRS) and one assign key (SYMLINK). The KERNEL key searches for all devices of the ttyUSB type. Using the * wild card, this key matches several of these devices. The second match key, ATTRS, checks whether the product attribute file in sysfs for any ttyUSB device contains a certain string. The assign key (SYMLINK) triggers the addition of a symbolic link to this device under /dev/pilot. The operator used in this key (+=) tells udev to additionally perform this action, even if previous or later rules add other symbolic links. As this rule contains two match keys, it is only applied if both conditions are met.

The printer rule deals with USB printers and contains two match keys which must both apply to get the entire rule applied (SUBSYSTEM and KERNEL). Three assign keys deal with the naming for this device type (NAME), the creation of symbolic device links (SYMLINK) and the group membership for this device type (GROUP). Using the * wild card in the KERNEL key makes it match several lp printer devices. Substitutions are used in both, the NAME and the SYMLINK keys to extend these strings by the internal device name. For example, the symlink to the first lp USB printer would read /dev/usblp0.

The kernel firmware loader rule makes udev load additional firmware by an external helper script during runtime. The SUBSYSTEM match key searches for the firmware subsystem. The ACTION key checks whether any device belonging to the firmware subsystem has been added. The RUN+= key triggers the execution of the firmware.sh script to locate the firmware that is to be loaded.

Some general characteristics are common to all rules:

  • Each rule consists of one or more key value pairs separated by a comma.

  • A key's operation is determined by the operator. udev rules support several different operators.

  • Each given value must be enclosed by quotation marks.

  • Each line of the rules file represents one rule. If a rule is longer than just one line, use \ to join the different lines just as you would do in shell syntax.

  • udev rules support a shell-style pattern that matches the *, ?, and [] patterns.

  • udev rules support substitutions.

14.6.1. Using Operators in udev Rules

Creating keys you can choose from several different operators, depending on the type of key you want to create. Match keys will normally just be used to find a value that either matches or explicitly mismatches the search value. Match keys contain either of the following operators:

==

Compare for equality. If the key contains a search pattern, all results matching this pattern are valid.

!=

Compare for non-equality. If the key contains a search pattern, all results matching this pattern are valid.

Any of the following operators can be used with assign keys:

=

Assign a value to a key. If the key previously consisted of a list of values, the key resets and only the single value is assigned.

+=

Add a value to a key that contains a list of entries.

:=

Assign a final value. Disallow any later change by later rules.

14.6.2. Using Substitutions in udev Rules

udev rules support the use of placeholders and substitutions. Use them in a similar fashion as you would do in any other scripts. The following substitutions can be used with udev rules:

%r, $root

The device directory, /dev by default.

%p, $devpath

The value of DEVPATH.

%k, $kernel

The value of KERNEL or the internal device name.

%n, $number

The device number.

%N, $tempnode

The temporary name of the device file.

%M, $major

The major number of the device.

%m, $minor

The minor number of the device.

%s{attribute}, $attr{attribute}

The value of a sysfs attribute (specified by attribute).

%E{variable}, $attr{variable}

The value of an environment variable (specified by variable).

%c, $result

The output of PROGRAM.

%%

The % character.

$$

The $ character.

14.6.3. Using udev Match Keys

Match keys describe conditions that must be met before a udev rule can be applied. The following match keys are available:

ACTION

The name of the event action, for example, add or remove when adding or removing a device.

DEVPATH

The device path of the event device, for example, DEVPATH=/bus/pci/drivers/ipw3945 to search for all events related to the ipw3945 driver.

KERNEL

The internal (kernel) name of the event device.

SUBSYSTEM

The subsystem of the event device, for example, SUBSYSTEM=usb for all events related to USB devices.

ATTR{filename}

sysfs attributes of the event device. To match a string contained in the vendor attribute file name, you could use ATTR{vendor}=="On[sS]tream", for example.

KERNELS

Let udev search the device path upwards for a matching device name.

SUBSYSTEMS

Let udev search the device path upwards for a matching device subsystem name.

DRIVERS

Let udev search the device path upwards for a matching device driver name.

ATTRS{filename}

Let udev search the device path upwards for a device with matching sysfs attribute values.

ENV{key}

The value of an environment variable, for example, ENV{ID_BUS}="ieee1394 to search for all events related to the FireWire bus ID.

PROGRAM

Let udev execute an external program. To be successful, the program must return with exit code zero. The program's output, printed to stdout, is available to the RESULT key.

RESULT

Match the output string of the last PROGRAM call. Either include this key in the same rule as the PROGRAM key or in a later one.

14.6.4. Using udev Assign Keys

In contrast to the match keys described above, assign keys do not describe conditions that must be met. They assign values, names and actions to the device nodes maintained by udev.

NAME

The name of the device node to be created. Once a rule has set a node name, all other rules with a NAME key for this node are ignored.

SYMLINK

The name of a symlink related to the node to be created. Multiple matching rules can add symlinks to be created with the device node. You can also specify multiple symlinks for one node in one rule using the space character to separate the symlink names.

OWNER, GROUP, MODE

The permissions for the new device node. Values specified here overwrite anything that has been compiled in.

ATTR{key}

Specify a value to be written to a sysfs attribute of the event device. If the == operator is used, this key is also used to match against the value of a sysfs attribute.

ENV{key}

Tell udev to export a variable to the environment. If the == operator is used, this key is also used to match against an environment variable.

RUN

Tell udev to add a program to the list of programs to be executed for this device. Keep in mind to restrict this to very short tasks to avoid blocking further events for this device.

LABEL

Add a label where a GOTO can jump to.

GOTO

Tell udev to skip a number of rules and continue with the one that carries the label referenced by the GOTO key.

IMPORT{type}

Load variables into the event environment such as the output of an external program. udev imports variables of several different types. If no type is specified, udev tries to determine the type itself based on the executable bit of the file permissions.

  • program tells udev to execute an external program and import its output.

  • file tells udev to import a text file.

  • parent tells udev to import the stored keys from the parent device.

WAIT_FOR_SYSFS

Tells udev to wait for the specified sysfs file to be created for a certain device. For example, WAIT_FOR_SYSFS="ioerr_cnt" informs udev to wait until the ioerr_cnt file has been created.

OPTIONS

The OPTION key may have several possible values:

  • last_rule tells udev to ignore all later rules.

  • ignore_device tells udev to ignore this event completely.

  • ignore_remove tells udev to ignore all later remove events for the device.

  • all_partitions tells udev to create device nodes for all available partitions on a block device.

14.7. Persistent Device Naming

The dynamic device directory and the udev rules infrastructure make it possible to provide stable names for all disk devices—regardless of their order of recognition or the connection used for the device. Every appropriate block device the kernel creates is examined by tools with special knowledge about certain buses, drive types or file systems. Along with the dynamic kernel-provided device node name, udev maintains classes of persistent symbolic links pointing to the device:

/dev/disk
|-- by-id
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B -> ../../sda
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part1 -> ../../sda1
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part6 -> ../../sda6
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part7 -> ../../sda7
|   |-- usb-Generic_STORAGE_DEVICE_02773 -> ../../sdd
|   `-- usb-Generic_STORAGE_DEVICE_02773-part1 -> ../../sdd1
|-- by-label
|   |-- Photos -> ../../sdd1
|   |-- SUSE10 -> ../../sda7
|   `-- devel -> ../../sda6
|-- by-path
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0 -> ../../sda
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0-part1 -> ../../sda1
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0-part6 -> ../../sda6
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0-part7 -> ../../sda7
|   |-- pci-0000:00:1f.2-scsi-1:0:0:0 -> ../../sr0
|   |-- usb-02773:0:0:2 -> ../../sdd
|   |-- usb-02773:0:0:2-part1 -> ../../sdd1
`-- by-uuid
    |-- 159a47a4-e6e6-40be-a757-a629991479ae -> ../../sda7
    |-- 3e999973-00c9-4917-9442-b7633bd95b9e -> ../../sda6
    `-- 4210-8F8C -> ../../sdd1

14.8. Files used by udev

/sys/*

Virtual file system provided by the Linux kernel, exporting all currently known devices. This information is used by udev to create device nodes in /dev

/dev/*

Dynamically created device nodes and static content copied at boot time from /lib/udev/devices/*

The following files and directories contain the crucial elements of the udev infrastructure:

/etc/udev/udev.conf

Main udev configuration file.

/etc/udev/rules.d/*

udev event matching rules.

/lib/udev/devices/*

Static /dev content.

/lib/udev/*

Helper programs called from udev rules.

14.9. For More Information

For more information about the udev infrastructure, refer to the following man pages:

udev

General information about udev, keys, rules and other important configuration issues.

udevadm

udevadm can be used to control the runtime behavior of udev, request kernel events, manage the event queue and provide simple debugging mechanisms.

udevd

Information about the udev event managing daemon.

Chapter 15. The X Window System

The X Window System (X11) is the de facto standard for graphical user interfaces in UNIX. X is network-based, enabling applications started on one host to be displayed on another host connected over any kind of network (LAN or Internet). This chapter describes the setup and optimization of the X Window System environment, and provides background information about the use of fonts in SUSE® Linux Enterprise Server.

[Tip]IBM System z: Configuring the Graphical User Interface

IBM System z does not have any input or output devices supported by X.Org. Therefore, none of the configuration procedures described in this section apply. More relevant information for IBM System z can be found in Chapter 4, Installation on IBM System z (↑Deployment Guide).

15.1. Manually Configuring the X Window System

By default, the X Window System is configured with the SaX2 interface, described in Section “Setting Up Graphics Card and Monitor” (Chapter 8, Setting Up Hardware Components with YaST, ↑Deployment Guide). Alternatively it can be configured manually by editing its configuration files.

[Warning]Faulty X Configurations can Damage Your Hardware

Be very careful when configuring your X Window System. Never start the X Window System until the configuration is finished. A misconfigured system can cause irreparable damage to your hardware (this applies especially to fixed-frequency monitors). The creators of this book and SUSE Linux Enterprise Server cannot be held responsible for any resulting damage. This information has been carefully researched, but this does not guarantee that all methods presented here are correct and cannot damage your hardware.

The command sax2 creates the /etc/X11/xorg.conf file. This is the primary configuration file of the X Window System. Find all the settings here concerning your graphics card, mouse and monitor.

[Important]Using X -configure

Use X -configure to configure your X setup if previous tries with SUSE Linux Enterprise Server's SaX2 have failed. If your setup involves proprietary binary-only drivers, X -configure does not work.

The following sections describe the structure of the configuration file /etc/X11/xorg.conf. It consists of several sections, each one dealing with a certain aspect of the configuration. Each section starts with the keyword Section <designation> and ends with EndSection. The following convention applies to all sections:

Section "designation"
  entry 1
  entry 2
  entry n
EndSection 

The section types available are listed in Table 15.1, “Sections in /etc/X11/xorg.conf”.

Table 15.1. Sections in /etc/X11/xorg.conf

Type

Meaning

Files

The paths used for fonts and the RGB color table.

ServerFlags

General switches for the server behavior.

Module

A list of modules the server should load

InputDevice

Input devices like keyboards and special input devices (touchpads, joysticks, etc.) are configured in this section. Important parameters in this section are Driver and the options defining the Protocol and Device. You normally have one InputDevice section per device attached to the computer.

Monitor

The monitor used. Important elements of this section are the Identifier, which is referred to later in the Screen definition, the refresh rate VertRefresh and the synchronization frequency limits (HorizSync and VertRefresh). Settings are given in MHz, kHz and Hz. Normally, the server refuses any modeline that does not correspond with the specification of the monitor. This prevents too high frequencies from being sent to the monitor by accident.

Modes

The modeline parameters for the specific screen resolutions. These parameters can be calculated by SaX2 on the basis of the values given by the user and normally do not need to be changed. Intervene manually at this point if, for example, you want to connect a fixed frequency monitor. Find details of the meaning of individual number values in the HOWTO files in /usr/share/doc/howto/en/html/XFree86-Video-Timings-HOWTO (available in the howtoenh package). To calculate VESA modes manually, you can use the tool cvt. For example, to calculate a modeline for a 1680x1050@60Hz monitor, use the command cvt 1680 1050 60.

Device

A specific graphics card. It is referenced by its descriptive name. The options available in this section strongly depend on the driver used. For example, if you use the i810 driver, find more information about the available options in the manual page man 4 i810.

Screen

Combines a Monitor and a Device to form all the necessary settings for X.Org. In the Display subsection, specify the size of the virtual screen (Virtual), the ViewPort and the Modes used with this screen.

Note that some drivers demand that all of the used configurations must be present in the Display section at some place. For example, if you use a laptop and want to use an external monitor that is bigger than the internal LCD, it might be necessary to add a bigger resolution than supported by the internal LCD at the end of the Modes line.

ServerLayout

The layout of a single or multihead configuration. This section binds the input devices InputDevice and the display devices Screen.

DRI

Provides information for the Direct Rendering Infrastructure (DRI).


Monitor, Device and Screen are explained in more detail. Further information about the other sections can be found in the manual pages of X.Org and xorg.conf.

There can be several different Monitor and Device sections in xorg.conf. Even multiple Screen sections are possible. The ServerLayout section determines which of these sections is used.

15.1.1. Screen Section

The screen section combines a monitor with a device section and determines the resolution and color depth to use. A screen section might resemble Example 15.1, “Screen Section of the File /etc/X11/xorg.conf”.

Example 15.1. Screen Section of the File /etc/X11/xorg.conf

Section "Screen"1
  DefaultDepth  162
  SubSection "Display"3
    Depth       164
    Modes       "1152x864" "1024x768" "800x600"5
    Virtual     1152x8646
  EndSubSection
  SubSection "Display"
    Depth       24
    Modes       "1280x1024"
  EndSubSection
  SubSection "Display"
    Depth       32
    Modes "640x480"
  EndSubSection
  SubSection "Display"
    Depth        8
    Modes       "1280x1024"
  EndSubSection
  Device        "Device[0]"
  Identifier    "Screen[0]"7
  Monitor       "Monitor[0]"
EndSection

1

Section determines the section type, in this case Screen.

2

DefaultDepth determines the color depth to use by default unless another color depth is explicitly specified.

3

For each color depth, different Display subsections are specified.

4

Depth determines the color depth to be used with this set of Display settings. Possible values are 8, 15, 16, 24 and 32, though not all of these might be supported by all X server modules or resolutions.

5

The Modes section comprises a list of possible screen resolutions. The list is checked by the X server from left to right. For each resolution, the X server searches for a suitable Modeline in the Modes section. The Modeline depends on the capability of both the monitor and the graphics card. The Monitor settings determine the resulting Modeline.

The first resolution found is the Default mode. With Ctrl+Alt++ (on the number pad) switch to the next resolution in the list to the right. With Ctrl+Alt+ (on the number pad) switch to the previous. This enables you to vary the resolution while X is running.

6

The last line of the Display subsection with Depth 16 refers to the size of the virtual screen. The maximum possible size of a virtual screen depends on the amount of memory installed on the graphics card and the desired color depth, not on the maximum resolution of the monitor. If you omit this line, the virtual resolution is just the physical resolution. Because modern graphics cards have a large amount of video memory, you can create very large virtual desktops. However, you may no longer be able to use 3D functionality if you fill most of the video memory with a virtual desktop. If, for example, the card has 16 MB of video RAM, the virtual screen can take up to 4096x4096 pixels in size at 8-bit color depth. Especially for accelerated cards, however, it is not recommended to use all your memory for the virtual screen, because the card's memory is also used for several font and graphics caches.

7

The Identifier line (here Screen[0]) gives this section a defined name with which it can be uniquely referenced in the following ServerLayout section. The lines Device and Monitor specify the graphics card and the monitor that belong to this definition. These are just links to the Device and Monitor sections with their corresponding names or identifiers. These sections are discussed in detail below.

15.1.2. Device Section

A device section describes a specific graphics card. You can have as many device entries in xorg.conf as you like, provided their names are differentiated using the keyword Identifier. If you have more than one graphics card installed, the sections are simply numbered in order. The first one is called Device[0], the second one Device[1], and so on. The following file shows an excerpt from the Device section of a computer with a Matrox Millennium PCI graphics card (as configured by SaX2):

Section "Device"
  BoardName     "MGA2064W"
  BusID         "0:19:0"1
  Driver        "mga"2
  Identifier    "Device[0]"
  VendorName    "Matrox"
  Option        "sw_cursor"
EndSection

1

The BusID refers to the PCI or AGP slot in which the graphics card is installed. This matches the ID displayed by the command lspci. The X server needs details in decimal form, but lspci displays these in hexadecimal form. The value of BusID is automatically detected by SaX2.

2

The value of Driver is automatically set by SaX2 and specifies which driver to use for your graphics card. If the card is a Matrox Millennium, the driver module is called mga. The X server then searches through the ModulePath defined in the Files section in the drivers subdirectory. In a standard installation, this is the /usr/lib/xorg/modules/drivers directory or the /usr/lib64/xorg/modules/drivers directory for 64-Bit operating systems directory. _drv.o is added to the name, so, in the case of the mga driver, the driver file mga_drv.o is loaded.

The behavior of the X server or of the driver can also be influenced through additional options. An example of this is the option sw_cursor, which is set in the device section. This deactivates the hardware mouse cursor and depicts the mouse cursor using software. Depending on the driver module, there are various options available (which can be found in the description files of the driver modules in the directory /usr/share/doc/packages/package_name ). Generally valid options can also be found in the manual pages (man xorg.conf, man 4 <driver module>, and man 4 chips).

If the graphics card has multiple video connectors, it is possible to configure the different devices of this single card as one single view. Use SaX2 to set up your graphics interface this way.

15.1.3. Monitor and Modes Section

Like the Device sections, the Monitor and Modes sections describe one monitor each. The configuration file /etc/X11/xorg.conf can contain as many Monitor sections as desired. Each Monitor section references a Modes section with the line UseModes if available. If no Modes section is available for the Monitor section, the X server calculates appropriate values from the general synchronization values. The server layout section specifies which Monitor section is relevant.

Monitor definitions should only be set by experienced users. The modelines are an important part of the Monitor sections. Modelines set horizontal and vertical timings for the respective resolution. The monitor properties, especially the allowed frequencies, are stored in the Monitor section. Standard VESA modes can be generated with the utility cvt. For more information read the manual page of cvt man cvt.

[Warning]

Unless you have in-depth knowledge of monitor and graphics card functions, do not change the modelines, because this could severely damage your monitor.

Those who try to develop their own monitor descriptions should be very familiar with the documentation in /usr/share/X11/doc. Install the package xorg-x11-doc to find PDFs and HTML pages.

Manual specification of modelines is rarely required today. If you are using a modern multisync monitor, the allowed frequencies and optimal resolutions can, as a rule, be read directly from the monitor by the X server via DDC, as described in the SaX2 configuration section. If this is not possible for some reason, use one of the VESA modes included in the X server. This will work with most graphics card and monitor combinations.

15.2. Installing and Configuring Fonts

The installation of additional fonts in SUSE Linux Enterprise Server is very easy. Simply copy the fonts to any directory located in the X11 font path (see Section 15.2.1, “X11 Core Fonts”). To the enable use of the fonts, the installation directory should be a subdirectory of the directories configured in /etc/fonts/fonts.conf (see Section 15.2.2, “Xft”) or included into this file with /etc/fonts/suse-font-dirs.conf.

The following is an excerpt from /etc/fonts/fonts.conf. This file is the standard configuration file that should be appropriate for most configurations. It also defines the included directory /etc/fonts/conf.d. In this directory, all files or symbolic links starting with a two digit number are loaded by fontconfig. For a more detailed explanation of this functionality, have a look at /etc/fonts/conf.d/README.

<!-- Font directory list -->
<dir>/usr/share/fonts</dir>
<dir>/usr/X11R6/lib/X11/fonts</dir> 
<dir>/opt/kde3/share/fonts</dir>
<dir>/usr/local/share/fonts</dir>
<dir>~/.fonts</dir>

/etc/fonts/suse-font-dirs.conf is automatically generated to pull in fonts that ship with (mostly third party) applications like LibreOffice, Java or Adobe Reader. A typical entry would look like the following:

<dir>/usr/lib/Adobe/Reader9/Resource/Font</dir>
<dir>/usr/lib/Adobe/Reader9/Resource/Font/PFM</dir>
 

To install additional fonts system-wide, manually copy the font files to a suitable directory (as root), such as /usr/share/fonts/truetype. Alternatively, the task can be performed with the KDE font installer in the KDE Control Center. The result is the same.

Instead of copying the actual fonts, you can also create symbolic links. For example, you may want to do this if you have licensed fonts on a mounted Windows partition and want to use them. Subsequently, run SuSEconfig --module fonts .

SuSEconfig --module fonts executes the script /usr/sbin/fonts-config, which handles the font configuration. For more information on this script, refer to its manual page (man fonts-config ).

The procedure is the same for bitmap fonts, TrueType and OpenType fonts, and Type1 (PostScript) fonts. All these font types can be installed into any directory.

X.Org contains two completely different font systems: the old X11 core font system and the newly designed Xft and fontconfig system. The following sections briefly describe these two systems.

15.2.1. X11 Core Fonts

Today, the X11 core font system supports not only bitmap fonts but also scalable fonts, like Type1 fonts, TrueType, and OpenType fonts. Scalable fonts are only supported without anti-aliasing and subpixel rendering and the loading of large scalable fonts with glyphs for many languages may take a long time. Unicode fonts are also supported, but their use may be slow and require more memory.

The X11 core font system has a few inherent weaknesses. It is outdated and can no longer be extended in any meaningful way. Although it must be retained for reasons of backward compatibility, the more modern Xft and fontconfig system should be used if at all possible.

For its operation, the X server needs to know which fonts are available and where in the system it can find them. This is handled by a FontPath variable, which contains the path to all valid system font directories. In each of these directories, a file named fonts.dir lists the available fonts in this directory. The FontPath is generated by the X server at start-up. It searches for a valid fonts.dir file in each of the FontPath entries in the configuration file /etc/X11/xorg.conf. These entries are found in the Files section. Display the actual FontPath with xset q. This path may also be changed at runtime with xset. To add an additional path, use xset +fp <path>. To remove an unwanted path, use xset -fp <path>.

If the X server is already active, newly installed fonts in mounted directories can be made available with the command xset fp rehash. This command is executed by SuSEconfig --module fonts. Because the command xset needs access to the running X server, this only works if SuSEconfig --module fonts is started from a shell that has access to the running X server. The easiest way to achieve this is to acquire root permissions by entering su and the root password. su transfers the access permissions of the user who started the X server to the root shell. To check if the fonts were installed correctly and are available by way of the X11 core font system, use the command xlsfonts to list all available fonts.

By default, SUSE Linux Enterprise Server uses UTF-8 locales. Therefore, Unicode fonts should be preferred (font names ending with iso10646-1 in xlsfonts output). All available Unicode fonts can be listed with xlsfonts | grep iso10646-1. Nearly all Unicode fonts available in SUSE Linux Enterprise Server contain at least the glyphs needed for European languages (formerly encoded as iso-8859-*).

15.2.2. Xft

From the outset, the programmers of Xft made sure that scalable fonts including anti-aliasing are well supported. If Xft is used, the fonts are rendered by the application using the fonts, not by the X server as in the X11 core font system. In this way, the respective application has access to the actual font files and full control of how the glyphs are rendered. This constitutes the basis for the correct display of text in a number of languages. Direct access to the font files is very useful for embedding fonts for printing to make sure that the printout looks the same as the screen output.

