Updating to SLE 15 SP3 breaks udev network when cloning machines in the XEN environment

This document (000020542) is provided subject to the disclaimer at the end of this document.

Environment

This applies to XEN environments and others where a clone might be used to create new servers.

Situation

Changes to the handling of udev rules for networking in systemd causes the network to be broken when a system is cloned.

These rule changes to udev were inserted in the register interfaces in "/etc/udev/rules.d/70-persistent-net.rules" for XEN. This causes the XEN virtual network cards, which previously were not registered in /etc/udev/rules.d/70-persistent-net.rules, to now be registered.

Resolution

The workaround is to prevent the use of 70-persistent-net.rules when cloning VMs by blocking it by making it a symlink to /dev/null. (ie: ln -sf /dev/null "70-persistent-net.rules"). It can be restored to a file after clones are completed.
 

Cause

The change that caused this problem was introduced in mid-year 2021 as a major systemd version change. The change is located in systemd-246.10.xxxx update for SLE 15 SP3 (SLES and SLED). Previous versions of systemd did not contain this change. 

For SLE 15 SP2 and SLE 12 SP5 (SLES and SLED) the change was made to maintenance release systemd-234-24.87.  Release systemd-234-24.82 and earlier do not have the change that causes the problem.

The change that has caused this issue is the preferred way going forward for the systemd upstream project. It is important that we stay in-step with the upstream code base for obvious reasons. 
 

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:000020542
  • Creation Date: 13-Jan-2022
  • Modified Date:18-Jan-2022
    • SUSE Linux Enterprise Desktop
    • SUSE Linux Enterprise Server

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