Snapper on SUSE Linux Enterprise Server is preconfigured 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. Timeline snapshots for the root partition need to be enabled for this purpose—see Disabling/Enabling Snapshots for details.
By default, automatic snapshots as described above are configured for the root partition and its subvolumes. To make snapshots available for other partitions such as /home for example, you can create custom configurations.
IMPORTANT: Undoing Changes Compared to Rollback
When working with snapshots to restore data, it is important to know that there are two fundamentally different scenarios Snapper can handle:
When undoing changes as described in the following, two snapshots are being compared and the changes between these two snapshots are made undone. Using this method also allows to explicitly select the files that should be restored.
When doing rollbacks as described in Section 7.3, System Rollback by Booting from Snapshots, the system is reset to the state at which the snapshot was taken.
When undoing changes, it is also possible to compare a snapshot against the current system. When restoring all files from such a comparison, this will have the same result as doing a rollback. However, using the method described in Section 7.3, System Rollback by Booting from Snapshots for rollbacks should be preferred, since it is faster and allows you to review the system before doing the rollback.
WARNING: Data Consistency
There is no mechanism to ensure data consistency when creating a snapshot. Whenever a file (for example, a database) is written at the same time as the snapshot is being created, it will result in a corrupted or partly written file. Restoring such a file will cause problems. Furthermore, some system files such as /etc/mtab must never be restored. Therefore it is strongly recommended to always closely review the list of changed files and their diffs. Only restore files that really belong to the action you want to revert.
If you set up the root partition with Btrfs during the
installation, Snapper—preconfigured 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).
Undoing Changes Using the YaST Snapper Module
Start the yast2 snapper.module from the section in YaST or by entering
Make sureis set to . This is always the case unless you have manually added own Snapper configurations.
Choose a pair of pre- and post-snapshots from the list. Both, YaST and Zypper snapshot pairs are of the type zypp(y2base) in the ; Zypper snapshots are labeled zypp(zypper).. YaST snapshots are labeled as
Clickto open the list of files that differ between the two snapshots.
Review the list of files. To display a
diff between the
pre- and post-version of a file, select it from the list.
To restore one or more files, select the relevant files or directories by activating the respective check box. Clickand confirm the action by clicking .
To restore a single file, activate its diff view by clicking its name. Clickand confirm your choice with .
Undoing Changes Using the snapper Command
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 ; Zypper snapshots are labeled zypp(zypper).
tux > sudo snapper list -t pre-post Pre # | Post # | Pre Date | Post Date | Description ------+--------+-------------------------------+-------------------------------+-------------- 311 | 312 | Tue 06 May 2014 14:05:46 CEST | Tue 06 May 2014 14:05:52 CEST | zypp(y2base) 340 | 341 | Wed 07 May 2014 16:15:10 CEST | Wed 07 May 2014 16:15:16 CEST | zypp(zypper) 342 | 343 | Wed 07 May 2014 16:20:38 CEST | Wed 07 May 2014 16:20:42 CEST | zypp(y2base) 344 | 345 | Wed 07 May 2014 16:21:23 CEST | Wed 07 May 2014 16:21:24 CEST | zypp(zypper) 346 | 347 | Wed 07 May 2014 16:41:06 CEST | Wed 07 May 2014 16:41:10 CEST | zypp(y2base) 348 | 349 | Wed 07 May 2014 16:44:50 CEST | Wed 07 May 2014 16:44:53 CEST | zypp(y2base) 350 | 351 | Wed 07 May 2014 16:46:27 CEST | Wed 07 May 2014 16:46:38 CEST | zypp(y2base)
Get a list of changed files for a snapshot pair with snapper status PRE..POST. Files with content changes are marked with , files that have been added are marked with and deleted files are marked with .
tux > sudo snapper status 350..351 +..... /usr/share/doc/packages/mikachan-fonts +..... /usr/share/doc/packages/mikachan-fonts/COPYING +..... /usr/share/doc/packages/mikachan-fonts/dl.html c..... /usr/share/fonts/truetype/fonts.dir c..... /usr/share/fonts/truetype/fonts.scale +..... /usr/share/fonts/truetype/みかちゃん-p.ttf +..... /usr/share/fonts/truetype/みかちゃん-pb.ttf +..... /usr/share/fonts/truetype/みかちゃん-ps.ttf +..... /usr/share/fonts/truetype/みかちゃん.ttf c..... /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4 c..... /var/lib/rpm/Basenames c..... /var/lib/rpm/Dirnames 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/Requirename c..... /var/lib/rpm/Sha1header c..... /var/lib/rpm/Sigmd5
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.