In SUSE Linux Enterprise Server, the two desktop environments (KDE and GNOME), Mozilla and many other applications already use Xft by default. Xft is already used by more applications than the old X11 core font system.

Xft uses the fontconfig library for finding fonts and influencing how they are rendered. The properties of fontconfig are controlled by the global configuration file /etc/fonts/fonts.conf. Special configurations should be added to /etc/fonts/local.conf and the user-specific configuration file ~/.fonts.conf. Each of these fontconfig configuration files must begin with

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>

and end with

</fontconfig>

To add directories to search for fonts, append lines such as the following:

<dir>/usr/local/share/fonts/</dir>

However, this is usually not necessary. By default, the user-specific directory ~/.fonts is already entered in /etc/fonts/fonts.conf. Accordingly, all you need to do to install additional fonts is to copy them to ~/.fonts.

You can also insert rules that influence the appearance of the fonts. For example, enter

<match target="font">
 <edit name="antialias" mode="assign">
  <bool>false</bool>
 </edit>
</match>

to disable anti-aliasing for all fonts or

<match target="font">
 <test name="family">
  <string>Luxi Mono</string>
  <string>Luxi Sans</string>
 </test>
 <edit name="antialias" mode="assign">
 <bool>false</bool>
 </edit>
</match>

to disable anti-aliasing for specific fonts.

By default, most applications use the font names sans-serif (or the equivalent sans), serif, or monospace. These are not real fonts but only aliases that are resolved to a suitable font, depending on the language setting.

Users can easily add rules to ~/.fonts.conf to resolve these aliases to their favorite fonts:

<alias>
 <family>sans-serif</family>
 <prefer>
  <family>FreeSans</family>
 </prefer>
</alias>
<alias>
 <family>serif</family>
 <prefer>
  <family>FreeSerif</family>
 </prefer>
</alias>
<alias>
 <family>monospace</family>
 <prefer>
  <family>FreeMono</family>
 </prefer>
</alias>

Because nearly all applications use these aliases by default, this affects almost the entire system. Thus, you can easily use your favorite fonts almost everywhere without having to modify the font settings in the individual applications.

Use the command fc-list to find out which fonts are installed and available for use. For instance, the command fc-list returns a list of all fonts. To find out which of the available scalable fonts (:scalable=true) contain all glyphs required for Hebrew (:lang=he), their font names (family), their style (style), their weight (weight) and the name of the files containing the fonts, enter the following command:

fc-list ":lang=he:scalable=true" family style weight

The output of this command could look like the following:

Lucida Sans:style=Demibold:weight=200
DejaVu Sans:style=Bold Oblique:weight=200
Lucida Sans Typewriter:style=Bold:weight=200
DejaVu Sans:style=Oblique:weight=80
Lucida Sans Typewriter:style=Regular:weight=80
DejaVu Sans:style=Book:weight=80
DejaVu Sans:style=Bold:weight=200
Lucida Sans:style=Regular:weight=80

Important parameters that can be queried with fc-list:

Table 15.2. Parameters of fc-list

Parameter

Meaning and Possible Values

family

Name of the font family, for example, FreeSans.

foundry

The manufacturer of the font, for example, urw.

style

The font style, such as Medium, Regular, Bold, Italic or Heavy.

lang

The language that the font supports, for example, de for German, ja for Japanese, zh-TW for traditional Chinese or zh-CN for simplified Chinese.

weight

The font weight, such as 80 for regular or 200 for bold.

slant

The slant, usually 0 for none and 100 for italic.

file

The name of the file containing the font.

outline

true for outline fonts or false for other fonts.

scalable

true for scalable fonts or false for other fonts.

bitmap

true for bitmap fonts or false for other fonts.

pixelsize

Font size in pixels. In connection with fc-list, this option only makes sense for bitmap fonts.


15.3. For More Information

Install the packages xorg-x11-doc and howtoenh to get more in-depth information about X11. More information on the X11 development can be found on the project's home page at http://www.x.org.

Many of the drivers delivered with the package xorg-x11-driver-video are described in detail in a manual page. For example, if you use the nv driver, find more information about this driver in man 4 nv.

Information about third-party drivers should be available in /usr/share/doc/packages/<package_name>. For example, the documentation of x11-video-nvidiaG01 is available in /usr/share/doc/packages/x11-video-nvidiaG01 after the package was installed.

Chapter 16. Accessing File Systems with FUSE

Abstract

FUSE is the acronym for file system in userspace. This means you can configure and mount a file system as an unprivileged user. Normally, you have to be root for this task. FUSE alone is a kernel module. Combined with plug-ins, it allows you to extend FUSE to access almost all file systems like remote SSH connections, ISO images, and more.

16.1. Configuring FUSE

Before you can use FUSE, you have to install the package fuse. Depending which file system you want to use, you need additional plug-ins available as separate packages. FUSE plug-ins are not shipped with SUSE Linux Enterprise.

Generally you do not have to configure FUSE, you just use it. However, it is a good idea to create a directory where all your mount points are combined. For example, you can create a directory ~/mounts and insert your subdirectories for your different file systems there.

16.2. Available FUSE Plug-ins

FUSE is dependent on plug-ins. The following table lists common plug-ins. FUSE plug-ins are not shipped with SUSE Linux Enterprise.

Table 16.1. Available FUSE Plug-ins

fuseiso

mounts CD-ROM images with ISO9660 file systems in them

ntfs-3g

mount NTFS volumes (with read and write support)

sshfs

file system client based on SSH file transfer protocol

wdfs

mount WebDAV file systems


16.3. For More Information

See the home page http://fuse.sourceforge.net of FUSE for more information.

Part III. Mobile Computers

Chapter 17. Mobile Computing with Linux

Abstract

Mobile computing is mostly associated with laptops, PDAs and cellular phones (and the data exchange between them). Mobile hardware components, such as external hard disks, flash drives, or digital cameras, can be connected to laptops or desktop systems. A number of software components are involved in mobile computing scenarios and some applications are tailor-made for mobile use.

17.1. Laptops

The hardware of laptops differs from that of a normal desktop system. This is because criteria like exchangeability, space requirements and power consumption must be taken into account. The manufacturers of mobile hardware have developed standard interfaces like PCMCIA (Personal Computer Memory Card International Association), Mini PCI and Mini PCIe that can be used to extend the hardware of laptops. The standards cover memory cards, network interface cards, ISDN (and modem cards) and external hard disks.

[Tip]SUSE Linux Enterprise Server and Tablet PCs

SUSE Linux Enterprise Server also supports Tablet PCs. Tablet PCs come with a touchpad/digitizer that allows you to use a digital pen or even fingertips to edit data right on the screen instead of using mouse and keyboard. They are installed and configured much like any other system. For a detailed introduction to the installation and configuration of Tablet PCs, refer to Chapter 20, Using Tablet PCs.

17.1.1. Power Conservation

The inclusion of energy-optimized system components during laptop manufacturing contributes to their suitability for use without access to the electrical power grid. Their contribution towards conservation of power is at least as important as that of the operating system. SUSE® Linux Enterprise Server supports various methods that influence the power consumption of a laptop and have varying effects on the operating time under battery power. The following list is in descending order of contribution towards power conservation:

  • Throttling the CPU speed.

  • Switching off the display illumination during pauses.

  • Manually adjusting the display illumination.

  • Disconnecting unused, hotplug-enabled accessories (USB CD-ROM, external mouse, unused PCMCIA cards, WLAN, etc.).

  • Spinning down the hard disk when idling.

Detailed background information about power management in SUSE Linux Enterprise Server is provided in Chapter 19, Power Management.

17.1.2. Integration in Changing Operating Environments

Your system needs to adapt to changing operating environments when used for mobile computing. Many services depend on the environment and the underlying clients must be reconfigured. SUSE Linux Enterprise Server handles this task for you.

Figure 17.1. Integrating a Mobile Computer in an Existing Environment

Integrating a Mobile Computer in an Existing Environment

The services affected in the case of a laptop commuting back and forth between a small home network and an office network are:

Network

This includes IP address assignment, name resolution, Internet connectivity and connectivity to other networks.

Printing

A current database of available printers and an available print server must be present, depending on the network.

E-Mail and Proxies

As with printing, the list of the corresponding servers must be current.

X (Graphical Environment)

If your laptop is temporarily connected to a projector or an external monitor, different display configurations must be available.

SUSE Linux Enterprise Server offers several ways of integrating laptops into existing operating environments:

NetworkManager

NetworkManager is especially tailored for mobile networking on laptops. It provides a means to easily and automatically switch between network environments or different types of networks such as mobile broadband (such as GPRS, EDGE, or 3G), wireless LAN, and Ethernet. NetworkManager supports WEP and WPA-PSK encryption in wireless LANs. It also supports dial-up connections (with smpppd). Both desktop environments (GNOME and KDE) include a front-end for NetworkManager. For more information about the desktop applets, see Section 26.4, “Using KNetworkManager” and Section 26.5, “Using GNOME NetworkManager Applet”.

Table 17.1. Use Cases for NetworkManager

My computer…

Use NetworkManager

is a laptop

Yes

is sometimes attached to different networks

Yes

provides network services (such as DNS or DHCP)

No

only uses a static IP address

No


Use the YaST tools to configure networking whenever NetworkManager should not handle network configuration.

[Tip]DNS configuration and various types of network connections

If you travel frequently with your laptop and change different types of network connections, NetworkManager works fine when all DNS addresses are assigned correctly assigned with DHCP. If some of your connections use static DNS address(es), add it to the NETCONFIG_DNS_STATIC_SERVERS option in /etc/sysconfig/network/config.

SLP

The service location protocol (SLP) simplifies the connection of a laptop to an existing network. Without SLP, the administrator of a laptop usually requires detailed knowledge of the services available in a network. SLP broadcasts the availability of a certain type of service to all clients in a local network. Applications that support SLP can process the information dispatched by SLP and be configured automatically. SLP can also be used to install a system, minimizing the effort of searching for a suitable installation source. Find detailed information about SLP in Chapter 22, SLP Services in the Network.

17.1.3. Software Options

There are various special task areas in mobile use that are covered by dedicated software: system monitoring (especially the battery charge), data synchronization, and wireless communication with peripherals and the Internet. The following sections cover the most important applications that SUSE Linux Enterprise Server provides for each task.

17.1.3.1. System Monitoring

Two KDE system monitoring tools are provided by SUSE Linux Enterprise Server:

Power Management

Power Management is an application which lets you adjust energy saving related behavior of the KDE desktop. You can typically access it via the Battery Monitor tray icon, which changes according to the type of the current power supply. Other way to open its configuration dialog is through the Kickoff Application Launcher: Applications+Configure Desktop+Advanced+Power Management.

Click the Battery Monitor tray icon to access options to configure its behavior. You can choose one of five displayed power profiles which best fits your needs. For example, the Presentation scheme disables the screen saver and the power management in general, so that your presentation is not interrupted by system events. Click More... to open a more complex configuration screen. Here you can edit individual profiles and set advanced power management options and notifications, such as what to do when the laptop lid has been closed, or when the battery charge is low.

System Monitor

System Monitor (also called KSysguard) gathers measurable system parameters into one monitoring environment. It presents the output information in 2 tabs by default. Process Table gives detailed information about currently running processes, such as CPU load, memory usage, or process ID number and nice value. The presentation and filtering of the collected data can be customized — to add a new type of process information, left-click the process table header and choose which column to hide or add to the view. It is also possible to monitor different system parameters in various data pages or collect the data of various machines in parallel over the network. KSysguard can also run as a daemon on machines without a KDE environment. Find more information about this program in its integrated help function or in the SUSE help pages.

In the GNOME environment use Power Management Preferences and System Monitor.

17.1.3.2. Synchronizing Data

When switching between working on a mobile machine disconnected from the network and working at a networked workstation in an office, it is necessary to keep processed data synchronized across all instances. This could include e-mail folders, directories and individual files that need to be present for work on the road as well as at the office. The solution in both cases is as follows:

Synchronizing E-Mail

Use an IMAP account for storing your e-mails in the office network. Then access the e-mails from the workstation using any disconnected IMAP–enabled e-mail client, like Mozilla Thunderbird Mail, Evolution, or KMail. The e-mail client must be configured so that the same folder is always accessed for Sent messages. This ensures that all messages are available along with their status information after the synchronization process has completed. Use an SMTP server implemented in the mail client for sending messages instead of the system-wide MTA postfix or sendmail to receive reliable feedback about unsent mail.

Synchronizing Files and Directories

There are several utilities suitable for synchronizing data between a laptop and a workstation. One of the most widely used is a command-line tool called rsync. For more information, see its manual page (man 1 rsync)

17.1.3.3. Wireless Communication

As well as connecting to a home or office network with a cable, a laptop can also use wireless connection to access other computers, peripherals, cellular phones or PDAs. Linux supports three types of wireless communication:

WLAN

With the largest range of these wireless technologies, WLAN is the only one suitable for the operation of large and sometimes even spatially separate networks. Single machines can connect with each other to form an independent wireless network or access the Internet. Devices called access points act as base stations for WLAN-enabled devices and act as intermediaries for access to the Internet. A mobile user can switch among access points depending on location and which access point is offering the best connection. Like in cellular telephony, a large network is available to WLAN users without binding them to a specific location for accessing it. Find details about WLAN in Chapter 18, Wireless LAN.

Bluetooth

Bluetooth has the broadest application spectrum of all wireless technologies. It can be used for communication between computers (laptops) and PDAs or cellular phones, as can IrDA. It can also be used to connect various computers within range. Bluetooth is also used to connect wireless system components, like a keyboard or a mouse. The range of this technology is, however, not sufficient to connect remote systems to a network. WLAN is the technology of choice for communicating through physical obstacles like walls.

IrDA

IrDA is the wireless technology with the shortest range. Both communication parties must be within viewing distance of each other. Obstacles like walls cannot be overcome. One possible application of IrDA is the transmission of a file from a laptop to a cellular phone. The short path from the laptop to the cellular phone is then covered using IrDA. The long range transport of the file to the recipient of the file is handled by the mobile network. Another application of IrDA is the wireless transmission of printing jobs in the office.

17.1.4. Data Security

Ideally, you protect data on your laptop against unauthorized access in multiple ways. Possible security measures can be taken in the following areas:

Protection against Theft

Always physically secure your system against theft whenever possible. Various securing tools (like chains) are available in retail stores.

Strong Authentication

Use biometric authentication in addition to standard authentication via login and password. SUSE Linux Enterprise Server supports fingerprint authentication. For more details, see Chapter 7, Using the Fingerprint Reader (↑Security Guide).

Securing Data on the System

Important data should not only be encrypted during transmission, but also on the hard disk. This ensures its safety in case of theft. The creation of an encrypted partition with SUSE Linux Enterprise Server is described in Chapter 11, Encrypting Partitions and Files (↑Security Guide). Another possibility is to create encrypted home directories when adding the user with YaST.

[Important]Data Security and Suspend to Disk

Encrypted partitions are not unmounted during a suspend to disk event. Thus, all data on these partitions is available to any party who manages to steal the hardware and issue a resume of the hard disk.

Network Security

Any transfer of data should be secured, no matter how the transfer is done. Find general security issues regarding Linux and networks in Chapter 1, Security and Confidentiality (↑Security Guide). Security measures related to wireless networking are provided in Chapter 18, Wireless LAN.

17.2. Mobile Hardware

SUSE Linux Enterprise Server supports the automatic detection of mobile storage devices over FireWire (IEEE 1394) or USB. The term mobile storage device applies to any kind of FireWire or USB hard disk, USB flash drive, or digital camera. These devices are automatically detected and configured as soon as they are connected with the system over the corresponding interface. The file managers of both GNOME and KDE offer flexible handling of mobile hardware items. To unmount any of these media safely, use the Safely Remove (KDE) or Unmount Volume (GNOME) feature of either file manager.

External Hard Disks (USB and FireWire)

As soon as an external hard disk is correctly recognized by the system, its icon appears in the file manager. Clicking the icon displays the contents of the drive. It is possible to create folders and files here and edit or delete them. To rename a hard disk from the name it had been given by the system, select the corresponding menu item from the menu that opens when the icon is right-clicked. This name change is limited to display in the file manager. The descriptor by which the device is mounted in /media remains unaffected by this.

USB Flash Drives

These devices are handled by the system just like external hard disks. It is similarly possible to rename the entries in the file manager.

17.3. Cellular Phones and PDAs

A desktop system or a laptop can communicate with a cellular phone via Bluetooth or IrDA. Some models support both protocols and some only one of the two. The usage areas for the two protocols and the corresponding extended documentation has already been mentioned in Section 17.1.3.3, “Wireless Communication”. The configuration of these protocols on the cellular phones themselves is described in their manuals.

The support for synchronizing with handheld devices manufactured by Palm, Inc., is already built into Evolution and Kontact. Initial connection with the device is easily performed with the assistance of a wizard. Once the support for Palm Pilots is configured, it is necessary to determine which type of data should be synchronized (addresses, appointments, etc.).

17.4. For More Information

The central point of reference for all questions regarding mobile devices and Linux is http://tuxmobil.org/. Various sections of that Web site deal with the hardware and software aspects of laptops, PDAs, cellular phones and other mobile hardware.

A similar approach to that of http://tuxmobil.org/ is made by http://www.linux-on-laptops.com/. Information about laptops and handhelds can be found here.

SUSE maintains a mailing list in German dedicated to the subject of laptops. See http://lists.opensuse.org/opensuse-mobile-de/. On this list, users and developers discuss all aspects of mobile computing with SUSE Linux Enterprise Server. Postings in English are answered, but the majority of the archived information is only available in German. Use http://lists.opensuse.org/opensuse-mobile/ for English postings.

Information about OpenSync is available on http://opensync.org/.

Chapter 18. Wireless LAN

Abstract

Wireless LANs, or Wireless Local Area Network (WLANs), have become an indispensable aspect of mobile computing. Today, most laptops have built-in WLAN cards. This chapter describes how to set up a WLAN card with YaST, encrypt transmissions, and use tips and tricks.

18.1. WLAN Standards

WLAN cards communicate using the 802.11 standard, prepared by the IEEE organization. Originally, this standard provided for a maximum transmission rate of 2 Mbit/s. Meanwhile, several supplements have been added to increase the data rate. These supplements define details such as the modulation, transmission output, and transmission rates (see Table 18.1, “Overview of Various WLAN Standards”). Additionally, many companies implement hardware with proprietary or draft features.

Table 18.1. Overview of Various WLAN Standards

Name

Band (GHz)

Maximum Transmission Rate (Mbit/s)

Note

802.11 Legacy

2.4

2

Outdated; virtually no end devices available

802.11a

5

54

Less interference-prone

802.11b

2.4

11

Less common

802.11g

2.4

54

Widespread, backwards-compatible with 11b

802.11n

2.4 and/or 5

300

Common

802.11 ad

2.4/5/60

up to 7000

Released 2012, currently less common


802.11 Legacy cards are not supported by SUSE® Linux Enterprise Server. Most cards using 802.11a, 802.11b, 802.11g and 802.11n are supported. New cards usually comply with the 802.11n standard, but cards using 802.11g are still available.

18.2. Operating Modes

In wireless networking, various techniques and configurations are used to ensure fast, high-quality, and secure connections. Different operating types suit different setups. It can be difficult to choose the right authentication method. The available encryption methods have different advantages and pitfalls.

Basically, wireless networks can be classified into three network modes:

Managed Mode (Infrastructure Mode), via Access Point

Managed networks have a managing element: the access point. In this mode (also referred to as infrastructure mode), all connections of the WLAN stations in the network run through the access point, which may also serve as a connection to an ethernet. To make sure only authorized stations can connect, various authentication mechanisms (WPA, etc) are used.

Ad-hoc Mode (Peer-to-Peer Network)

Ad-hoc networks do not have an access point. The stations communicate directly with each other, therefore an ad-hoc network is usually faster than a managed network. However, the transmission range and number of participating stations are greatly limited in ad-hoc networks. They also do not support WPA authentication. If you intend to use WPA security, you should not use Ad-Hoc_Mode.

Master Mode

In master mode your network card is used as the access point. It works only if your WLAN card supports this mode. Find out the details of your WLAN card on http://linux-wless.passys.nl.

18.3. Authentication

Because a wireless network is much easier to intercept and compromise than a wired network, the various standards include authentication and encryption methods. In the original version of the IEEE 802.11 standard, these are described under the term WEP (Wired Equivalent Privacy). However, because WEP has proven to be insecure (see Section 18.6.3, “Security”), the WLAN industry (joined under the name Wi-Fi Alliance) has defined an extension called WPA, which is supposed to eliminate the weaknesses of WEP. The later IEEE 802.11i standard includes WPA and some other authentication and encryption methods. IEEE 802.11i is also referred to as WPA2, because WPA is based on a draft version of 802.11i.

To make sure that only authorized stations can connect, various authentication mechanisms are used in managed networks:

None (Open)

An open system is a system that does not require authentication. Any station can join the network. Nevertheless, WEP encryption can be used, see Section 18.4, “Encryption”.

Shared Key (according to IEEE 802.11)

In this procedure, the WEP key is used for the authentication. However, this procedure is not recommended, because it makes the WEP key more susceptible to attacks. All an attacker needs to do is to listen long enough to the communication between the station and the access point. During the authentication process, both sides exchange the same information, once in encrypted form and once in unencrypted form. This makes it possible for the key to be reconstructed with suitable tools. Because this method makes use of the WEP key for the authentication and for the encryption, it does not enhance the security of the network. A station that has the correct WEP key can authenticate, encrypt, and decrypt. A station that does not have the key cannot decrypt received packets. Accordingly, it cannot communicate, regardless of whether it had to authenticate itself.

WPA-PSK (or WPA-Personal, according to IEEE 802.1x)

WPA-PSK (PSK stands for preshared key) works similarly to the Shared Key procedure. All participating stations as well as the access point need the same key. The key is 256 bits in length and is usually entered as a passphrase. This system does not need a complex key management like WPA-EAP and is more suitable for private use. Therefore, WPA-PSK is sometimes referred to as WPA Home.

WPA-EAP (or WPA-Enterprise, according to IEEE 802.1x)

Actually, WPA-EAP (Extensible Authentication Protocol) is not an authentication system but a protocol for transporting authentication information. WPA-EAP is used to protect wireless networks in enterprises. In private networks, it is scarcely used. For this reason, WPA-EAP is sometimes referred to as WPA Enterprise.

WPA-EAP needs a Radius server to authenticate users. EAP offers three different methods for connecting and authenticating to the server:

  • Transport Layer Security (EAP-TLS): TLS authentication relies on the mutual exchange of certificates for both server and client. First, the server presents its certificate to the client where it is evaluated. If the certificate is considered valid, the client in turn presents its certificate to the server. While TLS is secure, it requires a working certification management infrastructure in your network. This infrastructure is rarely found in private networks.

  • Tunneled Transport Layer Security (EAP-TTSL)

  • Protected Extensible Authentication Protocol (EAP-PEAP): Both TTLS and PEAP are two-stage protocols. In the first stage, a secure connection is established and in the second the client authentication data is exchanged. They require far less certification management overhead than TLS, if any.

18.4. Encryption

There are various encryption methods to ensure that no unauthorized person can read the data packets that are exchanged in a wireless network or gain access to the network:

WEP (defined in IEEE 802.11)

This standard makes use of the RC4 encryption algorithm, originally with a key length of 40 bits, later also with 104 bits. Often, the length is declared as 64 bits or 128 bits, depending on whether the 24 bits of the initialization vector are included. However, this standard has some weaknesses. Attacks against the keys generated by this system may be successful. Nevertheless, it is better to use WEP than to not encrypt the network at all.

Some vendors have implemented the non-standard Dynamic WEP. It works exactly as WEP and shares the same weaknesses, except that the key is periodically changed by a key management service.

TKIP (defined in WPA/IEEE 802.11i)

This key management protocol defined in the WPA standard uses the same encryption algorithm as WEP, but eliminates its weakness. Because a new key is generated for every data packet, attacks against these keys are fruitless. TKIP is used together with WPA-PSK.

CCMP (defined in IEEE 802.11i)

CCMP describes the key management. Usually, it is used in connection with WPA-EAP, but it can also be used with WPA-PSK. The encryption takes place according to AES and is stronger than the RC4 encryption of the WEP standard.

18.5. Configuration with YaST

[Important]Security Risks in Wireless Networks

Unencrypted WLAN connections allow third parties to intercept all network data. Be sure to protect your network traffic by using one of the supported authentication and encryption methods.

Use the best possible encryption method your hardware allows. However, to use a certain encryption method, all devices in the network must support this method, otherwise they cannot communicate with each other. For example, if your router supports both WEP and WPA but the driver for your WLAN card only supports WEP, WEP is the least common denominator you can use. But even a weak encryption with WEP is better than none at all. Refer to Section 18.4, “Encryption” and Section 18.6.3, “Security” for information.

To configure a wireless LAN with YaST, you need to define the following parameters:

IP Address

Use either a static IP address or let a DHCP server dynamically assign an IP address to the interface.

Operating Mode

Defines how to integrate your machine into a WLAN, depending on the network topology. For background information, refer to Section 18.2, “Operating Modes”.

Network Name (ESSID)

Unique string identifying a network.

Authentication and Encryption Details

Depending on the authentication and encryption method your network uses, you need to enter one or more keys and/or certificates.

Several input options are available for entering the respective keys: Passphrase, ASCII (only available for WEP authentication methods), and Hexadecimal.

18.5.1. Deactivating NetworkManager

A WLAN card is usually detected during installation. If your machine is a mobile computer, NetworkManager is usually activated by default. If instead you want to configure your WLAN card with YaST, you need to deactivate NetworkManager first:

  1. Start YaST as user root.

  2. In the YaST Control Center, select Network Devices+Network Settings to open the Network Settings dialog.

    If your network is currently controlled by NetworkManager, you see a warning message that the network settings cannot be edited by YaST.

  3. To enable editing with YaST, leave the message with OK and on the Global Options tab, activate Traditional Method with ifup.

  4. For further configuration, proceed with Section 18.5.2, “Configuration for Access Points” or Section 18.5.3, “Establishing an Ad-Hoc Network”.

    Otherwise confirm your changes with OK to write the network configuration.

18.5.2. Configuration for Access Points

In this section, learn how to configure your WLAN card to connect to an (external) access point or how to use your WLAN card as access point if your WLAN card supports this. For configuration of networks without an access point, refer to Section 18.5.3, “Establishing an Ad-Hoc Network”.

Procedure 18.1. Configuring Your WLAN Card for Using an Access Point

  1. Start YaST and open the Network Settings dialog.

  2. Switch to the Overview tab where all network cards are listed that have been detected by the system. If you need more information about general network configuration, refer to Section 21.4, “Configuring a Network Connection with YaST”.

  3. Choose your wireless card from the list and click Edit to open the Network Card Setup dialog.

  4. On the Address tab, configure whether to use a dynamic or a static IP address for the machine. Usually Dynamic Address with DHCP is fine.

  5. Click Next to proceed to the Wireless Network Card Configuration dialog.

  6. To use your WLAN card to connect to an access point, set the Operating Mode to Managed.

    If however you want to use your WLAN card as access point, set the Operating Mode to Master. Note that not all WLAN cards support this mode.

    [Note]Using WPA-PSK or WPA-EAP

    If you want to use WPA-PSK or WPA-EAP authentication modes, the operating mode must be set to Managed.

  7. To connect to a certain network, enter the Network Name (ESSID). Alternatively, click Scan Network and select a network from the list of available wireless networks.

    All stations in a wireless network need the same ESSID for communicating with each other. If no ESSID is specified, your WLAN card automatically associates with the access point that has the best signal strength.

    [Note]WPA Authentication Requires an ESSID

    If you select WPA authentication, a network name (ESSID) must be set.

  8. Select an Authentication Mode for your network. Which mode is suitable, depends on your WLAN card's driver and the ability of the other devices in the network.

  9. If you have chosen to set the Authentication Mode to No Encryption, finish the configuration by clicking Next. Confirm the message about this potential security risk and leave the Overview tab (showing the newly configured WLAN card) with OK.

    If you haven chosen any of the other authentication modes, proceed with Procedure 18.2, “Entering the Encryption Details”.

Figure 18.1. YaST: Configuring the Wireless Network Card

YaST: Configuring the Wireless Network Card

Procedure 18.2. Entering the Encryption Details

The following authentication methods require an encryption key: WEP - Open, WEP - Shared Key, and WPA-PSK.

For WEP, usually only key is needed—however, up to 4 different WEP keys can be defined for your station. One of them needs to be set as the default key and is used for encryption. The others are used for decryption. Per default, a key length of 128-bit is used, but you can also choose to set the length to 64-bit.

For higher security, WPA-EAP uses a RADIUS server to authenticate users. For authentication at the server, three different methods are available: TLS, TTLS and PEAP. The credentials and certificates you need for WPA-EAP depend on the authentication method used for the RADIUS server. Ask your system administrator to provide the needed information and credentials. YaST searches for any certificate under /etc/cert. Therefore, save the certificates given to you to this location and restrict access to these files to 0600 (owner read and write).

  1. To enter the key for WEP - Open or WEP - Shared Key:

    1. Set the Key Input Type either to Passphrase, ASCII or Hexadecimal.

    2. Enter the respective Encryption Key (usually only one key is used):

      If you have selected Passphrase, enter a word or a character string from which a key is generated according to the specified key length (per default, 128-bit).

      ASCII requests an input of 5 characters for a 64-bit key and 13 characters for a 128-bit key.

      For Hexadecimal, enter 10 characters for a 64-bit key or 26 characters for a 128-bit key in hexadecimal notation.

    3. To adjust the key length to a lower bit rate (which might be necessary for older hardware), click WEP Keys and set the Key Length to 64 bit. The WEP Keys dialog also shows the WEP keys that have been entered so far. Unless another key is explicitly set as default, YaST always uses the first key as default key.

    4. To enter more keys for WEP or to modify one of the keys, select the respective entry and click Edit. Select the Key Input Type and enter the key.

    5. Confirm your changes with OK.

  2. To enter a key for WPA-PSK:

    1. Select the input method Passphrase or Hexadecimal.

    2. Enter the respective Encryption Key.

      In the Passphrase mode, the input must be 8 to 63 characters. In the Hexadecimal mode, enter 64 characters.

  3. If you have chosen WPA-EAP authentication, click Next to switch to the WPA-EAP dialog, where you enter the credentials and certificates you have been given by your network administrator.

    1. Select the EAP Mode the RADIUS server uses for authentication. The details you need to enter in the following depend on the selected EAP Mode.

    2. For TLS, provide Identity, Client Certificate, Client Key, and Client Key Password. To increase security, you can also configure a Server Certificate used to validate the server's authenticity.

      TTLS and PEAP require Identity and Password, whereas Server Certificate and Anonymous Identity are optional.

    3. To enter the advanced authentication dialog for your WPA-EAP setup, click Details.

    4. Select the Authentication Method for the second stage of EAP-TTLS or EAP-PEAP communication (inner authentication). The choice of methods depends on the authentication method for the RADIUS server you selected in the previous dialog.

    5. If the automatically-determined setting does not work for you, choose a specific PEAP Version to force the use of a certain PEAP implementation.

  4. Confirm your changes with OK. The Overview tab shows the details of your newly configured WLAN card.

  5. Click OK to finalize the configuration and to leave the dialog.

18.5.3. Establishing an Ad-Hoc Network

In some cases it is useful to connect two computers equipped with a WLAN card. To establish an ad-hoc network with YaST, do the following:

  1. Start YaST and open the Network Settings dialog.

  2. Switch to the Overview tab, choose your wireless card from the list and click Edit to open the Network Card Setup dialog.

  3. Choose Statically assigned IP Address and enter the following data:

    • IP Address: 192.168.1.1. Change this address on the second computer to 192.168.1.2, for example.

    • Subnet Mask: /24

    • Hostname: Choose any name you like.

  4. Proceed with Next.

  5. Set the Operating Mode to Ad-hoc.

  6. Choose a Network Name (ESSID). This can be any name, but it has to be used on every computer in the ad-hoc network.

  7. Select an Authentication Mode for your network. Which mode is suitable, depends on your WLAN card's driver and the ability of the other devices in the network.

  8. If you have chosen to set the Authentication Mode to No Encryption, finish the configuration by clicking Next. Confirm the message about this potential security risk and leave the Overview tab showing the newly configured WLAN card with OK.

    If you haven chosen any of the other authentication modes, proceed with Procedure 18.2, “Entering the Encryption Details”.

  9. If you do not have smpppd installed, YaST asks you to do so.

  10. Configure the other WLAN cards in the network accordingly, using the same Network Name (ESSID), the same Authentication Mode but different IP addresses.

18.5.4. Setting Additional Configuration Parameters

Usually there is no need to change the pre-configured settings when configuring your WLAN card. However, if you need detailed configuration of your WLAN connection, YaST allows you to tweak the following settings:

Channel

The specification of a channel on which the WLAN station should work. This is only needed in Ad-hoc and Master modes. In Managed mode, the card automatically searches the available channels for access points.

Bit Rate

Depending on the performance of your network, you may want to set a certain bit rate for the transmission from one point to another. In the default setting Auto, the system tries to use the highest possible data transmission rate. Some WLAN cards do not support the setting of bit rates.

Access Point

In an environment with several access points, one of them can be preselected by specifying the MAC address.

Power Management

When you are on the road, power saving technologies can help to maximize the operating time of your battery. More information about power management is available in Chapter 19, Power Management. Using power management may affect the connection quality and increase the network latency.

To access the advanced options:

  1. Start YaST and open the Network Settings dialog.

  2. Switch to the Overview tab, choose your wireless card from the list and click Edit to open the Network Card Setup dialog.

  3. Click Next to proceed to the Wireless Network Card Configuration dialog.

  4. Click Expert Settings.

  5. In Ad-hoc mode, select one of the offered channels (11 to 14, depending on your country) for the communication of your station with the other stations. In Master mode, determine on which Channel your card should offer access point functionality. The default setting for this option is Auto.

  6. Select the Bit Rate to use.

  7. Enter the MAC address of the Access Point you want to connect to.

  8. Choose if to Use Power Management or not.

  9. Confirm your changes with OK and click Next and OK to finish the configuration.

18.6. Tips and Tricks for Setting Up a WLAN

The following tools and tips can help to monitor and improve speed and stability as well as security aspects of your WLAN.

18.6.1. Utilities

The package wireless-tools contains utilities that allow to set wireless LAN specific parameters and get statistics. See http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html for more information.

18.6.2. Stability and Speed

The performance and reliability of a wireless network mainly depend on whether the participating stations receive a clear signal from the other stations. Obstructions like walls greatly weaken the signal. The more the signal strength sinks, the more the transmission slows down. During operation, check the signal strength with the iwconfig utility on the command line (Link Quality field) or with the NetworkManager applets provided by KDE or GNOME. If you have problems with the signal quality, try to set up the devices somewhere else or adjust the position of the antennas of your access points. Auxiliary antennas that substantially improve the reception are available for a number of PCMCIA WLAN cards. The rate specified by the manufacturer, such as 54 Mbit/s, is a nominal value that represents the theoretical maximum. In practice, the maximum data throughout is no more than half this value.

The iwspy command can displays WLAN statistics:

iwspy wlan0
wlan0      Statistics collected:
    00:AA:BB:CC:DD:EE : Quality:0  Signal level:0  Noise level:0
    Link/Cell/AP      : Quality:60/94  Signal level:-50 dBm   Noise level:-140 dBm (updated)
    Typical/Reference : Quality:26/94  Signal level:-60 dBm   Noise level:-90 dBm

18.6.3. Security

If you want to set up a wireless network, remember that anybody within the transmission range can easily access it if no security measures are implemented. Therefore, be sure to activate an encryption method. All WLAN cards and access points support WEP encryption. Although this is not entirely safe, it does present an obstacle for a potential attacker.

For private use, use WPA-PSK if available. Although Linux supports WPA on most hardware components, some drivers do not offer WPA support. It may also not be available on older access points and routers with WLAN functionality. For such devices, check if WPA can be implemented by means of a firmware update. If WPA is not available, WEP is better than no encryption. In enterprises with advanced security requirements, wireless networks should only be operated with WPA.

Use strong passwords for your authentication method. For example, the Web page https://www.grc.com/passwords.htm generates random 64 character passwords.

18.7. Troubleshooting

If your WLAN card fails to respond, check the following prerequisites:

  1. Do you know the device name of the WLAN card? Usually it is wlan0. Check with the tool ifconfig.

  2. Have you checked your needed firmware? Refer to /usr/share/doc/packages/wireless-tools/README.firmware for more information.

  3. Is the ESSID of your router broadcasted and visible (not hidden)?

18.7.1. Check the Network Status

The command iwconfig can give you important information about your wireless connection. For example, the following line displays the ESSID, the wireless mode, frequency, if you signal is encrypted, the link quality, and much more:

iwconfig wlan0
wlan0  IEEE 802.11abg  ESSID:"guest"
       Mode:Managed   Frequency:5.22GHz  Access Point: 00:11:22:33:44:55
       Bit Rate:54 Mb/s   Tx-Power=13 dBm
       Retry min limit:7   RTS thr:off   Fragment thr:off
       Encryption key:off
       Power Management:off
       Link Quality:62/92   Signal level:-48 dBm  Noise level:-127 dBm
       Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
       Tx excessive retries:10  Invalid misc:0   Missed beacon:0

You can also get the previous information with the iwlist command. For example, the following line displays the current bit rate:

iwlist wlan0 rate
wlan0    unknown bit-rate information.
         Current Bit Rate=54 Mb/s

If you want an overview how many access points are available, it can also be done with the iwlist command. It gives you a list of cells which looks like this:

iwlist wlan0 scanning
wlan0   Scan completed:
   Cell 01 - Address: 00:11:22:33:44:55
             Channel:40
             Frequency:5.2 GHz (Channel 40)
             Quality=67/70  Signal level=-43 dBm
             Encryption key: off
             ESSID:"Guest"
             Bit Rates: 6 Mb/s; 9 Mb/s; 12 Mb/s; 18 Mb/s; 
                        24 Mb/s; 36 Mb/s; 48 Mb/s
             Mode: Master
             Extra:tsf=0000111122223333
             Extra: Last beacon: 179ms ago
             IE: Unknown: ...

18.7.2. Multiple Network Devices

Modern laptops usually have a network card and a WLAN card. If you configured both devices with DHCP (automatic address assignment), you may encounter problems with the name resolution and the default gateway. This is evident from the fact that you can ping the router but cannot surf the Internet. The Support Database features an article on this subject at http://old-en.opensuse.org/SDB:Name_Resolution_Does_Not_Work_with_Several_Concurrent_DHCP_Clients.

18.7.3. Problems with Prism2 Cards

Several drivers are available for devices with Prism2 chips. The various cards work more or less smoothly with the various drivers. With these cards, WPA is only possible with the hostap driver. If such a card does not work properly or not at all or you want to use WPA, read /usr/share/doc/packages/wireless-tools/README.prism2.

18.8. For More Information

More information can be found on the following pages:

http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wireless.html

The Internet pages of Jean Tourrilhes, who developed the Wireless Tools for Linux, present a wealth of useful information about wireless networks.

http://tuxmobil.org

Useful hands-on information about mobile computers under Linux.

http://www.linux-on-laptops.com

More information about Linux on laptops.

Chapter 19. Power Management

►System z: The features and hardware described in this chapter do not exist on IBM System z, making this chapter irrelevant for these platforms.

Power management is especially important on laptop computers, but is also useful on other systems. ACPI (Advanced Configuration and Power Interface) is available on all modern computers (laptops, desktops, and servers). Power management technologies require suitable hardware and BIOS routines. Most laptops and many modern desktops and servers meet these requirements. It is also possible to control CPU frequency scaling to save power or decrease noise.

19.1. Power Saving Functions

Power saving functions are not only significant for the mobile use of laptops, but also for desktop systems. The main functions and their use in ACPI are:

Standby

not supported.

Suspend (to memory)

This mode writes the entire system state to the RAM. Subsequently, the entire system except the RAM is put to sleep. In this state, the computer consumes very little power. The advantage of this state is the possibility of resuming work at the same point within a few seconds without having to boot and restart applications. This function corresponds to the ACPI state S3.

Hibernation (suspend to disk)

In this operating mode, the entire system state is written to the hard disk and the system is powered off. There must be a swap partition at least as big as the RAM to write all the active data. Reactivation from this state takes about 30 to 90 seconds. The state prior to the suspend is restored. Some manufacturers offer useful hybrid variants of this mode, such as RediSafe in IBM Thinkpads. The corresponding ACPI state is S4. In Linux, suspend to disk is performed by kernel routines that are independent from ACPI.

Battery Monitor

ACPI checks the battery charge status and provides information about it. Additionally, it coordinates actions to perform when a critical charge status is reached.

Automatic Power-Off

Following a shutdown, the computer is powered off. This is especially important when an automatic shutdown is performed shortly before the battery is empty.

Processor Speed Control

In connection with the CPU, energy can be saved in three different ways: frequency and voltage scaling (also known as PowerNow! or Speedstep), throttling and putting the processor to sleep (C-states). Depending on the operating mode of the computer, these methods can also be combined.

19.2. Advanced Configuration and Power Interface (ACPI)

ACPI was designed to enable the operating system to set up and control the individual hardware components. ACPI supersedes both Power Management Plug and Play (PnP) and Advanced Power Management (APM). It delivers information about the battery, AC adapter, temperature, fan and system events, like close lid or battery low.

The BIOS provides tables containing information about the individual components and hardware access methods. The operating system uses this information for tasks like assigning interrupts or activating and deactivating components. Because the operating system executes commands stored in the BIOS, the functionality depends on the BIOS implementation. The tables ACPI can detect and load are reported in /var/log/boot.msg. See Section 19.2.2, “Troubleshooting” for more information about troubleshooting ACPI problems.

19.2.1. Controlling the CPU Performance

The CPU can save energy in three ways:

  • Frequency and Voltage Scaling

  • Throttling the Clock Frequency (T-states)

  • Putting the Processor to Sleep (C-states)

Depending on the operating mode of the computer, these methods can be combined. Saving energy also means that the system heats up less and the fans are activated less frequently.

Frequency scaling and throttling are only relevant if the processor is busy, because the most economic C-state is applied anyway when the processor is idle. If the CPU is busy, frequency scaling is the recommended power saving method. Often the processor only works with a partial load. In this case, it can be run with a lower frequency. Usually, dynamic frequency scaling controlled by the kernel on-demand governor is the best approach.

Throttling should be used as the last resort, for example, to extend the battery operation time despite a high system load. However, some systems do not run smoothly when they are throttled too much. Moreover, CPU throttling does not make sense if the CPU has little to do.

For in-depth information, refer to Chapter 11, Power Management (↑System Analysis and Tuning Guide).

19.2.2. Troubleshooting

There are two different types of problems. On one hand, the ACPI code of the kernel may contain bugs that were not detected in time. In this case, a solution will be made available for download. More often, the problems are caused by the BIOS. Sometimes, deviations from the ACPI specification are purposely integrated in the BIOS to circumvent errors in the ACPI implementation of other widespread operating systems. Hardware components that have serious errors in the ACPI implementation are recorded in a blacklist that prevents the Linux kernel from using ACPI for these components.

The first thing to do when problems are encountered is to update the BIOS. If the computer does not boot at all, one of the following boot parameters may be helpful:

pci=noacpi

Do not use ACPI for configuring the PCI devices.

acpi=ht

Only perform a simple resource configuration. Do not use ACPI for other purposes.

acpi=off

Disable ACPI.

[Warning]Problems Booting without ACPI

Some newer machines (especially SMP systems and AMD64 systems) need ACPI for configuring the hardware correctly. On these machines, disabling ACPI can cause problems.

Sometimes, the machine is confused by hardware that is attached over USB or FireWire. If a machine refuses to boot, unplug all unneeded hardware and try again.

Monitor the boot messages of the system with the command dmesg | grep -2i acpi (or all messages, because the problem may not be caused by ACPI) after booting. If an error occurs while parsing an ACPI table, the most important table—the DSDT (Differentiated System Description Table)—can be replaced with an improved version. In this case, the faulty DSDT of the BIOS is ignored. The procedure is described in Section 19.4, “Troubleshooting”.

In the kernel configuration, there is a switch for activating ACPI debug messages. If a kernel with ACPI debugging is compiled and installed, detailed information is issued.

If you experience BIOS or hardware problems, it is always advisable to contact the manufacturers. Especially if they do not always provide assistance for Linux, they should be confronted with the problems. Manufacturers will only take the issue seriously if they realize that an adequate number of their customers use Linux.

19.2.2.1. For More Information

19.3. Rest for the Hard Disk

In Linux, the hard disk can be put to sleep entirely if it is not needed or it can be run in a more economic or quieter mode. On modern laptops, you do not need to switch off the hard disks manually, because they automatically enter an economic operating mode whenever they are not needed. However, if you want to maximize power savings, test some of the following methods, using the hdparm command.

It can be used to modify various hard disk settings. The option -y instantly switches the hard disk to the standby mode. -Y puts it to sleep. hdparm -S x causes the hard disk to be spun down after a certain period of inactivity. Replace x as follows: 0 disables this mechanism, causing the hard disk to run continuously. Values from 1 to 240 are multiplied by 5 seconds. Values from 241 to 251 correspond to 1 to 11 times 30 minutes.

Internal power saving options of the hard disk can be controlled with the option -B. Select a value from 0 to 255 for maximum saving to maximum throughput. The result depends on the hard disk used and is difficult to assess. To make a hard disk quieter, use the option -M. Select a value from 128 to 254 for quiet to fast.

Often, it is not so easy to put the hard disk to sleep. In Linux, numerous processes write to the hard disk, waking it up repeatedly. Therefore, it is important to understand how Linux handles data that needs to be written to the hard disk. First, all data is buffered in the RAM. This buffer is monitored by the pdflush daemon. When the data reaches a certain age limit or when the buffer is filled to a certain degree, the buffer content is flushed to the hard disk. The buffer size is dynamic and depends on the size of the memory and the system load. By default, pdflush is set to short intervals to achieve maximum data integrity. It checks the buffer every 5 seconds and writes the data to the hard disk. The following variables are interesting:

/proc/sys/vm/dirty_writeback_centisecs

Contains the delay until a pdflush thread wakes up (in hundredths of a second).

/proc/sys/vm/dirty_expire_centisecs

Defines after which timeframe a dirty page should be written out latest. Default is 3000, which means 30 seconds.

/proc/sys/vm/dirty_background_ratio

Maximum percentage of dirty pages until pdflush begins to write them. Default is 5%.

/proc/sys/vm/dirty_ratiol

When the dirty page exceeds this percentage of the total memory, processes are forced to write dirty buffers during their time slice instead of continuing to write.