tux > sudo snapper diff 350..351 /usr/share/fonts/truetype/fonts.scale --- /.snapshots/350/snapshot/usr/share/fonts/truetype/fonts.scale 2014-04-23 15:58:57.000000000 +0200 +++ /.snapshots/351/snapshot/usr/share/fonts/truetype/fonts.scale 2014-05-07 16:46:31.000000000 +0200 @@ -1,4 +1,4 @@ -1174 +1486 ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso10646-1 ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso8859-1 [...]
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.
tux > sudo snapper -v undochange 350..351 create:0 modify:13 delete:7 undoing change... deleting /usr/share/doc/packages/mikachan-fonts deleting /usr/share/doc/packages/mikachan-fonts/COPYING deleting /usr/share/doc/packages/mikachan-fonts/dl.html deleting /usr/share/fonts/truetype/みかちゃん-p.ttf deleting /usr/share/fonts/truetype/みかちゃん-pb.ttf deleting /usr/share/fonts/truetype/みかちゃん-ps.ttf deleting /usr/share/fonts/truetype/みかちゃん.ttf modifying /usr/share/fonts/truetype/fonts.dir modifying /usr/share/fonts/truetype/fonts.scale modifying /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4 modifying /var/lib/rpm/Basenames modifying /var/lib/rpm/Dirnames 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/Requirename modifying /var/lib/rpm/Sha1header modifying /var/lib/rpm/Sigmd5 undoing change done
WARNING: Reverting User Additions
Reverting user additions via undoing changes with Snapper is not recommended. Since certain directories are excluded from snapshots, files belonging to these users will remain in the file system. If a user with the same user ID as a deleted user is created, this user will inherit the files. Therefore it is strongly recommended to use the YaSTtool to remove users.
Apart from the installation and administration snapshots, Snapper creates timeline snapshots. You can use these backup snapshots to restore files that have accidentally been deleted or to restore a previous version of a file. By using Snapper's diff feature you can also find out which modifications have been made at a certain point of time.
Being able to restore files is especially interesting for data, which may reside on subvolumes or partitions for which snapshots are not taken by default. To be able to restore files from home directories, for example, create a separate Snapper configuration for /home doing automatic timeline snapshots. See Section 7.4, Creating and Modifying Snapper Configurations for instructions.
WARNING: Restoring Files Compared to Rollback
Snapshots taken from the root file system (defined by Snapper's root configuration), can be used to do a system rollback. The recommended way to do such a rollback is to boot from the snapshot and then perform the rollback. See Section 7.3, System Rollback by Booting from Snapshots for details.
Performing a rollback would also be possible by restoring all files from a root file system snapshot as described below. However, this is not recommended. You may restore single files, for example a configuration file from the /etc directory, but not the complete list of files from the snapshot.
This restriction only affects snapshots taken from the root file system!
Restoring Files Using the YaST Snapper Module
Start the yast2 snapper.module from the section in YaST or by entering
Choose thefrom which to choose a snapshot.
Select a timeline snapshot from which to restore a file and choose. Timeline snapshots are of the type with a description value of .
Select a file from the text box by clicking the file name. The difference between the snapshot version and the current system is shown. Activate the check box to select the file for restore. Do so for all files you want to restore.
Clickand confirm the action by clicking .
Restoring Files Using the snapper Command
Get a list of timeline snapshots for a specific configuration by running the following command:
tux > sudo snapper -c CONFIG list -t single | grep timeline
CONFIG needs to be replaced by an existing Snapper configuration. Use snapper list-configs to display a list.
Get a list of changed files for a given snapshot by running the following command:
tux > sudo snapper -c CONFIG status SNAPSHOT_ID..0
Replace SNAPSHOT_ID by the ID for the snapshot from which you want to restore the file(s).
Optionally list the differences between the current file version and the one from the snapshot by running
tux > sudo snapper -c CONFIG diff SNAPSHOT_ID..0 FILE NAME
If you do not specify <FILE NAME>, the difference for all files are shown.
To restore one or more files, run
tux > sudo snapper -c CONFIG -v undochange SNAPSHOT_ID..0 FILENAME1 FILENAME2
If you do not specify file names, all changed files will be restored.