[Warning]Impairment of the Data Integrity

Changes to the pdflush daemon settings endanger the data integrity.

Apart from these processes, journaling file systems, like Btrfs, Ext3, Ext4 and others write their metadata independently from pdflush, which also prevents the hard disk from spinning down.

Another important factor is the way active programs behave. For example, good editors regularly write hidden backups of the currently modified file to the hard disk, causing the disk to wake up. Features like this can be disabled at the expense of data integrity.

In this connection, the mail daemon postfix makes use of the variable POSTFIX_LAPTOP. If this variable is set to yes, postfix accesses the hard disk far less frequently.

19.4. Troubleshooting

All error messages and alerts are logged in the file /var/log/messages. The following sections cover the most common problems.

19.4.1. ACPI Activated with Hardware Support but Functions Do Not Work

If you experience problems with ACPI, search the output of dmesg for ACPI-specific messages by using the command dmesg|grep -i acpi.

A BIOS update may be required to resolve the problem. Go to the home page of your laptop manufacturer, look for an updated BIOS version, and install it. Ask the manufacturer to comply with the latest ACPI specification. If the errors persist after the BIOS update, proceed as follows to replace the faulty DSDT table in your BIOS with an updated DSDT:

Procedure 19.1. Updating the DSDT Table in the BIOS

For the procedure below, make sure the following packages are installed: kernel-source, pmtools, and mkinitrd.

  1. Download the DSDT for your system from http://acpi.sourceforge.net/dsdt/index.php. Check if the file is decompressed and compiled as shown by the file extension .aml (ACPI machine language). If this is the case, continue with step 3.

  2. If the file extension of the downloaded table is .asl (ACPI source language) instead, compile it by executing the following command:

    iasl -sa file.asl
  3. Copy the (resulting) file DSDT.aml to any location (/etc/DSDT.aml is recommended).

  4. Edit /etc/sysconfig/kernel and adapt the path to the DSDT file accordingly.

  5. Start mkinitrd. Whenever you install the kernel and use mkinitrd to create an initrd file, the modified DSDT is integrated and loaded when the system is booted.

19.4.2. CPU Frequency Does Not Work

Refer to the kernel sources to see if your processor is supported. You may need a special kernel module or module option to activate CPU frequency control. If the kernel-source package is installed, this information is available in /usr/src/linux/Documentation/cpu-freq/*.

19.4.3. Suspend and Standby Do Not Work

ACPI systems may have problems with suspend and standby due to a faulty DSDT implementation (BIOS). If this is the case, update the BIOS.

When the system tries to unload faulty modules, the system is arrested or the suspend event is not triggered. The same can also happen if you do not unload modules or stop services that prevent a successful suspend. In both cases, try to identify the faulty module that prevented the sleep mode. The log file /var/log/pm-suspend.log contains detailed information about what is going on and where possible errors are. Modify the SUSPEND_MODULES variable in /usr/lib/pm-utils/defaults to unload problematic modules prior to a suspend or standby.

19.5. For More Information

Chapter 20. Using Tablet PCs

Abstract

SUSE® Linux Enterprise Server comes with support for Tablet PCs. In the following, learn how to install and configure your Tablet PC and discover some useful Linux* applications which accept input from digital pens.

The following Tablet PCs are supported:

  • Tablet PCs with serial and USB Wacom tablet (pen based), touch-screen or multi-touch devices.

  • Tablet PCs with FinePoint devices, such as Gateway C210X/M280E/CX2724 or HP Compaq TC1000.

  • Tablet PCs with touch screen devices, such as Asus R2H, Clevo TN120R, Fujitsu Siemens Computers P-Series, LG C1, Samsung Q1/Q1-Ultra.

After you have installed the Tablet PC packages and configured your digitizer correctly, input with the pen (also called a stylus) can be used for the following actions and applications:

  • Logging in to KDM or GDM

  • Unlocking your screen on the KDE and GNOME desktops

  • Actions that can also be triggered by other pointing devices (such as mouse or touch pad), for example, moving the cursor on the screen, starting applications, closing, resizing and moving windows, shifting window focus and dragging and dropping objects

  • Using gesture recognition in applications of the X Window System

  • Drawing with GIMP

  • Taking notes or sketching with applications like Jarnal or Xournal or editing larger amounts of text with Dasher

20.1. Installing Tablet PC Packages

The packages needed for Tablet PCs are included in the TabletPC installation pattern—if this is selected during installation, the following packages should already be installed on your system:

  • cellwriter: a character-based hardwriting input panel

  • jarnal: a Java-based note taking application

  • xournal: an application for note taking and sketching

  • xstroke: a gesture recognition program for the X Window System

  • xvkbd: a virtual keyboard for the X Window System

  • x11-input-fujitsu: the X input module for Fujitsu P-Series tablets

  • x11-input-evtouch: the X input module for some Tablet PCs with touch screens

  • xorg-x11-driver-input: the X input module for input devices, including the module for Wacom devices.

If these packages are not installed, manually install the packages you need from command line or select the TabletPC pattern for installation in YaST.

20.2. Configuring Your Tablet Device

During installation, your tablet or touch device is configured by default. If you have trouble with the configuration of your Wacom device, you use xsetwacom on the command line to change the settings.

20.3. Using the Virtual Keyboard

To log in to the KDE or GNOME desktop or to unlock the screen, you can either enter your username and password as usual or via the virtual keyboard (xvkbd) displayed below the login field. To configure the keyboard or to access the integrated help, click the xvkbd field at the left lower corner and open the xvkbd main menu.

If your input is not visible (or is not transferred to the window where you need it), redirect the focus by clicking the Focus key in xvkbd and then clicking into the window that should get the keyboard events.

Figure 20.1. xvkbd Virtual Keyboard

xvkbd Virtual Keyboard

If you want to use xvkbd after login, start it from the main menu or with xvkbd from a shell.

20.4. Rotating Your Display

Use KRandRTray (KDE) or gnome-display-properties (GNOME) to rotate or resize your display manually on the fly. Both KRandRTray and gnome-display-properties are applets for the RANDR extension of the X server.

Start KRandRTray or gnome-display-properties from the main menu, or enter krandrtray or gnome-display-properties to start the applet from a shell. After you have started the applet, the applet icon is usually added to your system tray. If the gnome-display-properties icon does not automatically appear in the system tray, make sure Show Displays in Panel is activated in the Monitor Resolution Settings dialog.

To rotate your display with KRandRTray, right-click the icon and select Configure Display. Select the desired orientation from the configuration dialog.

To rotate your display with gnome-display-properties, right-click the icon and select the desired orientation. Your display is immediately tilted to the new direction. The orientation of the graphics tablet changes also, so it can still interpret the movement of the pen correctly.

If you have problems changing the orientation of your desktop, refer to Section 20.7, “Troubleshooting” for more information.

20.5. Using Gesture Recognition

SUSE Linux Enterprise Server includes both CellWriter and xstroke for gesture recognition. Both applications accept gestures executed with the pen or other pointing devices as input for applications on the X Window System.

20.5.1. Using CellWriter

With CellWriter, you can write characters into a grid of cells—the writing is instantly recognized on a character basis. After you have finished writing, you can send the input to the currently focused application. Before you can use CellWriter for gesture recognition, the application needs to be trained to recognize your handwriting: You need to train each character of a certain map of keys (untrained characters are not activated and thus cannot be used).

Procedure 20.1. Training CellWriter

  1. Start CellWriter from the main menu or with cellwriter from the command line. On the first start, CellWriter automatically starts in the training mode. In training mode it shows a set of characters of the currently chosen key map.

  2. Enter the gesture you would like to use for a character into the respective character's cell. With the first input, the background changes its color to white, whereas the character itself is shown in light gray. Repeat the gesture multiple times until the character changes its color to black. Untrained characters are shown on a light gray or brown background (depending on the desktop's color scheme).

  3. Repeat this step until you have trained CellWriter for all characters you need.

  4. If you want to train CellWriter for another language, click the Setup button and select a language from the Languages tab. Close the configuration dialog. Click the Train button and select the key map from the drop-down box at the bottom right corner of the CellWriter window. Now repeat your training for the new map of keys.

  5. After having finished the training for the map of keys, click the Train button to switch to the normal mode.

In the normal mode, the CellWriter windows shows a couple of empty cells in which to enter the gestures. The characters are not sent to another application until you click the Enter button, so you can correct or delete characters before you use them as input. Characters that have been recognized with a low degree of confidence will appear highlighted. To correct your input, use the context menu that appears on right-clicking a cell. To delete a character, either use your pen's eraser, or middle-click with the mouse to clear the cell. After finishing your input in CellWriter, define which application should receive the input by clicking into the application's window. Then send the input to the application by clicking Enter.

Figure 20.2. Gesture Recognition with CellWriter

Gesture Recognition with CellWriter

If you click the Keys button in CellWriter, you get a virtual keyboard that can be used instead of the handwriting recognition.

To hide CellWriter, close the CellWriter window. The application now appears as icon in your system tray. To show the input window again, click the icon in the system tray.

20.5.2. Using Xstroke

With xstroke, you can use gestures with your pen or other pointing devices as input for applications on the X Window System. The xstroke alphabet is a unistroke alphabet that resembles the Graffiti* alphabet. When activated, xstroke sends the input to the currently focused window.

  1. Start xstroke from the main menu or with xstroke from a shell. This adds a pencil icon to your system tray.

  2. Start the application for which you want to create text input with the pen (for example, a terminal window, a text editor or an LibreOffice Writer).

  3. To activate the gesture recognition mode, click the pencil icon once.

  4. Perform some gestures on the graphics tablet with the pen or another pointing device. xstroke captures the gestures and transfers them to text that appears in the application window that has the focus.

  5. To switch focus to a different window, click the desired window with the pen and hold for a moment (or use the keyboard shortcut defined in your desktop's control center).

  6. To deactivate the gesture recognition mode, click the pencil icon again.

20.6. Taking Notes and Sketching with the Pen

To create drawings with the pen, you can use a professional graphics editor like GIMP or try one of the note-taking applications, Xournal or Jarnal. With both Xournal and Jarnal, you can take notes, create drawings or comment PDF files with the pen. As a Java-based application available for several platforms, Jarnal also offers basic collaboration features. For more information, refer to http://www.dklevine.com/general/software/tc1000/jarnal-net.htm. When saving your contents, Jarnal stores the data in an archive format (*.jaj) that also contains a file in SVG format.

Start Jarnal or Xournal from the main menu or by entering jarnal or xournal in a shell. To comment a PDF file in Xournal, for example, select File+Annotate PDF and open the PDF file from your file system. Use the pen or another pointing device to annotate the PDF and save your changes with File+Export to PDF.

Figure 20.3. Annotating a PDF with Xournal

Annotating a PDF with Xournal

Dasher is another useful application. It was designed for situations where keyboard input is impractical or unavailable. With a bit of training, you can rapidly enter larger amounts of text using only the pen (or other input devices—it can even be driven with an eye tracker).

Start Dasher from the main menu or with dasher from a shell. Move your pen in one direction and the application starts to zoom into the letters on the right side. From the letters passing the cross hairs in the middle, the text is created or predicted and is printed to the upper part of the window. To stop or start writing, click the display once with the pen. Modify the zooming speed at the bottom of the window.

Figure 20.4. Editing Texts with Dasher

Editing Texts with Dasher

The Dasher concept works for many languages. For more information, refer to the Dasher Web site, which offers comprehensive documentation, demonstrations and training texts. Find it at http://www.inference.phy.cam.ac.uk/dasher/

20.7. Troubleshooting

Virtual Keyboard Does Not Appear on Login Screen

Occasionally, the virtual keyboard is not displayed on the login screen. To solve this, restart the X server by pressing Ctrl+Alt+<— or press the appropriate key on your Tablet PC (if you use a slate model without integrated keyboard). If the virtual keyboard still does not show, connect an external keyboard to your slate model and log in using the hardware keyboard.

Orientation of the Wacom Graphics Tablets Does Not Change

With the xrandr command, you can change the orientation of your display from within a shell. Enter xrandr --help to view the options available. To simultaneously change the orientation of your graphics tablet, the command needs to be modified as described below:

  • For normal orientation (0° rotation):

    xrandr -o normal && xsetwacom --set "Serial Wacom Tablet" Rotate NONE
  • For 90° rotation (clockwise, portrait):

    xrandr -o right && xsetwacom --set "Serial Wacom Tablet" Rotate CW
  • For 180° rotation (landscape):

     xrandr -o inverted && xsetwacom --set "Serial Wacom Tablet" Rotate HALF
  • For 270° rotation (counterclockwise, portrait):

     xrandr -o left && xsetwacom set --"Serial Wacom Tablet" Rotate CCW

Note that the commands above depend on the output of the xsetwacom list command. Replace "Serial Wacom Tablet" with the output for the stylus or the touch device. If you have a Wacom device with touch support (you can use your fingers on the tablet to move the cursor), you need to rotate also the touch device.

20.8. For More Information

Some of the applications mentioned here do not offer integrated online help, but you can find some useful information about usage and configuration in your installed system in /usr/share/doc/package/packagename or on the Web:

Part IV. Services

Contents

21. Basic Networking
21.1. IP Addresses and Routing
21.2. IPv6—The Next Generation Internet
21.3. Name Resolution
21.4. Configuring a Network Connection with YaST
21.5. NetworkManager
21.6. Configuring a Network Connection Manually
21.7. Setting Up Bonding Devices
21.8. smpppd as Dial-up Assistant
22. SLP Services in the Network
22.1. Installation
22.2. Activating SLP
22.3. SLP Front-Ends in SUSE Linux Enterprise Server
22.4. Installation over SLP
22.5. Providing Services via SLP
22.6. For More Information
23. Time Synchronization with NTP
23.1. Configuring an NTP Client with YaST
23.2. Manually Configuring NTP in the Network
23.3. Dynamic Time Synchronization at Runtime
23.4. Setting Up a Local Reference Clock
23.5. Clock Synchronization to an External Time Reference (ETR)
24. The Domain Name System
24.1. DNS Terminology
24.2. Installation
24.3. Configuration with YaST
24.4. Starting the BIND Name Server
24.5. The /etc/named.conf Configuration File
24.6. Zone Files
24.7. Dynamic Update of Zone Data
24.8. Secure Transactions
24.9. DNS Security
24.10. For More Information
25. DHCP
25.1. Configuring a DHCP Server with YaST
25.2. DHCP Software Packages
25.3. The DHCP Server dhcpd
25.4. For More Information
26. Using NetworkManager
26.1. Use Cases for NetworkManager
26.2. Enabling or Disabling NetworkManager
26.3. Configuring Network Connections
26.4. Using KNetworkManager
26.5. Using GNOME NetworkManager Applet
26.6. NetworkManager and VPN
26.7. NetworkManager and Security
26.8. Frequently Asked Questions
26.9. Troubleshooting
26.10. For More Information
27. Samba
27.1. Terminology
27.2. Starting and Stopping Samba
27.3. Configuring a Samba Server
27.4. Configuring Clients
27.5. Samba as Login Server
27.6. Samba Server in the Network with Active Directory
27.7. For More Information
28. Sharing File Systems with NFS
28.1. Terminology
28.2. Installing NFS Server
28.3. Configuring NFS Server
28.4. Configuring Clients
28.5. For More Information
29. File Synchronization
29.1. Available Data Synchronization Software
29.2. Determining Factors for Selecting a Program
29.3. Introduction to CVS
29.4. Introduction to rsync
29.5. For More Information
30. The Apache HTTP Server
30.1. Quick Start
30.2. Configuring Apache
30.3. Starting and Stopping Apache
30.4. Installing, Activating, and Configuring Modules
30.5. Getting CGI Scripts to Work
30.6. Setting Up a Secure Web Server with SSL
30.7. Avoiding Security Problems
30.8. Troubleshooting
30.9. For More Information
31. Setting up an FTP Server with YaST
31.1. Starting the FTP Server
31.2. FTP General Settings
31.3. FTP Performance Settings
31.4. Authentication
31.5. Expert Settings
31.6. For More Information
32. The Squid Proxy Server
32.1. Some Facts about Proxy Caches
32.2. System Requirements
32.3. Starting Squid
32.4. The /etc/squid/squid.conf Configuration File
32.5. Configuring a Transparent Proxy
32.6. cachemgr.cgi
32.7. squidGuard
32.8. Cache Report Generation with Calamaris
32.9. For More Information
33. Web Based Enterprise Management Using SFCB
33.1. Introduction and Basic Concept
33.2. Setting up SFCB
33.3. SFCB CIMOM Configuration
33.4. Advanced SFCB Tasks
33.5. For More Information

Chapter 21. Basic Networking

Abstract

Linux offers the necessary networking tools and features for integration into all types of network structures. Network access using a network card, modem or other device can be configured with YaST. Manual configuration is also possible. In this chapter only the fundamental mechanisms and the relevant network configuration files are covered.

Linux and other Unix operating systems use the TCP/IP protocol. It is not a single network protocol, but a family of network protocols that offer various services. The protocols listed in Table 21.1, “Several Protocols in the TCP/IP Protocol Family”, are provided for the purpose of exchanging data between two machines via TCP/IP. Networks combined by TCP/IP, comprising a worldwide network, are also referred to as the Internet.

RFC stands for Request for Comments. RFCs are documents that describe various Internet protocols and implementation procedures for the operating system and its applications. The RFC documents describe the setup of Internet protocols. To expand your knowledge of any of the protocols, refer to the appropriate RFC documents. These are available at http://www.ietf.org/rfc.html.

Table 21.1. Several Protocols in the TCP/IP Protocol Family

Protocol

Description

TCP

Transmission Control Protocol: a connection-oriented secure protocol. The data to transmit is first sent by the application as a stream of data and converted into the appropriate format by the operating system. The data arrives at the respective application on the destination host in the original data stream format it was initially sent. TCP determines whether any data has been lost or jumbled during the transmission. TCP is implemented wherever the data sequence matters.

UDP

User Datagram Protocol: a connectionless, insecure protocol. The data to transmit is sent in the form of packets generated by the application. The order in which the data arrives at the recipient is not guaranteed and data loss is possible. UDP is suitable for record-oriented applications. It features a smaller latency period than TCP.

ICMP

Internet Control Message Protocol: Essentially, this is not a protocol for the end user, but a special control protocol that issues error reports and can control the behavior of machines participating in TCP/IP data transfer. In addition, it provides a special echo mode that can be viewed using the program ping.

IGMP

Internet Group Management Protocol: This protocol controls machine behavior when implementing IP multicast.


As shown in Figure 21.1, “Simplified Layer Model for TCP/IP”, data exchange takes place in different layers. The actual network layer is the insecure data transfer via IP (Internet protocol). On top of IP, TCP (transmission control protocol) guarantees, to a certain extent, security of the data transfer. The IP layer is supported by the underlying hardware-dependent protocol, such as ethernet.

Figure 21.1. Simplified Layer Model for TCP/IP

Simplified Layer Model for TCP/IP

The diagram provides one or two examples for each layer. The layers are ordered according to abstraction levels. The lowest layer is very close to the hardware. The uppermost layer, however, is almost a complete abstraction from the hardware. Every layer has its own special function. The special functions of each layer are mostly implicit in their description. The data link and physical layers represent the physical network used, such as ethernet.

Almost all hardware protocols work on a packet-oriented basis. The data to transmit is collected into packets (it cannot be sent all at once). The maximum size of a TCP/IP packet is approximately 64 KB. Packets are normally quite smaller, as the network hardware can be a limiting factor. The maximum size of a data packet on an ethernet is about fifteen hundred bytes. The size of a TCP/IP packet is limited to this amount when the data is sent over an ethernet. If more data is transferred, more data packets need to be sent by the operating system.

For the layers to serve their designated functions, additional information regarding each layer must be saved in the data packet. This takes place in the header of the packet. Every layer attaches a small block of data, called the protocol header, to the front of each emerging packet. A sample TCP/IP data packet traveling over an ethernet cable is illustrated in Figure 21.2, “TCP/IP Ethernet Packet”. The proof sum is located at the end of the packet, not at the beginning. This simplifies things for the network hardware.

Figure 21.2. TCP/IP Ethernet Packet

TCP/IP Ethernet Packet

When an application sends data over the network, the data passes through each layer, all implemented in the Linux kernel except the physical layer. Each layer is responsible for preparing the data so it can be passed to the next layer. The lowest layer is ultimately responsible for sending the data. The entire procedure is reversed when data is received. Like the layers of an onion, in each layer the protocol headers are removed from the transported data. Finally, the transport layer is responsible for making the data available for use by the applications at the destination. In this manner, one layer only communicates with the layer directly above or below it. For applications, it is irrelevant whether data is transmitted via a 100 Mbit/s FDDI network or via a 56-Kbit/s modem line. Likewise, it is irrelevant for the data line which kind of data is transmitted, as long as packets are in the correct format.

21.1. IP Addresses and Routing

The discussion in this section is limited to IPv4 networks. For information about IPv6 protocol, the successor to IPv4, refer to Section 21.2, “IPv6—The Next Generation Internet”.

21.1.1. IP Addresses

Every computer on the Internet has a unique 32-bit address. These 32 bits (or 4 bytes) are normally written as illustrated in the second row in Example 21.1, “Writing IP Addresses”.

Example 21.1. Writing IP Addresses

IP Address (binary):  11000000 10101000 00000000 00010100
IP Address (decimal):      192.     168.       0.      20

In decimal form, the four bytes are written in the decimal number system, separated by periods. The IP address is assigned to a host or a network interface. It can be used only once throughout the world. There are exceptions to this rule, but these are not relevant to the following passages.

The points in IP addresses indicate the hierarchical system. Until the 1990s, IP addresses were strictly categorized in classes. However, this system proved too inflexible and was discontinued. Now, classless routing (CIDR, classless interdomain routing) is used.

21.1.2. Netmasks and Routing

Netmasks are used to define the address range of a subnetwork. If two hosts are in the same subnetwork, they can reach each other directly. If they are not in the same subnetwork, they need the address of a gateway that handles all the traffic for the subnetwork. To check if two IP addresses are in the same subnet, simply AND both addresses with the netmask. If the result is identical, both IP addresses are in the same local network. If there are differences, the remote IP address, and thus the remote interface, can only be reached over a gateway.

To understand how the netmask works, look at Example 21.2, “Linking IP Addresses to the Netmask”. The netmask consists of 32 bits that identify how much of an IP address belongs to the network. All those bits that are 1 mark the corresponding bit in the IP address as belonging to the network. All bits that are 0 mark bits inside the subnetwork. This means that the more bits are 1, the smaller the subnetwork is. Because the netmask always consists of several successive 1 bits, it is also possible to just count the number of bits in the netmask. In Example 21.2, “Linking IP Addresses to the Netmask” the first net with 24 bits could also be written as 192.168.0.0/24.

Example 21.2. Linking IP Addresses to the Netmask

IP address (192.168.0.20):  11000000 10101000 00000000 00010100
Netmask   (255.255.255.0):  11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link:         11000000 10101000 00000000 00000000
In the decimal system:           192.     168.       0.       0

IP address (213.95.15.200): 11010101 10111111 00001111 11001000
Netmask    (255.255.255.0): 11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link:         11010101 10111111 00001111 00000000
In the decimal system:           213.      95.      15.       0

To give another example: all machines connected with the same ethernet cable are usually located in the same subnetwork and are directly accessible. Even when the subnet is physically divided by switches or bridges, these hosts can still be reached directly.

IP addresses outside the local subnet can only be reached if a gateway is configured for the target network. In the most common case, there is only one gateway that handles all traffic that is external. However, it is also possible to configure several gateways for different subnets.

If a gateway has been configured, all external IP packets are sent to the appropriate gateway. This gateway then attempts to forward the packets in the same manner—from host to host—until it reaches the destination host or the packet's TTL (time to live) expires.

Table 21.2. Specific Addresses

Address Type

Description

Base Network Address

This is the netmask AND any address in the network, as shown in Example 21.2, “Linking IP Addresses to the Netmask” under Result. This address cannot be assigned to any hosts.

Broadcast Address

This basically says, Access all hosts in this subnetwork. To generate this, the netmask is inverted in binary form and linked to the base network address with a logical OR. The above example therefore results in 192.168.0.255. This address cannot be assigned to any hosts.

Local Host

The address 127.0.0.1 is assigned to the loopback device on each host. A connection can be set up to your own machine with this address and with all addresses from the complete 127.0.0.0/8 loopback network as defined with IPv4. With IPv6 there is just one loopback address (::1).


Because IP addresses must be unique all over the world, you cannot just select random addresses. There are three address domains to use if you want to set up a private IP-based network. These cannot get any connection from the rest of the Internet, because they cannot be transmitted over the Internet. These address domains are specified in RFC 1597 and listed in Table 21.3, “Private IP Address Domains”.

Table 21.3. Private IP Address Domains

Network/Netmask

Domain

10.0.0.0/255.0.0.0

10.x.x.x

172.16.0.0/255.240.0.0

172.16.x.x172.31.x.x

192.168.0.0/255.255.0.0

192.168.x.x


21.2. IPv6—The Next Generation Internet

[Important]IBM System z: IPv6 Support

IPv6 is not supported by the CTC and IUCV network connections of the IBM System z hardware.

Due to the emergence of the WWW (World Wide Web), the Internet has experienced explosive growth, with an increasing number of computers communicating via TCP/IP in the past fifteen years. Since Tim Berners-Lee at CERN (http://public.web.cern.ch) invented the WWW in 1990, the number of Internet hosts has grown from a few thousand to about a hundred million.

As mentioned, an IPv4 address consists of only 32 bits. Also, quite a few IP addresses are lost—they cannot be used due to the way in which networks are organized. The number of addresses available in your subnet is two to the power of the number of bits, minus two. A subnetwork has, for example, 2, 6, or 14 addresses available. To connect 128 hosts to the Internet, for example, you need a subnetwork with 256 IP addresses, from which only 254 are usable, because two IP addresses are needed for the structure of the subnetwork itself: the broadcast and the base network address.

Under the current IPv4 protocol, DHCP or NAT (network address translation) are the typical mechanisms used to circumvent the potential address shortage. Combined with the convention to keep private and public address spaces separate, these methods can certainly mitigate the shortage. The problem with them lies in their configuration, which is a chore to set up and a burden to maintain. To set up a host in an IPv4 network, you need a number of address items, such as the host's own IP address, the subnetmask, the gateway address and maybe a name server address. All these items need to be known and cannot be derived from somewhere else.

With IPv6, both the address shortage and the complicated configuration should be a thing of the past. The following sections tell more about the improvements and benefits brought by IPv6 and about the transition from the old protocol to the new one.

21.2.1. Advantages

The most important and most visible improvement brought by the new protocol is the enormous expansion of the available address space. An IPv6 address is made up of 128 bit values instead of the traditional 32 bits. This provides for as many as several quadrillion IP addresses.

However, IPv6 addresses are not only different from their predecessors with regard to their length. They also have a different internal structure that may contain more specific information about the systems and the networks to which they belong. More details about this are found in Section 21.2.2, “Address Types and Structure”.

The following is a list of some other advantages of the new protocol:

Autoconfiguration

IPv6 makes the network plug and play capable, which means that a newly set up system integrates into the (local) network without any manual configuration. The new host uses its automatic configuration mechanism to derive its own address from the information made available by the neighboring routers, relying on a protocol called the neighbor discovery (ND) protocol. This method does not require any intervention on the administrator's part and there is no need to maintain a central server for address allocation—an additional advantage over IPv4, where automatic address allocation requires a DHCP server.

Nevertheless if a router is connected to a switch, the router should send periodic advertisments with flags telling the hosts of a network how they should interact with each other. For more information, see RFC 2462 and the radvd.conf(5) man page, and RFC 3315.

Mobility

IPv6 makes it possible to assign several addresses to one network interface at the same time. This allows users to access several networks easily, something that could be compared with the international roaming services offered by mobile phone companies: when you take your mobile phone abroad, the phone automatically logs in to a foreign service as soon as it enters the corresponding area, so you can be reached under the same number everywhere and are able to place an outgoing call just like in your home area.

Secure Communication

With IPv4, network security is an add-on function. IPv6 includes IPsec as one of its core features, allowing systems to communicate over a secure tunnel to avoid eavesdropping by outsiders on the Internet.

Backward Compatibility

Realistically, it would be impossible to switch the entire Internet from IPv4 to IPv6 at one time. Therefore, it is crucial that both protocols are able to coexist not only on the Internet, but also on one system. This is ensured by compatible addresses (IPv4 addresses can easily be translated into IPv6 addresses) and through the use of a number of tunnels. See Section 21.2.3, “Coexistence of IPv4 and IPv6”. Also, systems can rely on a dual stack IP technique to support both protocols at the same time, meaning that they have two network stacks that are completely separate, such that there is no interference between the two protocol versions.

Custom Tailored Services through Multicasting

With IPv4, some services, such as SMB, need to broadcast their packets to all hosts in the local network. IPv6 allows a much more fine-grained approach by enabling servers to address hosts through multicasting—by addressing a number of hosts as parts of a group (which is different from addressing all hosts through broadcasting or each host individually through unicasting). Which hosts are addressed as a group may depend on the concrete application. There are some predefined groups to address all name servers (the all name servers multicast group), for example, or all routers (the all routers multicast group).

21.2.2. Address Types and Structure

As mentioned, the current IP protocol is lacking in two important aspects: there is an increasing shortage of IP addresses and configuring the network and maintaining the routing tables is becoming a more complex and burdensome task. IPv6 solves the first problem by expanding the address space to 128 bits. The second one is countered by introducing a hierarchical address structure, combined with sophisticated techniques to allocate network addresses, as well as multihoming (the ability to assign several addresses to one device, giving access to several networks).

When dealing with IPv6, it is useful to know about three different types of addresses:

Unicast

Addresses of this type are associated with exactly one network interface. Packets with such an address are delivered to only one destination. Accordingly, unicast addresses are used to transfer packets to individual hosts on the local network or the Internet.

Multicast

Addresses of this type relate to a group of network interfaces. Packets with such an address are delivered to all destinations that belong to the group. Multicast addresses are mainly used by certain network services to communicate with certain groups of hosts in a well-directed manner.

Anycast

Addresses of this type are related to a group of interfaces. Packets with such an address are delivered to the member of the group that is closest to the sender, according to the principles of the underlying routing protocol. Anycast addresses are used to make it easier for hosts to find out about servers offering certain services in the given network area. All servers of the same type have the same anycast address. Whenever a host requests a service, it receives a reply from the server with the closest location, as determined by the routing protocol. If this server should fail for some reason, the protocol automatically selects the second closest server, then the third one, and so forth.

An IPv6 address is made up of eight four-digit fields, each representing 16 bits, written in hexadecimal notation. They are separated by colons (:). Any leading zero bytes within a given field may be dropped, but zeros within the field or at its end may not. Another convention is that more than four consecutive zero bytes may be collapsed into a double colon. However, only one such :: is allowed per address. This kind of shorthand notation is shown in Example 21.3, “Sample IPv6 Address”, where all three lines represent the same address.

Example 21.3. Sample IPv6 Address

fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4
fe80 :    0 :    0 :    0 :    0 : 10 : 1000 : 1a4
fe80 :                           : 10 : 1000 : 1a4

Each part of an IPv6 address has a defined function. The first bytes form the prefix and specify the type of address. The center part is the network portion of the address, but it may be unused. The end of the address forms the host part. With IPv6, the netmask is defined by indicating the length of the prefix after a slash at the end of the address. An address, as shown in Example 21.4, “IPv6 Address Specifying the Prefix Length”, contains the information that the first 64 bits form the network part of the address and the last 64 form its host part. In other words, the 64 means that the netmask is filled with 64 1-bit values from the left. Just like with IPv4, the IP address is combined with AND with the values from the netmask to determine whether the host is located in the same subnetwork or in another one.

Example 21.4. IPv6 Address Specifying the Prefix Length

fe80::10:1000:1a4/64

IPv6 knows about several predefined types of prefixes. Some of these are shown in Table 21.4, “Various IPv6 Prefixes”.

Table 21.4. Various IPv6 Prefixes

Prefix (hex)

Definition

00

IPv4 addresses and IPv4 over IPv6 compatibility addresses. These are used to maintain compatibility with IPv4. Their use still requires a router able to translate IPv6 packets into IPv4 packets. Several special addresses, such as the one for the loopback device, have this prefix as well.

2 or 3 as the first digit

Aggregatable global unicast addresses. As is the case with IPv4, an interface can be assigned to form part of a certain subnetwork. Currently, there are the following address spaces: 2001::/16 (production quality address space) and 2002::/16 (6to4 address space).

fe80::/10

Link-local addresses. Addresses with this prefix should not be routed and should therefore only be reachable from within the same subnetwork.

fec0::/10

Site-local addresses. These may be routed, but only within the network of the organization to which they belong. In effect, they are the IPv6 equivalent of the current private network address space, such as 10.x.x.x.

ff

These are multicast addresses.


A unicast address consists of three basic components:

Public Topology

The first part (which also contains one of the prefixes mentioned above) is used to route packets through the public Internet. It includes information about the company or institution that provides the Internet access.

Site Topology

The second part contains routing information about the subnetwork to which to deliver the packet.

Interface ID

The third part identifies the interface to which to deliver the packet. This also allows for the MAC to form part of the address. Given that the MAC is a globally unique, fixed identifier coded into the device by the hardware maker, the configuration procedure is substantially simplified. In fact, the first 64 address bits are consolidated to form the EUI-64 token, with the last 48 bits taken from the MAC, and the remaining 24 bits containing special information about the token type. This also makes it possible to assign an EUI-64 token to interfaces that do not have a MAC, such as those based on PPP or ISDN.

On top of this basic structure, IPv6 distinguishes between five different types of unicast addresses:

:: (unspecified)

This address is used by the host as its source address when the interface is initialized for the first time—when the address cannot yet be determined by other means.

::1 (loopback)

The address of the loopback device.

IPv4 Compatible Addresses

The IPv6 address is formed by the IPv4 address and a prefix consisting of 96 zero bits. This type of compatibility address is used for tunneling (see Section 21.2.3, “Coexistence of IPv4 and IPv6”) to allow IPv4 and IPv6 hosts to communicate with others operating in a pure IPv4 environment.

IPv4 Addresses Mapped to IPv6

This type of address specifies a pure IPv4 address in IPv6 notation.

Local Addresses

There are two address types for local use:

link-local

This type of address can only be used in the local subnetwork. Packets with a source or target address of this type should not be routed to the Internet or other subnetworks. These addresses contain a special prefix (fe80::/10) and the interface ID of the network card, with the middle part consisting of zero bytes. Addresses of this type are used during automatic configuration to communicate with other hosts belonging to the same subnetwork.

site-local

Packets with this type of address may be routed to other subnetworks, but not to the wider Internet—they must remain inside the organization's own network. Such addresses are used for intranets and are an equivalent of the private address space defined by IPv4. They contain a special prefix (fec0::/10), the interface ID, and a 16 bit field specifying the subnetwork ID. Again, the rest is filled with zero bytes.

As a completely new feature introduced with IPv6, each network interface normally gets several IP addresses, with the advantage that several networks can be accessed through the same interface. One of these networks can be configured completely automatically using the MAC and a known prefix with the result that all hosts on the local network can be reached as soon as IPv6 is enabled (using the link-local address). With the MAC forming part of it, any IP address used in the world is unique. The only variable parts of the address are those specifying the site topology and the public topology, depending on the actual network in which the host is currently operating.

For a host to go back and forth between different networks, it needs at least two addresses. One of them, the home address, not only contains the interface ID but also an identifier of the home network to which it normally belongs (and the corresponding prefix). The home address is a static address and, as such, it does not normally change. Still, all packets destined to the mobile host can be delivered to it, regardless of whether it operates in the home network or somewhere outside. This is made possible by the completely new features introduced with IPv6, such as stateless autoconfiguration and neighbor discovery. In addition to its home address, a mobile host gets one or more additional addresses that belong to the foreign networks where it is roaming. These are called care-of addresses. The home network has a facility that forwards any packets destined to the host when it is roaming outside. In an IPv6 environment, this task is performed by the home agent, which takes all packets destined to the home address and relays them through a tunnel. On the other hand, those packets destined to the care-of address are directly transferred to the mobile host without any special detours.

21.2.3. Coexistence of IPv4 and IPv6

The migration of all hosts connected to the Internet from IPv4 to IPv6 is a gradual process. Both protocols will coexist for some time to come. The coexistence on one system is guaranteed where there is a dual stack implementation of both protocols. That still leaves the question of how an IPv6 enabled host should communicate with an IPv4 host and how IPv6 packets should be transported by the current networks, which are predominantly IPv4 based. The best solutions offer tunneling and compatibility addresses (see Section 21.2.2, “Address Types and Structure”).

IPv6 hosts that are more or less isolated in the (worldwide) IPv4 network can communicate through tunnels: IPv6 packets are encapsulated as IPv4 packets to move them across an IPv4 network. Such a connection between two IPv4 hosts is called a tunnel. To achieve this, packets must include the IPv6 destination address (or the corresponding prefix) as well as the IPv4 address of the remote host at the receiving end of the tunnel. A basic tunnel can be configured manually according to an agreement between the hosts' administrators. This is also called static tunneling.

However, the configuration and maintenance of static tunnels is often too labor-intensive to use them for daily communication needs. Therefore, IPv6 provides for three different methods of dynamic tunneling:

6over4

IPv6 packets are automatically encapsulated as IPv4 packets and sent over an IPv4 network capable of multicasting. IPv6 is tricked into seeing the whole network (Internet) as a huge local area network (LAN). This makes it possible to determine the receiving end of the IPv4 tunnel automatically. However, this method does not scale very well and is also hampered by the fact that IP multicasting is far from widespread on the Internet. Therefore, it only provides a solution for smaller corporate or institutional networks where multicasting can be enabled. The specifications for this method are laid down in RFC 2529.

6to4

With this method, IPv4 addresses are automatically generated from IPv6 addresses, enabling isolated IPv6 hosts to communicate over an IPv4 network. However, a number of problems have been reported regarding the communication between those isolated IPv6 hosts and the Internet. The method is described in RFC 3056.

IPv6 Tunnel Broker

This method relies on special servers that provide dedicated tunnels for IPv6 hosts. It is described in RFC 3053.

21.2.4. Configuring IPv6

To configure IPv6, you normally do not need to make any changes on the individual workstations. IPv6 is enabled by default. You can disable it during installation in the network configuration step described in Section “Network Configuration” (Chapter 6, Installation with YaST, ↑Deployment Guide). To disable or enable IPv6 on an installed system, use the YaST Network Settings module. On the Global Options tab, check or uncheck the Enable IPv6 option as necessary. If you want to enable it temporarily until the next reboot, enter modprobe -i ipv6 as root. It is basically impossible to unload the ipv6 module once loaded.

Because of the autoconfiguration concept of IPv6, the network card is assigned an address in the link-local network. Normally, no routing table management takes place on a workstation. The network routers can be queried by the workstation, using the router advertisement protocol, for what prefix and gateways should be implemented. The radvd program can be used to set up an IPv6 router. This program informs the workstations which prefix to use for the IPv6 addresses and which routers. Alternatively, use zebra/quagga for automatic configuration of both addresses and routing.

Consult the ifcfg-tunnel (5) man page to get information about how to set up various types of tunnels using the /etc/sysconfig/network files.

21.2.5. For More Information

The above overview does not cover the topic of IPv6 comprehensively. For a more in-depth look at the new protocol, refer to the following online documentation and books:

http://www.ipv6.org/

The starting point for everything about IPv6.

http://www.ipv6day.org

All information needed to start your own IPv6 network.

http://www.ipv6-to-standard.org/

The list of IPv6-enabled products.

http://www.bieringer.de/linux/IPv6/

Here, find the Linux IPv6-HOWTO and many links related to the topic.

RFC 2640

The fundamental RFC about IPv6.

IPv6 Essentials

A book describing all the important aspects of the topic is IPv6 Essentials by Silvia Hagen (ISBN 0-596-00125-8).

21.3. Name Resolution

DNS assists in assigning an IP address to one or more names and assigning a name to an IP address. In Linux, this conversion is usually carried out by a special type of software known as bind. The machine that takes care of this conversion is called a name server. The names make up a hierarchical system in which each name component is separated by a period. The name hierarchy is, however, independent of the IP address hierarchy described above.

Consider a complete name, such as jupiter.example.com, written in the format hostname.domain. A full name, referred to as a fully qualified domain name (FQDN), consists of a hostname and a domain name (example.com). The latter also includes the top level domain or TLD (com).

TLD assignment has become quite confusing for historical reasons. Traditionally, three-letter domain names are used in the USA. In the rest of the world, the two-letter ISO national codes are the standard. In addition to that, longer TLDs were introduced in 2000 that represent certain spheres of activity (for example, .info, .name, .museum).

In the early days of the Internet (before 1990), the file /etc/hosts was used to store the names of all the machines represented over the Internet. This quickly proved to be impractical in the face of the rapidly growing number of computers connected to the Internet. For this reason, a decentralized database was developed to store the hostnames in a widely distributed manner. This database, similar to the name server, does not have the data pertaining to all hosts in the Internet readily available, but can dispatch requests to other name servers.

The top of the hierarchy is occupied by root name servers. These root name servers manage the top level domains and are run by the Network Information Center (NIC). Each root name server knows about the name servers responsible for a given top level domain. Information about top level domain NICs is available at http://www.internic.net.

DNS can do more than just resolve hostnames. The name server also knows which host is receiving e-mails for an entire domain—the mail exchanger (MX).

For your machine to resolve an IP address, it must know about at least one name server and its IP address. Easily specify such a name server with the help of YaST. If you have a modem dial-up connection, you may not need to configure a name server manually at all. The dial-up protocol provides the name server address as the connection is made. The configuration of name server access with SUSE® Linux Enterprise Server is described in Section 21.4.1.4, “Configuring Hostname and DNS”. Setting up your own name server is described in Chapter 24, The Domain Name System.

The protocol whois is closely related to DNS. With this program, quickly find out who is responsible for any given domain.

[Note]MDNS and .local Domain Names

The .local top level domain is treated as link-local domain by the resolver. DNS requests are send as multicast DNS requests instead of normal DNS requests. If you already use the .local domain in your name server configuration, you must switch this option off in /etc/host.conf. For more information, see the host.conf manual page.

If you want to switch off MDNS during installation, use nomdns=1 as a boot parameter.

For more information on multicast DNS, see http://www.multicastdns.org.

21.4. Configuring a Network Connection with YaST

There are many supported networking types on Linux. Most of them use different device names and the configuration files are spread over several locations in the file system. For a detailed overview of the aspects of manual network configuration, see Section 21.6, “Configuring a Network Connection Manually”.

On SUSE Linux Enterprise Desktop, where NetworkManager is active by default, all network cards are configured. If NetworkManager is not active, only the first interface with link up (with a network cable connected) is automatically configured. Additional hardware can be configured any time on the installed system. The following sections describe the network configuration for all types of network connections supported by SUSE Linux Enterprise Server.

[Tip]IBM System z: Hotpluggable Network Cards

On IBM System z platforms, hotpluggable network cards are supported, but not their automatic network integration via DHCP (as is the case on the PC). After detection, manually configure the interface.

21.4.1. Configuring the Network Card with YaST

To configure your wired or wireless network card in YaST, select Network Devices+Network Settings. After starting the module, YaST displays the Network Settings dialog with four tabs: Global Options, Overview, Hostname/DNS and Routing.

The Global Options tab allows you to set general networking options such as the use of NetworkManager, IPv6 and general DHCP options. For more information, see Section 21.4.1.1, “Configuring Global Networking Options”.

The Overview tab contains information about installed network interfaces and configurations. Any properly detected network card is listed with its name. You can manually configure new cards, remove or change their configuration in this dialog. If you want to manually configure a card that was not automatically detected, see Section 21.4.1.3, “Configuring an Undetected Network Card”. If you want to change the configuration of an already configured card, see Section 21.4.1.2, “Changing the Configuration of a Network Card”.

The Hostname/DNS tab allows to set the hostname of the machine and name the servers to be used. For more information, see Section 21.4.1.4, “Configuring Hostname and DNS”.

The Routing tab is used for the configuration of routing. See Section 21.4.1.5, “Configuring Routing” for more information.

Figure 21.3. Configuring Network Settings

Configuring Network Settings

21.4.1.1. Configuring Global Networking Options

The Global Options tab of the YaST Network Settings module allows you to set important global networking options, such as the use of NetworkManager, IPv6 and DHCP client options. These settings are applicable for all network interfaces.

In the Network Setup Method choose the way network connections are managed. If you want a NetworkManager desktop applet to manage connections for all interfaces, choose User Controlled with NetworkManager. This option is well suited for switching between multiple wired and wireless networks. If you do not run a desktop environment (GNOME or KDE), or if your computer is a Xen server, virtual system, or provides network services such as DHCP or DNS in your network, use the Traditional Method with ifup. If NetworkManager is used, nm-applet should be used to configure network options and the Overview, Hostname/DNS and Routing tabs of the Network Settings module are disabled. For more information on NetworkManager, see Chapter 26, Using NetworkManager.

In the IPv6 Protocol Settings choose whether you want to use the IPv6 protocol. It is possible to use IPv6 together with IPv4. By default, IPv6 is activated. However, in networks not using IPv6 protocol, response times can be faster with IPv6 protocol disabled. If you want to disable IPv6, uncheck the Enable IPv6 option. This disables autoload of the kernel module for IPv6. This will be applied after reboot.

In the DHCP Client Options configure options for the DHCP client. If you want the DHCP client to ask the server to always broadcast its responses, check Request Broadcast Response. It may be needed if your machine is moving between different networks. The DHCP Client Identifier must be different for each DHCP client on a single network. If left empty, it defaults to the hardware address of the network interface. However, if you are running several virtual machines using the same network interface and, therefore, the same hardware address, specify a unique free-form identifier here.

The Hostname to Send specifies a string used for the hostname option field when dhcpcd sends messages to DHCP server. Some DHCP servers update name server zones (forward and reverse records) according to this hostname (Dynamic DNS). Also, some DHCP servers require the Hostname to Send option field to contain a specific string in the DHCP messages from clients. Leave AUTO to send the current hostname (that is the one defined in /etc/HOSTNAME). Leave the option field empty for not sending any hostname. If yo do not want to change the default route according to the information from DHCP, uncheck Change Default Route via DHCP.

21.4.1.2. Changing the Configuration of a Network Card

To change the configuration of a network card, select a card from the list of the detected cards in Network Settings+Overview in YaST and click Edit. The Network Card Setup dialog appears in which to adjust the card configuration using the General, Address and Hardware tabs. For information about wireless card configuration, see Section 18.5, “Configuration with YaST”.

21.4.1.2.1. Configuring IP Addresses

You can set the IP address of the network card or the way its IP address is determined in the Address tab of the Network Card Setup dialog. Both IPv4 and IPv6 addresses are supported. The network card can have No IP Address (which is useful for bonding devices), a Statically Assigned IP Address (IPv4 or IPv6) or a Dynamic Address assigned via DHCP or Zeroconf or both.

If using Dynamic Address, select whether to use DHCP Version 4 Only (for IPv4), DHCP Version 6 Only (for IPv6) or DHCP Both Version 4 and 6.

If possible, the first network card with link that is available during the installation is automatically configured to use automatic address setup via DHCP. On SUSE Linux Enterprise Desktop, where NetworkManager is active by default, all network cards are configured.

[Note]IBM System z and DHCP

On IBM System z platforms, DHCP-based address configuration is only supported with network cards that have a MAC address. This is only the case with OSA and OSA Express cards.

DHCP should also be used if you are using a DSL line but with no static IP assigned by the ISP (Internet Service Provider). If you decide to use DHCP, configure the details in DHCP Client Options in the Global Options tab of the Network Settings dialog of the YaST network card configuration module. Specify whether the DHCP client should ask the server to always broadcast its responses in Request Broadcast Response. This option may be needed if your machine is a mobile client moving between networks. If you have a virtual host setup where different hosts communicate through the same interface, an DHCP Client Identifier is necessary to distinguish them.

DHCP is a good choice for client configuration but it is not ideal for server configuration. To set a static IP address, proceed as follows:

  1. Select a card from the list of detected cards in the Overview tab of the YaST network card configuration module and click Edit.

  2. In the Address tab, choose Statically Assigned IP Address.

  3. Enter the IP Address. Both IPv4 and IPv6 addresses can be used. Enter the network mask in Subnet Mask. If the IPv6 address is used, use Subnet Mask for prefix length in format /64.

    Optionally, you can enter a fully qualified Hostname for this address, which will be written to the /etc/hosts configuration file.

  4. Click Next.

  5. To activate the configuration, click OK.

If you use the static address, the name servers and default gateway are not configured automatically. To configure name servers, proceed as described in Section 21.4.1.4, “Configuring Hostname and DNS”. To configure a gateway, proceed as described in Section 21.4.1.5, “Configuring Routing”.

21.4.1.2.2. Configuring Aliases

One network device can have multiple IP addresses, called aliases.

[Note]Aliases Are a Compatibility Feature

These so-called aliases resp. labels work with IPv4 only. With IPv6 they will be ignored. Using iproute2 network interfaces can have one or more addresses.

Using YaST to set an alias for your network card, proceed as follows:

  1. Select a card from the list of detected cards in the Overview tab of the YaST network card configuration module and click Edit.

  2. In the Address+Additional Addresses tab, click Add.

  3. Enter Alias Name, IP Address, and Netmask. Do not include the interface name in the alias name.

  4. Click OK.

  5. Click Next.

  6. To activate the configuration, click OK.

21.4.1.2.3. Changing the Device Name and Udev Rules

It is possible to change the device name of the network card when it is used. It is also possible to determine whether the network card should be identified by udev via its hardware (MAC) address or via the bus ID. The later option is preferable in large servers to ease hot swapping of cards. To set these options with YaST, proceed as follows:

  1. Select a card from the list of detected cards in the Overview tab of the YaST Network Settings module and click Edit.

  2. Go to the Hardware tab. The current device name is shown in Udev Rules. Click Change.

  3. Select whether udev should identify the card by its MAC Address or Bus ID. The current MAC address and bus ID of the card are shown in the dialog.

  4. To change the device name, check the Change Device Name option and edit the name.

  5. Click OK and Next.

  6. To activate the configuration, click OK.

21.4.1.2.4. Changing Network Card Kernel Driver

For some network cards, several kernel drivers may be available. If the card is already configured, YaST allows you to select a kernel driver to be used from a list of available suitable drivers. It is also possible to specify options for the kernel driver. To set these options with YaST, proceed as follows:

  1. Select a card from the list of detected cards in the Overview tab of the YaST Network Settings module and click Edit.

  2. Go to the Hardware tab.

  3. Select the kernel driver to be used in Module Name. Enter any options for the selected driver in Options in the form option=value . If more options are used, they should be space-separated.

  4. Click OK and Next.

  5. To activate the configuration, click OK.

21.4.1.2.5. Activating the Network Device

If you use the traditional method with ifup, you can configure your device to either start during boot, on cable connection, on card detection, manually or never. To change device start-up, proceed as follows:

  1. In YaST select a card from the list of detected cards in Network Devices+Network Settings and click Edit.

  2. In the General tab, select the desired entry from Device Activation.

    Choose At Boot Time to start the device during the system boot. With On Cable Connection, the interface is watched for any existing physical connection. With On Hotplug, the interface is set as soon as available. It is similar to the At Boot Time option, and only differs in the fact that no error occurs if the interface is not present at boot time. Choose Manually to control the interface manually with ifup. Choose Never to not start the device at all. The On NFSroot is similar to At Boot Time, but the interface does not shut down with the rcnetwork stop command. Use this if you use an nfs or iscsi root file system.

  3. Click Next.

  4. To activate the configuration, click OK.

Usually, only the system administrator can activate and deactivate network interfaces. If you want any user to be able to activate this interface via KInternet, select Enable Device Control for Non-root User via KInternet.

21.4.1.2.6. Setting Up Maximum Transfer Unit Size

You can set a maximum transmission unit (MTU) for the interface. MTU refers to the largest allowed packet size in bytes. A higher MTU brings higher bandwidth efficiency. However, large packets can block up a slow interface for some time, increasing the lag for further packets.

  1. In YaST select a card from the list of detected cards in Network Devices+Network Settings and click Edit.

  2. In the General tab, select the desired entry from the Set MTU list.

  3. Click Next.

  4. To activate the configuration, click OK.

21.4.1.2.7. Configuring the Firewall

Without having to enter the detailed firewall setup as described in Section “Configuring the Firewall with YaST” (Chapter 15, Masquerading and Firewalls, ↑Security Guide), you can determine the basic firewall setup for your device as part of the device setup. Proceed as follows:

  1. Open the YaST Network Devices+Network Settings module. In the Overview tab, select a card from the list of detected cards and click Edit.

  2. Enter the General tab of the Network Settings dialog.

  3. Determine the firewall zone to which your interface should be assigned. The following options are available:

    Firewall Disabled

    This option is available only if the firewall is disabled and the firewall does not run at all. Only use this option if your machine is part of a greater network that is protected by an outer firewall.

    Automatically Assign Zone

    This option is available only if the firewall is enabled. The firewall is running and the interface is automatically assigned to a firewall zone. The zone which contains the keyword any or the external zone will be used for such an interface.

    Internal Zone (Unprotected)

    The firewall is running, but does not enforce any rules to protect this interface. Use this option if your machine is part of a greater network that is protected by an outer firewall. It is also useful for the interfaces connected to the internal network, when the machine has more network interfaces.

    Demilitarized Zone

    A demilitarized zone is an additional line of defense in front of an internal network and the (hostile) Internet. Hosts assigned to this zone can be reached from the internal network and from the Internet, but cannot access the internal network.

    External Zone

    The firewall is running on this interface and fully protects it against other—presumably hostile—network traffic. This is the default option.

  4. Click Next.

  5. Activate the configuration by clicking OK.

21.4.1.3. Configuring an Undetected Network Card

Your card may not be detected correctly. In this case, the card is not included in the list of detected cards. If you are sure that your system includes a driver for your card, you can configure it manually. You can also configure special network device types, such as bridge, bond, TUN or TAP. To configure an undetected network card (or a special device) proceed as follows:

  1. In the Network Devices+Network Settings+Overview dialog in YaST click Add.

  2. In the Hardware dialog, set the Device Type of the interface from the available options and Configuration Name. If the network card is a PCMCIA or USB device, activate the respective check box and exit this dialog with Next. Otherwise, you can define the kernel Module Name to be used for the card and its Options, if necessary.

    In Ethtool Options, you can set ethtool options used by ifup for the interface. See the ethtool manual page for available options. If the option string starts with a - (for example -K interface_name rx on), the second word in the string is replaced with the current interface name. Otherwise (for example autoneg off speed 10) ifup prepends -s interface_name.

  3. Click Next.

  4. Configure any needed options, such as the IP address, device activation or firewall zone for the interface in the General, Address, and Hardware tabs. For more information about the configuration options, see Section 21.4.1.2, “Changing the Configuration of a Network Card”.

  5. If you selected Wireless as the device type of the interface, configure the wireless connection in the next dialog. Detailed information about wireless device configuration is available in Chapter 18, Wireless LAN.

  6. Click Next.

  7. To activate the new network configuration, click OK.

21.4.1.4. Configuring Hostname and DNS

If you did not change the network configuration during installation and the wired card was already available, a hostname was automatically generated for your computer and DHCP was activated. The same applies to the name service information your host needs to integrate into a network environment. If DHCP is used for network address setup, the list of domain name servers is automatically filled with the appropriate data. If a static setup is preferred, set these values manually.

To change the name of your computer and adjust the name server search list, proceed as follows:

  1. Go to the Network Settings+Hostname/DNS tab in the Network Devices module in YaST.

  2. Enter the Hostname and, if needed, the Domain Name. The domain is especially important if the machine is a mail server. Note that the hostname is global and applies to all set network interfaces.

    If you are using DHCP to get an IP address, the hostname of your computer will be automatically set by the DHCP. You may want to disable this behavior if you connect to different networks, because they may assign different hostnames and changing the hostname at runtime may confuse the graphical desktop. To disable using DHCP to get an IP address uncheck Change Hostname via DHCP.

    Assign Hostname to Loopback IP associates your hostname with 127.0.0.2 (loopback) IP address in /etc/hosts. This is an useful option if you want to have the hostname resolvable at all times, even without active network.

  3. In Modify DNS Configuration, select the way the DNS configuration (name servers, search list, the content of the /etc/resolv.conf file) is modified.

    If the Use Default Policy option is selected, the configuration is handled by the netconfig script which merges the data defined statically (with YaST or in the configuration files) with data obtained dynamically (from the DHCP client or NetworkManager). This default policy is sufficient in most cases.

    If the Only Manually option is selected, netconfig is not allowed to modify the /etc/resolv.conf file. However, this file can be edited manually.

    If the Custom Policy option is selected, a Custom Policy Rule string defining the merge policy should be specified. The string consists of a comma-separated list of interface names to be considered a valid source of settings. Except for complete interface names, basic wild cards to match multiple interfaces are allowed, as well. For example, eth* ppp? will first target all eth and then all ppp0-ppp9 interfaces. There are two special policy values that indicate how to apply the static settings defined in the /etc/sysconfig/network/config file:

    STATIC

    The static settings have to be merged together with the dynamic settings.

    STATIC_FALLBACK

    The static settings are used only when no dynamic configuration is available.

    For more information, see the man 8 netconfig.

  4. Enter the Name Servers and fill in the Domain Search list. Name servers must be specified by IP addresses, such as 192.168.1.116, not by hostnames. Names specified in the Domain Search tab are domain names used for resolving hostnames without a specified domain. If more than one Domain Search is used, separate domains with commas or white space.

  5. To activate the configuration, click OK.

It is also possible to edit the hostname using YaST from the command line. The changes made by YaST take effect immediately (which is not the case when editing the /etc/HOSTNAME file manually). To change the hostname, use the following command:

yast dns edit hostname=hostname

To change the name servers, use the following commands:

yast dns edit nameserver1=192.168.1.116
yast dns edit nameserver2=192.168.1.116
yast dns edit nameserver3=192.168.1.116

21.4.1.5. Configuring Routing

To make your machine communicate with other machines and other networks, routing information must be given to make network traffic take the correct path. If DHCP is used, this information is automatically provided. If a static setup is used, this data must be added manually.

  1. In YaST go to Network Settings+Routing.

  2. Enter the IP address of the Default Gateway (IPv4 and IPv6 if necessary). The default gateway matches every possible destination, but if any other entry exists that matches the required address, use this instead of the default route.

  3. More entries can be entered in the Routing Table. Enter the Destination network IP address, Gateway IP address and the Netmask. Select the Device through which the traffic to the defined network will be routed (the minus sign stands for any device). To omit any of these values, use the minus sign -. To enter a default gateway into the table, use default in the Destination field.

    [Note]

    If more default routes are used, it is possible to specify the metric option to determine which route has a higher priority. To specify the metric option, enter - metric number in Options. The route with the highest metric is used as default. If the network device is disconnected, its route will be removed and the next one will be used. However, the current kernel does not use metric in static routing, only routing daemons like multipathd do.

  4. If the system is a router, enable the IP Forwarding option in the Network Settings.

  5. To activate the configuration, click OK.

21.4.2. Modem

[Tip]IBM System z: Modem

The configuration of this type of hardware is not supported on IBM System z platforms.

In the YaST Control Center, access the modem configuration under Network Devices+Modem. If your modem was not automatically detected, go to the Modem Devices tab and open the dialog for manual configuration by clicking Add. Enter the interface to which the modem is connected under Modem Device.

[Tip]CDMA and GPRS Modems

Configure supported CDMA and GPRS modems with the YaST Modem module just as you would configure regular modems.

Figure 21.4. Modem Configuration

Modem Configuration

If you are behind a private branch exchange (PBX), you may need to enter a dial prefix. This is often a zero. Consult the instructions that came with the PBX to find out. Also select whether to use tone or pulse dialing, whether the speaker should be on and whether the modem should wait until it detects a dial tone. The last option should not be enabled if the modem is connected to an exchange.

Under Details, set the baud rate and the modem initialization strings. Only change these settings if your modem was not detected automatically or if it requires special settings for data transmission to work. This is mainly the case with ISDN terminal adapters. Leave this dialog by clicking OK. To delegate control over the modem to the normal user without root permissions, activate Enable Device Control for Non-root User via KInternet. In this way, a user without administrator permissions can activate or deactivate an interface. Under Dial Prefix Regular Expression, specify a regular expression. The Dial Prefix in KInternet, which can be modified by the normal user, must match this regular expression. If this field is left empty, the user cannot set a different Dial Prefix without administrator permissions.

In the next dialog, select the ISP. To choose from a predefined list of ISPs operating in your country, select Country. Alternatively, click New to open a dialog in which to provide the data for your ISP. This includes a name for the dial-up connection and ISP as well as the login and password provided by your ISP. Enable Always Ask for Password to be prompted for the password each time you connect.

In the last dialog, specify additional connection options:

Dial on Demand

If you enable Dial on Demand, set at least one name server. Use this feature only if your Internet connection is inexpensive, because there are programs that periodically request data from the Internet.

Modify DNS when Connected

This option is enabled by default, with the effect that the name server address is updated each time you connect to the Internet.

Automatically Retrieve DNS

If the provider does not transmit its domain name server after connecting, disable this option and enter the DNS data manually.

Automatically Reconnect

If this options is enabled, the connection is automatically reestablished after failure.

Ignore Prompts

This option disables the detection of any prompts from the dial-up server. If the connection build-up is slow or does not work at all, try this option.

External Firewall Interface

Selecting this option activates the firewall and sets the interface as external. This way, you are protected from outside attacks for the duration of your Internet connection.

Idle Time-Out (seconds)

With this option, specify a period of network inactivity after which the modem disconnects automatically.

IP Details

This opens the address configuration dialog. If your ISP does not assign a dynamic IP address to your host, disable Dynamic IP Address then enter your host's local IP address and the remote IP address. Ask your ISP for this information. Leave Default Route enabled and close the dialog by selecting OK.

Selecting Next returns to the original dialog, which displays a summary of the modem configuration. Close this dialog with OK.

21.4.3. ISDN

[Tip]IBM System z: ISDN

The configuration of this type of hardware is not supported on IBM System z platforms.

Use this module to configure one or several ISDN cards for your system. If YaST did not detect your ISDN card, click on Add in the ISDN Devices tab and manually select your card. Multiple interfaces are possible, but several ISPs can be configured for one interface. In the subsequent dialogs, set the ISDN options necessary for the proper functioning of the card.

Figure 21.5. ISDN Configuration

ISDN Configuration

In the next dialog, shown in Figure 21.5, “ISDN Configuration”, select the protocol to use. The default is Euro-ISDN (EDSS1), but for older or larger exchanges, select 1TR6. If you are in the US, select NI1. Select your country in the relevant field. The corresponding country code then appears in the field next to it. Finally, provide your Area Code and the Dial Prefix if necessary. If you do not want to log all your ISDN traffic, uncheck the Start ISDN Log option.

Activate Device defines how the ISDN interface should be started: At Boot Time causes the ISDN driver to be initialized each time the system boots. Manually requires you to load the ISDN driver as root with the command rcisdn start. On Hotplug, used for PCMCIA or USB devices, loads the driver after the device is plugged in. When finished with these settings, select OK.

In the next dialog, specify the interface type for your ISDN card and add ISPs to an existing interface. Interfaces may be either the SyncPPP or the RawIP type, but most ISPs operate in the SyncPPP mode, which is described below.

Figure 21.6. ISDN Interface Configuration

ISDN Interface Configuration

The number to enter for My Phone Number depends on your particular setup:

ISDN Card Directly Connected to Phone Outlet

A standard ISDN line provides three phone numbers (called multiple subscriber numbers, or MSNs). If the subscriber asked for more, there may be up to 10. One of these MSNs must be entered here, but without your area code. If you enter the wrong number, your phone operator automatically falls back to the first MSN assigned to your ISDN line.

ISDN Card Connected to a Private Branch Exchange

Again, the configuration may vary depending on the equipment installed:

  1. Smaller private branch exchanges (PBX) built for home purposes mostly use the Euro-ISDN (EDSS1) protocol for internal calls. These exchanges have an internal S0 bus and use internal numbers for the equipment connected to them.

    Use one of the internal numbers as your MSN. You should be able to use at least one of the exchange's MSNs that have been enabled for direct outward dialing. If this does not work, try a single zero. For further information, consult the documentation delivered with your phone exchange.

  2. Larger phone exchanges designed for businesses normally use the 1TR6 protocol for internal calls. Their MSN is called EAZ and usually corresponds to the direct-dial number. For the configuration under Linux, it should be sufficient to enter the last digit of the EAZ. As a last resort, try each of the digits from 1 to 9.

For the connection to be terminated just before the next charge unit is due, enable ChargeHUP. However, remember that may not work with every ISP. You can also enable channel bundling (multilink PPP) by selecting the corresponding option. Finally, you can enable the firewall for your link by selecting External Firewall Interface and Restart Firewall. To enable the normal user without administrator permissions to activate or deactivate the interface, select the Enable Device Control for Non-root User via KInternet.

Details opens a dialog in which to implement more complex connection schemes which are not relevant for normal home users. Leave the Details dialog by selecting OK.

In the next dialog, configure IP address settings. If you have not been given a static IP by your provider, select Dynamic IP Address. Otherwise, use the fields provided to enter your host's local IP address and the remote IP address according to the specifications of your ISP. If the interface should be the default route to the Internet, select Default Route. Each host can only have one interface configured as the default route. Leave this dialog by selecting Next.

The following dialog allows you to set your country and select an ISP. The ISPs included in the list are call-by-call providers only. If your ISP is not in the list, select New. This opens the Provider Parameters dialog in which to enter all the details for your ISP. When entering the phone number, do not include any blanks or commas among the digits. Finally, enter your login and the password as provided by the ISP. When finished, select Next.

To use Dial on Demand on a stand-alone workstation, specify the name server (DNS server) as well. Most ISPs support dynamic DNS, which means the IP address of a name server is sent by the ISP each time you connect. For a single workstation, however, you still need to provide a placeholder address like 192.168.22.99. If your ISP does not support dynamic DNS, specify the name server IP addresses of the ISP. If desired, specify a time-out for the connection—the period of network inactivity (in seconds) after which the connection should be automatically terminated. Confirm your settings with Next. YaST displays a summary of the configured interfaces. To activate these settings, select OK.

21.4.4. Cable Modem

[Tip]IBM System z: Cable Modem

The configuration of this type of hardware is not supported on IBM System z platforms.

In some countries it is quite common to access the Internet through the TV cable network. The TV cable subscriber usually gets a modem that is connected to the TV cable outlet on one side and to a computer network card on the other (using a 10Base-TG twisted pair cable). The cable modem then provides a dedicated Internet connection with a fixed IP address.

Depending on the instructions provided by your ISP, when configuring the network card either select Dynamic Address or Statically Assigned IP Address. Most providers today use DHCP. A static IP address often comes as part of a special business account.

21.4.5. DSL

[Tip]IBM System z: DSL

The configuration of this type of hardware is not supported on IBM System z platforms.

To configure your DSL device, select the DSL module from the YaST Network Devices section. This YaST module consists of several dialogs in which to set the parameters of DSL links based on one of the following protocols:

  • PPP over Ethernet (PPPoE)

  • PPP over ATM (PPPoATM)

  • CAPI for ADSL (Fritz Cards)

  • Point-to-Point Tunneling Protocol (PPTP)—Austria

In the DSL Devices tab of the DSL Configuration Overview dialog, you will find a list of installed DSL devices. To change the configuration of a DSL device, select it in the list and click Edit. If you click Add, you can manually configure a new DSL device.

The configuration of a DSL connection based on PPPoE or PPTP requires that the corresponding network card be set up in the correct way. If you have not done so yet, first configure the card by selecting Configure Network Cards (see Section 21.4.1, “Configuring the Network Card with YaST”). In the case of a DSL link, addresses may be assigned automatically but not via DHCP, which is why you should not enable the option Dynamic Address. Instead, enter a static dummy address for the interface, such as 192.168.22.1. In Subnet Mask, enter 255.255.255.0. If you are configuring a stand-alone workstation, leave Default Gateway empty.

[Tip]

Values in IP Address and Subnet Mask are only placeholders. They are only needed to initialize the network card and do not represent the DSL link as such.

In the first DSL configuration dialog (see Figure 21.7, “DSL Configuration”), select the PPP Mode and the Ethernet Card to which the DSL modem is connected (in most cases, this is eth0). Then use Activate Device to specify whether the DSL link should be established during the boot process. Click Enable Device Control for Non-root User via KInternet to authorize the normal user without root permissions to activate or deactivate the interface with KInternet.

In the next dialog select your country and choose from a number of ISPs operating in it. The details of any subsequent dialogs of the DSL configuration depend on the options set so far, which is why they are only briefly mentioned in the following paragraphs. For details on the available options, read the detailed help available from the dialogs.

Figure 21.7. DSL Configuration

DSL Configuration

To use Dial on Demand on a stand-alone workstation, also specify the name server (DNS server). Most ISPs support dynamic DNS—the IP address of a name server is sent by the ISP each time you connect. For a single workstation, however, provide a placeholder address like 192.168.22.99. If your ISP does not support dynamic DNS, enter the name server IP address provided by your ISP.

Idle Time-Out (seconds) defines a period of network inactivity after which to terminate the connection automatically. A reasonable time-out value is between 60 and 300 seconds. If Dial on Demand is disabled, it may be useful to set the time-out to zero to prevent automatic hang-up.

The configuration of T-DSL is very similar to the DSL setup. Just select T-Online as your provider and YaST opens the T-DSL configuration dialog. In this dialog, provide some additional information required for T-DSL—the line ID, the T-Online number, the user code and your password. All of these should be included in the information you received after subscribing to T-DSL.

21.4.6. IBM System z: Configuring Network Devices

SUSE Linux Enterprise Server for IBM System z supports several different types of network interfaces. YaST can be used to configure all of them.

21.4.6.1. The qeth-hsi Device

To add a qeth-hsi (Hipersockets) interface to the installed system, start the Network Devices+Network Settings module in YaST. Select one of the devices marked Hipersocket to use as the READ device address and click Edit. Enter the device numbers for the read, write and control channels (example device number format: 0.0.0600). Then click next. In the Network Address Setup dialog, specify the IP address and netmask for the new interface and leave the network configuration by pressing Next and OK.

21.4.6.2. The qeth-ethernet Device

To add a qeth-ethernet (IBM OSA Express Ethernet Card) interface to the installed system, start the Network Devices+Network Settings module in YaST. Select one of the devices marked IBM OSA Express Ethernet Card to use as the READ device address and click Edit. Enter a device number for the read, write and control channels (example device number format: 0.0.0600). Enter the needed port name, port number (if applicable) and some additional options (see the Linux for IBM System z: Device Drivers, Features, and Commands manual for reference, http://www.ibm.com/developerworks/linux/linux390/documentation_novell_suse.html), your IP address, and an appropriate netmask. Leave the network configuration with Next and OK.

21.4.6.3. The ctc Device

To add a ctc (IBM parallel CTC Adapter) interface to the installed system, start the Network Devices+Network Settings module in YaST. Select one of the devices marked IBM Parallel CTC Adapter to use as your read channel and click Configure. Choose the Device Settings that fit your devices (usually this would be Compatibility Mode). Specify both your IP address and the IP address of the remote partner. If needed, adjust the MTU size with Advanced+Detailed Settings. Leave the network configuration with Next and OK.

[Warning]

The use of this interface is deprecated. This interface will not be supported in future versions of SUSE Linux Enterprise Server.

21.4.6.4. The lcs Device

To add an lcs (IBM OSA-2 Adapter) interface to the installed system, start the Network Devices+Network Settings module in YaST. Select one of the devices marked IBM OSA-2 Adapter and click Configure. Enter the needed port number, some additional options (see the Linux for IBM System z: Device Drivers, Features, and Commands manual for reference, http://www.ibm.com/developerworks/linux/linux390/documentation_novell_suse.html), your IP address and an appropriate netmask. Leave the network configuration with Next and OK.

21.4.6.5. The IUCV Device

To add an iucv (IUCV) interface to the installed system, start the Network Devices+Network Settings module in YaST. Select a device marked IUCV and click Edit. YaST prompts you for the name of your IUCV partner (Peer). Enter the name (this entry is case-sensitive) and select Next. Specify both the IP Address and the Remote IP Address of your partner. If needed, Set MTU size on General tab. Leave the network configuration with Next and OK.

[Warning]

The use of this interface is deprecated. This interface will not be supported in future versions of SUSE Linux Enterprise Server.

21.5. NetworkManager

NetworkManager is the ideal solution for laptops and other portable computers. With NetworkManager, you do not need to worry about configuring network interfaces and switching between networks when you are moving.

21.5.1. NetworkManager and ifup

However, NetworkManager is not a suitable solution for all cases, so you can still choose between the traditional method for managing network connections (ifup) and NetworkManager. If you want to manage your network connection with NetworkManager, enable NetworkManager in the YaST Network Settings module as described in Section 26.2, “Enabling or Disabling NetworkManager” and configure your network connections with NetworkManager. For a list of use cases and a detailed description of how to configure and use NetworkManager, refer to Chapter 26, Using NetworkManager.

Some differences between ifup and NetworkManager include:

root Privileges

If you use NetworkManager for network setup, you can easily switch, stop or start your network connection at any time from within your desktop environment using an applet. NetworkManager also makes it possible to change and configure wireless card connections without requiring root privileges. For this reason, NetworkManager is the ideal solution for a mobile workstation.

Traditional configuration with ifup also provides some ways to switch, stop or start the connection with or without user intervention, like user-managed devices. However, this always requires root privileges to change or configure a network device. This is often a problem for mobile computing, where it is not possible to preconfigure all the connection possibilities.

Types of Network Connections

Both traditional configuration and NetworkManager can handle network connections with a wireless network (with WEP, WPA-PSK, and WPA-Enterprise access) and wired networks using DHCP and static configuration. They also support connection through dial-up, DSL and VPN. With NetworkManager you can also connect a mobile broadband (3G) modem, which is not possible with the traditional configuration.

NetworkManager tries to keep your computer connected at all times using the best connection available. If the network cable is accidentally disconnected, it tries to reconnect. It can find the network with the best signal strength from the list of your wireless connections and automatically use it to connect. To get the same functionality with ifup, a great deal of configuration effort is required.

21.5.2. NetworkManager Functionality and Configuration Files

The individual network connection settings created with NetworkManager are stored in configuration profiles. The system connections configured with either NetworkManager or YaST are saved in /etc/networkmanager/system-connections/* or in /etc/sysconfig/network/ifcfg-*. Any user-defined connections are stored in GConf for GNOME or $HOME/.kde4/share/apps/networkmanagement/* for KDE.

In case no profile is configured, NetworkManager automatically creates one and names it Auto $INTERFACE-NAME. That is made in an attempt to work without any configuration for as many cases as (securely) possible. If the automatically created profiles do not suit your needs, use the network connection configuration dialogs provided by KDE or GNOME to modify them as desired. For more information, refer to Section 26.3, “Configuring Network Connections”.

21.5.3. Controlling and Locking Down NetworkManager Features

On centrally administered machines, certain NetworkManager features can be controlled or disabled with PolicyKit, for example if a user is allowed to modify administrator defined connections or if a user is allowed to define his own network configurations. To view or change the respective NetworkManager policies, start the graphical Authorizations tool for PolicyKit. In the tree on the left side, find them below the network-manager-settings entry. For an introduction to PolicyKit and details on how to use it, refer to Chapter 9, PolicyKit (↑Security Guide).

21.6. Configuring a Network Connection Manually

Manual configuration of the network software should always be the last alternative. Using YaST is recommended. However, this background information about the network configuration can also assist your work with YaST.

When the Kernel detects a network card and creates a corresponding network interface, it assigns the device a name depending on the order of device discovery, or order of the loading of the Kernel modules. The default Kernel device names are only predictable in very simple or tightly controlled hardware environments. Systems which allow adding or removing hardware during runtime or support automatic configuration of devices cannot expect stable network device names assigned by the Kernel across reboots.

However, all system configuration tools rely on persistent interface names. This problem is solved by udev. The udev persistent net generator (/lib/udev/rules.d/75-persistent-net-generator.rules) generates a rule matching the hardware (using its hardware address by default) and assigns a persistently unique interface for the hardware. The udev database of network interfaces is stored in the file /etc/udev/rules.d/70-persistent-net.rules. Every line in the file describes one network interface and specifies its persistent name. System administrators can change the assigned names by editing the NAME="" entries. The persistent rules can also be modified using YaST.

Table 21.5, “Manual Network Configuration Scripts” summarizes the most important scripts involved in the network configuration.

Table 21.5. Manual Network Configuration Scripts

Command

Function

ifup, ifdown, ifstatus

The if scripts start or stop network interfaces, or return the status of the specified interface. For more information, see the ifup manual page.

rcnetwork

The rcnetwork script can be used to start, stop or restart all network interfaces (or just a specified one). Use rcnetwork stop to stop, rcnetwork start to start and rcnetwork restart to restart network interfaces. If you want to stop, start or restart just one interface, use the command followed by the interface name, for example rcnetwork restart eth0. The rcnetwork status command displays the state of the interfaces, their IP addresses and whether a DHCP client is running. With rcnetwork stop-all-dhcp-clients and rcnetwork restart-all-dhcp-clients you can stop or restart DHCP clients running on network interfaces.


For more information about udev and persistent device names, see Chapter 14, Dynamic Kernel Device Management with udev.

21.6.1. Configuration Files

This section provides an overview of the network configuration files and explains their purpose and the format used.

21.6.1.1. /etc/sysconfig/network/ifcfg-*

These files contain the configurations for network interfaces. They include information such as the start mode and the IP address. Possible parameters are described in the manual page of ifup. Additionally, most variables from the dhcp file can be used in the ifcfg-* files if a general setting should be used for only one interface. However, most of the /etc/sysconfig/network/config variables are global and cannot be overridden in ifcfg-files. For example NETWORKMANAGER or NETCONFIG_* variables are global.

For ifcfg.template, see Section 21.6.1.2, “/etc/sysconfig/network/config and /etc/sysconfig/network/dhcp.

►System z: IBM System z do not support USB. The names of the interface files and network aliases contain System z-specific elements like qeth.

21.6.1.2. /etc/sysconfig/network/config and /etc/sysconfig/network/dhcp

The file config contains general settings for the behavior of ifup, ifdown and ifstatus. dhcp contains settings for DHCP. The variables in both configuration files are commented. Some of the variables from /etc/sysconfig/network/config can also be used in ifcfg-* files, where they are given a higher priority. The /etc/sysconfig/network/ifcfg.template file lists variables that can be specified in a per interface scope. However, most of the /etc/sysconfig/network/config variables are global and cannot be overridden in ifcfg-files. For example, NETWORKMANAGER or NETCONFIG_* variables are global.

21.6.1.3. /etc/sysconfig/network/routes and /etc/sysconfig/network/ifroute-*

The static routing of TCP/IP packets is determined here. All the static routes required by the various system tasks can be entered in the /etc/sysconfig/network/routes file: routes to a host, routes to a host via a gateway and routes to a network. For each interface that needs individual routing, define an additional configuration file: /etc/sysconfig/network/ifroute-*. Replace * with the name of the interface. The entries in the routing configuration files look like this:

# Destination     Dummy/Gateway     Netmask            Device
#
127.0.0.0         0.0.0.0           255.255.255.0      lo
204.127.235.0     0.0.0.0           255.255.255.0      eth0
default           204.127.235.41    0.0.0.0            eth0
207.68.156.51     207.68.145.45     255.255.255.255    eth1
192.168.0.0       207.68.156.51     255.255.0.0        eth1

The route's destination is in the first column. This column may contain the IP address of a network or host or, in the case of reachable name servers, the fully qualified network or hostname.

The second column contains the default gateway or a gateway through which a host or network can be accessed. The third column contains the netmask for networks or hosts behind a gateway. For example, the mask is 255.255.255.255 for a host behind a gateway.

The fourth column is only relevant for networks connected to the local host such as loopback, Ethernet, ISDN, PPP and dummy device. The device name must be entered here.

An (optional) fifth column can be used to specify the type of a route. Columns that are not needed should contain a minus sign - to ensure that the parser correctly interprets the command. For details, refer to the routes(5) man page.

The unified format for IPv4 and IPv6 now looks as follows:

prefix/lengthgateway -            [interface]

And the so-called compatibility format looks accordingly:

prefixgatewaylength       [interface]

For IPv4 you still can use the old format with netmask:

ipv4-networkgatewayipv4-netmask [interface]

The following examples are equivalent:

2001:db8:abba:cafe::/64 2001:db8:abba:cafe::dead  -            eth0
208.77.188.0/24         208.77.188.166            -            eth0

2001:db8:abba:cafe::    2001:db8:abba:cafe::dead 64            eth0
208.77.188.0            208.77.188.166           24            eth0

208.77.188.0            208.77.188.166           255.255.255.0 eth0

21.6.1.4. /etc/resolv.conf

The domain to which the host belongs is specified in this file (keyword search). Also listed is the status of the name server address to access (keyword nameserver). Multiple domain names can be specified in the file. When resolving a name that is not fully qualified, an attempt is made to generate one by attaching the individual search entries. Multiple name servers can be specified in multiple lines, each beginning with nameserver. Comments are preceded by # signs. Example 21.5, “/etc/resolv.conf shows what /etc/resolv.conf could look like.

However, the /etc/resolv.conf should not be edited by hand. Instead, it is generated by the netconfig script. To define static DNS configuration without using YaST, edit the appropriate variables manually in the /etc/sysconfig/network/config file:

NETCONFIG_DNS_STATIC_SEARCHLIST

list of DNS domain names used for hostname lookup

NETCONFIG_DNS_STATIC_SERVERS

list of name server IP addresses to use for hostname lookup

NETCONFIG_DNS_FORWARDER

defines the name of the DNS forwarder that has to be configured

To disable DNS configuration using netconfig, set NETCONFIG_DNS_POLICY=''. For more information about netconfig, see man 8 netconfig.

Example 21.5. /etc/resolv.conf

# Our domain
search example.com
#
# We use dns.example.com (192.168.1.116) as name server
nameserver 192.168.1.116

21.6.1.5. /sbin/netconfig

netconfig is a modular tool to manage additional network configuration settings. It merges statically defined settings with settings provided by autoconfiguration mechanisms as DHCP or PPP according to a predefined policy. The required changes are applied to the system by calling the netconfig modules that are responsible for modifying a configuration file and restarting a service or a similar action.

netconfig recognizes three main actions. The netconfig modify and netconfig remove commands are used by daemons such as DHCP or PPP to provide or remove settings to netconfig. Only the netconfig update command is available for the user:

modify

The netconfig modify command modifies the current interface and service specific dynamic settings and updates the network configuration. Netconfig reads settings from standard input or from a file specified with the --lease-file filename option and internally stores them until a system reboot (or the next modify or remove action). Already existing settings for the same interface and service combination are overwritten. The interface is specified by the -i interface_name parameter. The service is specified by the -s service_name parameter.

remove

The netconfig remove command removes the dynamic settings provided by a modificatory action for the specified interface and service combination and updates the network configuration. The interface is specified by the -i interface_name parameter. The service is specified by the -s service_name parameter.

update

The netconfig update command updates the network configuration using current settings. This is useful when the policy or the static configuration has changed. Use the -m module_type parameter, if you want to update a specified service only (dns, nis, or ntp).

The netconfig policy and the static configuration settings are defined either manually or using YaST in the /etc/sysconfig/network/config file. The dynamic configuration settings provided by autoconfiguration tools as DHCP or PPP are delivered directly by these tools with the netconfig modify and netconfig remove actions. NetworkManager also uses netconfig modify and netconfig remove actions. When NetworkManager is enabled, netconfig (in policy mode auto) uses only NetworkManager settings, ignoring settings from any other interfaces configured using the traditional ifup method. If NetworkManager does not provide any setting, static settings are used as a fallback. A mixed usage of NetworkManager and the traditional ifup method is not supported.

For more information about netconfig, see man 8 netconfig.

21.6.1.6. /etc/hosts

In this file, shown in Example 21.6, “/etc/hosts, IP addresses are assigned to hostnames. If no name server is implemented, all hosts to which an IP connection will be set up must be listed here. For each host, enter a line consisting of the IP address, the fully qualified hostname, and the hostname into the file. The IP address must be at the beginning of the line and the entries separated by blanks and tabs. Comments are always preceded by the # sign.

Example 21.6. /etc/hosts

127.0.0.1 localhost
192.168.2.100 jupiter.example.com jupiter
192.168.2.101 venus.example.com venus

21.6.1.7. /etc/networks

Here, network names are converted to network addresses. The format is similar to that of the hosts file, except the network names precede the addresses. See Example 21.7, “/etc/networks.

Example 21.7. /etc/networks

loopback     127.0.0.0
localnet     192.168.0.0

21.6.1.8. /etc/host.conf

Name resolution—the translation of host and network names via the resolver library—is controlled by this file. This file is only used for programs linked to libc4 or libc5. For current glibc programs, refer to the settings in /etc/nsswitch.conf. A parameter must always stand alone in its own line. Comments are preceded by a # sign. Table 21.6, “Parameters for /etc/host.conf” shows the parameters available. A sample /etc/host.conf is shown in Example 21.8, “/etc/host.conf.

Table 21.6. Parameters for /etc/host.conf

order hosts, bind

Specifies in which order the services are accessed for the name resolution. Available arguments are (separated by blank spaces or commas):

hosts: searches the /etc/hosts file

bind: accesses a name server

nis: uses NIS

multi on/off

Defines if a host entered in /etc/hosts can have multiple IP addresses.

nospoof on spoofalert on/off

These parameters influence the name server spoofing but do not exert any influence on the network configuration.

trim domainname

The specified domain name is separated from the hostname after hostname resolution (as long as the hostname includes the domain name). This option is useful only if names from the local domain are in the /etc/hosts file, but should still be recognized with the attached domain names.


Example 21.8. /etc/host.conf

# We have named running
order hosts bind
# Allow multiple address
multi on

21.6.1.9. /etc/nsswitch.conf

The introduction of the GNU C Library 2.0 was accompanied by the introduction of the Name Service Switch (NSS). Refer to the nsswitch.conf(5) man page and The GNU C Library Reference Manual for details.

The order for queries is defined in the file /etc/nsswitch.conf. A sample nsswitch.conf is shown in Example 21.9, “/etc/nsswitch.conf. Comments are preceded by # signs. In this example, the entry under the hosts database means that a request is sent to /etc/hosts (files) via DNS (see Chapter 24, The Domain Name System).

Example 21.9. /etc/nsswitch.conf

passwd:     compat
group:      compat

hosts:      files dns
networks:   files dns

services:   db files
protocols:  db files
rpc:        files
ethers:     files
netmasks:   files
netgroup:   files nis
publickey:  files

bootparams: files
automount:  files nis
aliases:    files nis
shadow:     compat

The databases available over NSS are listed in Table 21.7, “Databases Available via /etc/nsswitch.conf”. The configuration options for NSS databases are listed in Table 21.8, “Configuration Options for NSS Databases.

Table 21.7. Databases Available via /etc/nsswitch.conf

aliases

Mail aliases implemented by sendmail; see man 5 aliases.

ethers

Ethernet addresses.

netmasks

List of network and their subnet masks. Only needed, if you use subnetting.

group

For user groups used by getgrent. See also the man page for group.

hosts

For hostnames and IP addresses, used by gethostbyname and similar functions.

netgroup

Valid host and user lists in the network for the purpose of controlling access permissions; see the netgroup(5) man page.

networks

Network names and addresses, used by getnetent.

publickey

Public and secret keys for Secure_RPC used by NFS and NIS+.

passwd

User passwords, used by getpwent; see the passwd(5) man page.

protocols

Network protocols, used by getprotoent; see the protocols(5) man page.

rpc

Remote procedure call names and addresses, used by getrpcbyname and similar functions.

services

Network services, used by getservent.

shadow

Shadow passwords of users, used by getspnam; see the shadow(5) man page.


Table 21.8. Configuration Options for NSS Databases

files

directly access files, for example, /etc/aliases

db

access via a database

nis, nisplus

NIS, see also Chapter 3, Using NIS (↑Security Guide)

dns

can only be used as an extension for hosts and networks

compat

can only be used as an extension for passwd, shadow and group


21.6.1.10. /etc/nscd.conf

This file is used to configure nscd (name service cache daemon). See the nscd(8) and nscd.conf(5) man pages. By default, the system entries of passwd and groups are cached by nscd. This is important for the performance of directory services, like NIS and LDAP, because otherwise the network connection needs to be used for every access to names or groups. hosts is not cached by default, because the mechanism in nscd to cache hosts makes the local system unable to trust forward and reverse lookup checks. Instead of asking nscd to cache names, set up a caching DNS server.

If the caching for passwd is activated, it usually takes about fifteen seconds until a newly added local user is recognized. Reduce this waiting time by restarting nscd with the command rcnscd restart.

21.6.1.11. /etc/HOSTNAME

This contains the fully qualified hostname with the domain name attached. This file is read by several scripts while the machine is booting. It must contain only one line (in which the hostname is set).

21.6.2. Testing the Configuration

Before you write your configuration to the configuration files, you can test it. To set up a test configuration, use the ip command. To test the connection, use the ping command. Older configuration tools, ifconfig and route, are also available.

The commands ip, ifconfig and route change the network configuration directly without saving it in the configuration file. Unless you enter your configuration in the correct configuration files, the changed network configuration is lost on reboot.

21.6.2.1. Configuring a Network Interface with ip

ip is a tool to show and configure network devices, routing, policy routing, and tunnels.

ip is a very complex tool. Its common syntax is ip options object command. You can work with the following objects:

link

This object represents a network device.

address

This object represents the IP address of device.

neighbor

This object represents a ARP or NDISC cache entry.

route

This object represents the routing table entry.

rule

This object represents a rule in the routing policy database.

maddress

This object represents a multicast address.

mroute

This object represents a multicast routing cache entry.

tunnel

This object represents a tunnel over IP.

If no command is given, the default command is used (usually list).

Change the state of a device with the command ip link set device_name command. For example, to deactivate device eth0, enter ip link set eth0 down. To activate it again, use ip link set eth0 up.

After activating a device, you can configure it. To set the IP address, use ip addr add ip_address + dev device_name. For example, to set the address of the interface eth0 to 192.168.12.154/30 with standard broadcast (option brd), enter ip addr add 192.168.12.154/30 brd + dev eth0.

To have a working connection, you must also configure the default gateway. To set a gateway for your system, enter ip route add gateway_ip_address. To translate one IP address to another, use nat: ip route add nat ip_address via other_ip_address.

To display all devices, use ip link ls. To display the running interfaces only, use ip link ls up. To print interface statistics for a device, enter ip -s link ls device_name. To view addresses of your devices, enter ip addr. In the output of the ip addr, also find information about MAC addresses of your devices. To show all routes, use ip route show.

For more information about using ip, enter ip help or see the ip(8) man page. The help option is also available for all ip subcommands. If, for example, you need help for ip addr, enter ip addr help. Find the ip manual in /usr/share/doc/packages/iproute2/ip-cref.pdf.

21.6.2.2. Testing a Connection with ping

The ping command is the standard tool for testing whether a TCP/IP connection works. It uses the ICMP protocol to send a small data packet, ECHO_REQUEST datagram, to the destination host, requesting an immediate reply. If this works, ping displays a message to that effect, which indicates that the network link is basically functioning.

ping does more than only test the function of the connection between two computers: it also provides some basic information about the quality of the connection. In Example 21.10, “Output of the Command ping”, you can see an example of the ping output. The second-to-last line contains information about the number of transmitted packets, packet loss, and total time of ping running.

As the destination, you can use a hostname or IP address, for example, ping example.com or ping 192.168.3.100. The program sends packets until you press Ctrl+C.

If you only need to check the functionality of the connection, you can limit the number of the packets with the -c option. For example to limit ping to three packets, enter ping -c 3 example.com.

Example 21.10. Output of the Command ping

ping -c 3 example.com
PING example.com (192.168.3.100) 56(84) bytes of data.
64 bytes from example.com (192.168.3.100): icmp_seq=1 ttl=49 time=188 ms
64 bytes from example.com (192.168.3.100): icmp_seq=2 ttl=49 time=184 ms
64 bytes from example.com (192.168.3.100): icmp_seq=3 ttl=49 time=183 ms
--- example.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2007ms
rtt min/avg/max/mdev = 183.417/185.447/188.259/2.052 ms

The default interval between two packets is one second. To change the interval, ping provides the option -i. For example, to increase the ping interval to ten seconds, enter ping -i 10 example.com.

In a system with multiple network devices, it is sometimes useful to send the ping through a specific interface address. To do so, use the -I option with the name of the selected device, for example, ping -I wlan1 example.com.

For more options and information about using ping, enter ping -h or see the ping (8) man page.

[Tip]Pinging IPv6 Addresses

For IPv6 addresses use the ping6 command. Note, to ping link-local addresses, you must specify the interface with -I. The following command works, if the address is reachable via eth1:

ping6 -I eth1 fe80::117:21ff:feda:a425

21.6.2.3. Configuring the Network with ifconfig

ifconfig is a network configuration tool.

[Note]ifconfig and ip

The ifconfig tool is obsolete. Use ip instead. In contrast to ip, you can use ifconfig only for interface configuration. It limits interface names to 9 characters.

Without arguments, ifconfig displays the status of the currently active interfaces. As you can see in Example 21.11, “Output of the ifconfig Command”, ifconfig has very well-arranged and detailed output. The output also contains information about the MAC address of your device (the value of HWaddr) in the first line.

Example 21.11. Output of the ifconfig Command

eth0      Link encap:Ethernet  HWaddr 00:08:74:98:ED:51
          inet6 addr: fe80::208:74ff:fe98:ed51/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:634735 errors:0 dropped:0 overruns:4 frame:0
          TX packets:154779 errors:0 dropped:0 overruns:0 carrier:1
          collisions:0 txqueuelen:1000
          RX bytes:162531992 (155.0 Mb)  TX bytes:49575995 (47.2 Mb)
          Interrupt:11 Base address:0xec80

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:8559 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8559 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:533234 (520.7 Kb)  TX bytes:533234 (520.7 Kb)    

wlan1     Link encap:Ethernet  HWaddr 00:0E:2E:52:3B:1D
          inet addr:192.168.2.4  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::20e:2eff:fe52:3b1d/64 Scope:Link
          UP BROADCAST NOTRAILERS RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:50828 errors:0 dropped:0 overruns:0 frame:0
          TX packets:43770 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:45978185 (43.8 Mb)  TX bytes:7526693 (7.1 MB)

For more options and information about using ifconfig, enter ifconfig -h or see the ifconfig (8) man page.

21.6.2.4. Configuring Routing with route

route is a program for manipulating the IP routing table. You can use it to view your routing configuration and to add or remove routes.

[Note]route and ip

The program route is obsolete. Use ip instead.

route is especially useful if you need quick and comprehensible information about your routing configuration to determine problems with routing. To view your current routing configuration, enter route -n as root.

Example 21.12. Output of the route -n Command

route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.20.0.0       *               255.255.248.0   U         0 0          0 eth0
link-local      *               255.255.0.0     U         0 0          0 eth0
loopback        *               255.0.0.0       U         0 0          0 lo
default         styx.exam.com   0.0.0.0         UG        0 0          0 eth0

For more options and information about using route, enter route -h or see the route (8) man page.

21.6.3. Start-Up Scripts

Apart from the configuration files described above, there are also various scripts that load the network programs while the machine is booting. These are started as soon as the system is switched to one of the multiuser runlevels. Some of these scripts are described in Table 21.9, “Some Start-Up Scripts for Network Programs”.

Table 21.9. Some Start-Up Scripts for Network Programs

/etc/init.d/network

This script handles the configuration of the network interfaces. If the network service was not started, no network interfaces are implemented.

/etc/init.d/xinetd

Starts xinetd. xinetd can be used to make server services available on the system. For example, it can start vsftpd whenever an FTP connection is initiated.

/etc/init.d/rpcbind

Starts the rpcbind utility that converts RPC program numbers to universal addresses. It is needed for RPC services, such as an NFS server.

/etc/init.d/nfsserver

Starts the NFS server.

/etc/init.d/postfix

Controls the postfix process.

/etc/init.d/ypserv

Starts the NIS server.

/etc/init.d/ypbind

Starts the NIS client.


21.7. Setting Up Bonding Devices

For some systems, there is a desire to implement network connections that comply to more than the standard data security or availability requirements of a typical Ethernet device. In these cases, several Ethernet devices can be aggregated to a single bonding device.

The configuration of the bonding device is done by means of bonding module options. The behavior is mainly affected by the mode of the bonding device. By default, this is mode=active-backup which means that a different slave device will become active if the active slave fails.

[Tip]Bonding and Xen

Using bonding devices is only of interest for machines where you have multiple real network cards available. In most configurations, this means that you should use the bonding configuration only in Domain0. Only if you have multiple network cards assigned to a VM Guest system it may also be useful to set up the bond in a VM Guest.

To configure a bonding device, use the following procedure:

  1. Run YaST+Network Devices+Network Settings.

  2. Use Add and change the Device Type to Bond. Proceed with Next.

  3. Select how to assign the IP address to the bonding device. Three methods are at your disposal:

    • No IP Address

    • Dynamic Address (with DHCP or Zeroconf)

    • Statically assigned IP Address

    Use the method that is appropriate for your environment.

  4. In the Bond Slaves tab, select the Ethernet devices that should be included into the bond by activating the related check box.

  5. Edit the Bond Driver Options. The modes that are available for configuration are the following:

    • balance-rr

    • active-backup

    • balance-xor

    • broadcast

    • 802.3ad

    • balance-tlb

    • balance-alb

  6. Make sure that the parameter miimon=100 is added to the Bond Driver Options. Without this parameter, the data integrity is not checked regularly.

  7. Click Next and leave YaST with OK to create the device.

All modes, and many more options are explained in detail in the Linux Ethernet Bonding Driver HOWTO found at /usr/src/linux/Documentation/networking/bonding.txt after installing the package kernel-source.

21.7.1. Hotplugging of Bonding Slaves

In specific network environments (such as High Availability), there are cases when you need to replace a bonding slave interface with another one. The reason may be a constantly failing network device. The solution is to set up hotplugging of bonding slaves.

The bond is configured as usual (according to man 5 ifcfg-bonding), for example:

ifcfg-bond0   
          STARTMODE='auto' # or 'onboot'  
          BOOTPROTO='static'   
          IPADDR='192.168.0.1/24'   
          BONDING_MASTER='yes'   
          BONDING_SLAVE_0='eth0'   
          BONDING_SLAVE_1='eth1'   
          BONDING_MODULE_OPTS='mode=active-backup miimon=100'

but the slaves are specified with STARTMODE=hotplug and BOOTPROTO=none:

ifcfg-eth0   
          STARTMODE='hotplug'   
          BOOTPROTO='none'   

ifcfg-eth1   
          STARTMODE='hotplug'   
          BOOTPROTO='none'

BOOTPROTO=none uses the ethtool options (when provided), but does not set the link up on ifup eth0. The reason is that the slave interface is controlled by the bond master.

STARTMODE=hotplug causes the slave interface to join the bond automatically as soon as it is available.

The udev rules in /etc/udev/rules.d/70-persistent-net.rules have to be changed to match the device by bus ID (udev KERNELS keyword equal to "SysFS BusID" as visible in hwinfo --netcard) instead of by MAC address to allow to replacement of defective hardware (a network card in the same slot but with a different MAC), and to avoid confusion as the bond changes the MAC address of all its slaves.

For example:

SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*",
KERNELS=="0000:00:19.0", ATTR{dev_id}=="0x0", ATTR{type}=="1",
KERNEL=="eth*", NAME="eth0"

At boot time, /etc/init.d/network does not wait for the hotplug slaves, but for the bond to become ready, which requires at least one available slave. When one of the slave interfaces gets removed (unbind from NIC driver, rmmod of the NIC driver or true PCI hotplug remove) from the system, the kernel removes it from the bond automatically. When a new card is added to the system (replacement of the hardware in the slot), udev renames it using the bus-based persistent name rule to the name of the slave, and calls ifup for it. The ifup call automatically joins it into the bond.

21.8. smpppd as Dial-up Assistant

Some home users do not have a dedicated line connecting them to the Internet. Instead, they use dial-up connections. Depending on the dial-up method (ISDN or DSL), the connection is controlled by ipppd or pppd. Basically, all that needs to be done to go online is to start these programs correctly.

If you have a flat-rate connection that does not generate any additional costs for the dial-up connection, simply start the respective daemon. Control the dial-up connection with a desktop applet or a command-line interface. If the Internet gateway is not the host you are using, you might want to control the dial-up connection by way of a network host.

This is where smpppd (SUSE Meta PPP Daemon) is involved. It provides a uniform interface for auxiliary programs and acts in two directions. First, it programs the required pppd or ipppd and controls its dial-up properties. Second, it makes various providers available to the user programs and transmits information about the current status of the connection. As smpppd can also be controlled by way of the network, it is suitable for controlling dial-up connections to the Internet from a workstation in a private subnetwork.

21.8.1. Configuring smpppd

The connections provided by smpppd are automatically configured by YaST. The actual dial-up programs KInternet and cinternet are also pre-configured. Manual settings are only required to configure additional features of smpppd such as remote control.

The configuration file of smpppd is /etc/smpppd.conf. By default, it does not enable remote control. The most important options of this configuration file are:

open-inet-socket = yes|no

To control smpppd via the network, set this option to yes. smpppd listens on port 3185. If this parameter is set to yes, the parameters bind-address, host-range and password must be set accordingly.

bind-address = ip address

If a host has several IP addresses, use this parameter to determine at which IP address smpppd should accept connections. The default is to listen at all addresses.

host-range = min ipmax ip

The parameter host-range defines a network range. Hosts whose IP addresses are within this range are granted access to smpppd. All hosts not within this range are denied access.

password = password

By assigning a password, limit the clients to authorized hosts. As this is a plain-text password, you should not overrate the security it provides. If no password is assigned, all clients are permitted to access smpppd.

slp-register = yes|no

With this parameter, the smpppd service can be announced in the network via SLP.

More information about smpppd is available in the smpppd(8) and smpppd.conf(5) man pages.

21.8.2. Configuring cinternet for Remote Use

cinternet can be used to control a local or remote smpppd. cinternet is the command-line counterpart to the graphical KInternet. To prepare these utilities for use with a remote smpppd, edit the configuration file /etc/smpppd-c.conf manually or using cinternet. This file only uses four options:

sites = list of sites

list of sites where the front-ends search for smpppd. The front-ends test the options in the order specified here. local orders the establishment of a connection to the local smpppd. gateway points to an smpppd on the gateway. config-file indicates that the connection should be established to the smpppd specified in the server and port options in /etc/smpppd-c.conf. slp orders the front-ends to connect to an smpppd found via SLP.

server = server

The host on which smpppd runs.

port = port

The port on which smpppd runs.

password = password

The password selected for smpppd.

If smpppd is active, try to access it. For example, with cinternet --verbose --interface-list. In case of difficulties at this point, refer to the smpppd-c.conf(5) and cinternet(8) man pages.

Chapter 22. SLP Services in the Network

Abstract

The service location protocol (SLP) was developed to simplify the configuration of networked clients within a local network. To configure a network client, including all required services, the administrator traditionally needs detailed knowledge of the servers available in the network. SLP makes the availability of selected services known to all clients in the local network. Applications that support SLP can use the information distributed and be configured automatically.

SUSE® Linux Enterprise Server supports installation using installation sources provided with SLP and contains many system services with integrated support for SLP. YaST and Konqueror both have appropriate front-ends for SLP. You can use SLP to provide networked clients with central functions, such as an installation server, file server, or print server on your system.

[Important]SLP Support in SUSE Linux Enterprise Server

Services that offer SLP support include cupsd, rsyncd, ypserv, openldap2, ksysguardd, saned, kdm, vnc, login, smpppd, rpasswd , postfix, and sshd (via fish).

22.1. Installation

All packages necessary are installed by default. However, if you want to provide services via SLP, check that the package openslp-server is installed.

22.2. Activating SLP

slpd must run on your system to offer services with SLP. If the machine should only operate as client, and does not offer services, it is not necessary to run slpd. Like most system services in SUSE Linux Enterprise Server, the slpd daemon is controlled by means of a separate init script. After the installation, the daemon is inactive by default. To activate it temporarily, run rcslpd start as root or rcslpd stop to stop it. Perform a restart or status check with restart or status. If slpd should be always active after booting, enable slpd in YaST System+System Services (Runlevel) or run the insserv slpd command as root.

22.3. SLP Front-Ends in SUSE Linux Enterprise Server

To find services provided via SLP in your network, use an SLP front-end such as slptool (openslp package) or YaST:

slptool

slptool is a command line program that can be used to announce SLP inquiries in the network or announce proprietary services. slptool --help lists all available options and functions. For example, to find all time servers that announce themselves in the current network, run the command:

slptool findsrvs service:ntp
YaST

YaST also provides an SLP browser. However, this browser is not available from the YaST Control Center. To start it, run yast2 slp as root user. Click on a Service Type on the lefthand side to get more information about a service.

22.4. Installation over SLP

If you have an installation server with SUSE Linux Enterprise Server installation media within your network, this can be registered and offered with SLP. For details, see Section “Setting Up the Server Holding the Installation Sources” (Chapter 14, Remote Installation, ↑Deployment Guide). If SLP installation is selected, linuxrc starts an SLP inquiry after the system has booted from the selected boot medium and displays the sources found.

22.5. Providing Services via SLP

Many applications in SUSE Linux Enterprise Server have integrated SLP support through the use of the libslp library. If a service has not been compiled with SLP support, use one of the following methods to make it available via SLP:

Static Registration with /etc/slp.reg.d

Create a separate registration file for each new service. This is an example for registering a scanner service:

## Register a saned service on this system
## en means english language
## 65535 disables the timeout, so the service registration does
## not need refreshes
service:scanner.sane://$HOSTNAME:6566,en,65535
watch-port-tcp=6566
description=SANE scanner daemon

The most important line in this file is the service URL, which begins with service:. This contains the service type (scanner.sane) and the address under which the service is available on the server. $HOSTNAME is automatically replaced with the full hostname. The name of the TCP port on which the relevant service can be found follows, separated by a colon. Then enter the language in which the service should appear and the duration of registration in seconds. These should be separated from the service URL by commas. Set the value for the duration of registration between 0 and 65535. 0 prevents registration. 65535 removes all restrictions.

The registration file also contains the two variables watch-port-tcp and description. watch-port-tcp links the SLP service announcement to whether the relevant service is active by having slpd check the status of the service. The second variable contains a more precise description of the service that is displayed in suitable browsers.

[Tip]YaST and SLP

Some services brokered by YaST, such as an installation server or YOU server, perform this registration automatically when you activate SLP in the module dialogs. YaST then creates registration files for these services.

Static Registration with /etc/slp.reg

The only difference between this method and the procedure with /etc/slp.reg.d is that all services are grouped within a central file.

Dynamic Registration with slptool

If a service needs to be registered dynamically without the need of configuration files, use the slptool command line utility. The same utility can also be used to deregister an existing service offering without restarting slpd.

22.6. For More Information

RFC 2608, 2609, 2610

RFC 2608 generally deals with the definition of SLP. RFC 2609 deals with the syntax of the service URLs used in greater detail and RFC 2610 deals with DHCP via SLP.

http://www.openslp.org

The home page of the OpenSLP project.

/usr/share/doc/packages/openslp

This directory contains the documentation for SLP coming with the openslp-server package, including a README.SuSE containing the SUSE Linux Enterprise Server details, the RFCs, and two introductory HTML documents. Programmers who want to use the SLP functions find more information in the Programmers Guide that is included in the openslp-devel package.

Chapter 23. Time Synchronization with NTP

Abstract

The NTP (network time protocol) mechanism is a protocol for synchronizing the system time over the network. First, a machine can obtain the time from a server that is a reliable time source. Second, a machine can itself act as a time source for other computers in the network. The goal is twofold—maintaining the absolute time and synchronizing the system time of all machines within a network.

Maintaining an exact system time is important in many situations. The built-in hardware clock does often not meet the requirements of applications such as databases or clusters. Manual correction of the system time would lead to severe problems because, for example, a backward leap can cause malfunction of critical applications. Within a network, it is usually necessary to synchronize the system time of all machines, but manual time adjustment is a bad approach. NTP provides a mechanism to solve these problems. The NTP service continuously adjusts the system time with the help of reliable time servers in the network. It further enables the management of local reference clocks, such as radio-controlled clocks.

23.1. Configuring an NTP Client with YaST

The NTP daemon (ntpd) coming with the ntp package is preset to use the local computer clock as a time reference. Using the hardware clock, however, only serves as a fallback for cases where no time source of better precision is available. YaST facilitates the configuration of an NTP client.

23.1.1. Basic Configuration

The YaST NTP client configuration (Network Services+NTP Configuration) consists of tabs. Set the start mode of ntpd and the server to query on the General Settings tab.

Only Manually

Select Only Manually, if you want to manually start the ntpd daemon.

Now and On Boot

Select Now and On Boot to start ntpd automatically when the system is booted. This setting is strongly recommended. Then configure the server as described Section 23.1.2, “Changing Basic Configuration”.

23.1.2. Changing Basic Configuration

The servers and other time sources for the client to query are listed in the lower part of the General Settings tab. Modify this list as needed with Add, Edit, and Delete. Display Log provides the possibility to view the log files of your client.

Click Add to add a new source of time information. In the following dialog, select the type of source with which the time synchronization should be made. The following options are available:

Figure 23.1. YaST: NTP Server

YaST: NTP Server

Server

In the pull-down Select list (see Figure 23.1, “YaST: NTP Server”), determine whether to set up time synchronization using a time server from your local network (Local NTP Server) or an Internet-based time server that takes care of your time zone (Public NTP Server). For a local time server, click Lookup to start an SLP query for available time servers in your network. Select the most suitable time server from the list of search results and exit the dialog with OK. For a public time server, select your country (time zone) and a suitable server from the list under Public NTP Server then exit the dialog with OK. In the main dialog, test the availability of the selected server with Test. Options allows you to specify additional options for ntpd.

Using Access Control Options, you can restrict the actions that the remote computer can perform with the daemon running on your computer. This field is enabled only after checking Restrict NTP Service to Configured Servers Only on the Security Settings tab (see Figure 23.2, “Advanced NTP Configuration: Security Settings”). The options correspond to the restrict clauses in /etc/ntp.conf. For example, nomodify notrap noquery disallows the server to modify NTP settings of your computer and to use the trap facility (a remote event logging feature) of your NTP daemon. Using these restrictions is recommended for servers out of your control (for example, on the Internet).

Refer to /usr/share/doc/packages/ntp-doc (part of the ntp-doc package) for detailed information.

Peer

A peer is a machine to which a symmetric relationship is established: it acts both as a time server and as a client. To use a peer in the same network instead of a server, enter the address of the system. The rest of the dialog is identical to the Server dialog.

Radio Clock

To use a radio clock in your system for the time synchronization, enter the clock type, unit number, device name, and other options in this dialog. Click Driver Calibration to fine-tune the driver. Detailed information about the operation of a local radio clock is available in /usr/share/doc/packages/ntp-doc/refclock.html.

Outgoing Broadcast

Time information and queries can also be transmitted by broadcast in the network. In this dialog, enter the address to which such broadcasts should be sent. Do not activate broadcasting unless you have a reliable time source like a radio controlled clock.

Incoming Broadcast

If you want your client to receive its information via broadcast, enter the address from which the respective packets should be accepted in this fields.

Figure 23.2. Advanced NTP Configuration: Security Settings

Advanced NTP Configuration: Security Settings

In the Security Settings tab (see Figure 23.2, “Advanced NTP Configuration: Security Settings”), determine whether ntpd should be started in a chroot jail. By default, Run NTP Daemon in Chroot Jail is activated. This increases the security in the event of an attack over ntpd, as it prevents the attacker from compromising the entire system.

Restrict NTP Service to Configured Servers Only increases the security of your system by disallowing remote computers to view and modify NTP settings of your computer and to use the trap facility for remote event logging. Once enabled, these restrictions apply to all remote computers, unless you override the access control options for individual computers in the list of time sources in the General Settings tab. For all other remote computers, only querying for local time is allowed.

Enable Open Port in Firewall if SuSEfirewall2 is active (which it is by default). If you leave the port closed, it is not possible to establish a connection to the time server.

23.2. Manually Configuring NTP in the Network

The easiest way to use a time server in the network is to set server parameters. For example, if a time server called ntp.example.com is reachable from the network, add its name to the file /etc/ntp.conf by adding the following line:

server ntp.example.com

To add more time servers, insert additional lines with the keyword server. After initializing ntpd with the command rcntp start, it takes about one hour until the time is stabilized and the drift file for correcting the local computer clock is created. With the drift file, the systematic error of the hardware clock can be computed as soon as the computer is powered on. The correction is used immediately, resulting in a higher stability of the system time.

There are two possible ways to use the NTP mechanism as a client: First, the client can query the time from a known server in regular intervals. With many clients, this approach can cause a high load on the server. Second, the client can wait for NTP broadcasts sent out by broadcast time servers in the network. This approach has the disadvantage that the quality of the server is unknown and a server sending out wrong information can cause severe problems.

If the time is obtained via broadcast, you do not need the server name. In this case, enter the line broadcastclient in the configuration file /etc/ntp.conf. To use one or more known time servers exclusively, enter their names in the line starting with servers.

23.3. Dynamic Time Synchronization at Runtime

If the system boots without network connection, ntpd starts up, but it cannot resolve DNS names of the time servers set in the configuration file. This can happen if you use Network Manager with an encrypted WLAN.

If you want ntpd to resolve DNS names at runtime, you must set the dynamic option. Then, when the network is establish some time after booting, ntpd looks up the names again and can reach the time servers to get the time.

Manually edit /etc/ntp.conf and add dynamic to one or more server entries:

server ntp.example.com dynamic

Or use YaST and proceed as follows:

  1. In YaST click Network Services+NTP Configuration.

  2. Select the server you want to configure. Then click Edit.

  3. Activate the Options field and add dynamic. Separate it with a space, if there are already other options entered.

  4. Click Ok to close the edit dialog. Repeat the previous step to change all servers as wanted.

  5. Finally click Ok to save the settings.

23.4. Setting Up a Local Reference Clock

The software package ntpd contains drivers for connecting local reference clocks. A list of supported clocks is available in the ntp-doc package in the file /usr/share/doc/packages/ntp-doc/refclock.html. Every driver is associated with a number. In NTP, the actual configuration takes place by means of pseudo IP addresses. The clocks are entered in the file /etc/ntp.conf as though they existed in the network. For this purpose, they are assigned special IP addresses in the form 127.127.t.u. Here, t stands for the type of the clock and determines which driver is used and u for the unit, which determines the interface used.

Normally, the individual drivers have special parameters that describe configuration details. The file /usr/share/doc/packages/ntp-doc/drivers/driverNN.html (where NN is the number of the driver) provides information about the particular type of clock. For example, the type 8 clock (radio clock over serial interface) requires an additional mode that specifies the clock more precisely. The Conrad DCF77 receiver module, for example, has mode 5. To use this clock as a preferred reference, specify the keyword prefer. The complete server line for a Conrad DCF77 receiver module would be:

server 127.127.8.0 mode 5 prefer

Other clocks follow the same pattern. Following the installation of the ntp-doc package, the documentation for NTP is available in the directory /usr/share/doc/packages/ntp-doc. The file /usr/share/doc/packages/ntp-doc/refclock.html provides links to the driver pages describing the driver parameters.

23.5. Clock Synchronization to an External Time Reference (ETR)

Support for clock synchronization to an external time reference (ETR) is available. The external time reference sends an oscillator signal and a synchronization signal every 2**20 (2 to the power of 20) microseconds to keep TOD clocks of all connected servers in sync.

For availability two ETR units can be connected to a machine. If the clock deviates for more than the sync-check tolerance all CPUs get a machine check that indicates that the clock is out of sync. If this happens, all DASD I/O to XRC enabled devices is stopped until the clock is synchronized again.

The ETR support is activated via two sysfs attributes; run the following commands as root:

echo 1 > /sys/devices/system/etr/etr0/online
echo 1 > /sys/devices/system/etr/etr1/online