[Bug 1682437] Re: udev does not preserve virtio interface names on s390x upgrades

[Dimitri John Ledkov]

** Description changed:

+ [Impact]
+ 
+  * Upgrading s390x, kvm/qemu instances from yakkety to zesty results in a change of network interface names (e.g. from eth0 to stable/predictable bus_id name enc3, just like on z/VM and LPAR).
+  * This obviously results in loss of network connectivity as /etc/network/interfaces no longer matches the network interface names configured by systemd.
+  * The proposal is to generate udev rules on upgrade to preserve active interface names, in a very similar fashion to the no longer in use net-persistent-name generator.
+ 
+ [Test Case]
+ 
+  * Install zesty from scratch in kvm/qemu, network interfaces should use enc* names.
+  * Install yakkety, upgrade to zesty, network intefaces should use eth* names after upgrade and reboot.
+ 
+ [Regression Potential]
+ 
+  * This solution is similar to previous upgrades to stable networking
+ names for other types of network interfaces. This will make upgraded
+ systems look different from freshly installed systems. For users aiming
+ to have homogenious environments it is recommended to remove
+ /etc/udev/rules.d/70-persistent-net.rules and readjust
+ networking/daemon/firewall configurations to the new stable names enc*.
+ 
+ [Other Info]
+  
+  * Original bug report filed in debian.
+ 
  Package: udev
  Version: 232-20
  Severity: important
  
  Dear Maintainer,
  
  systemd 232-20 introduce the patch to generate stable interface names
  for virtio network interfaces on s390x. This is a good thing, and
  those names should be used for new installations.
  
  However, when upgrading existing virtual machines installations the
  new udev causes interfaces to be renamed from eth0 -> enc1 thus
  breaking networking configuration and possibly other configs
  (e.g. daemons, firewalls etc).
  
  Therefore on upgrade (but not clean installs) something like
  persistent net rules should be generated to preserve ethX interface
  names and thus not break networking configuration.
  
  I will attach a proposed patch to achieve this shortly for review.
  
  It is important to fix this in stretch such that upgrades to stretch
  are flawless.

** Also affects: systemd (Ubuntu Zesty)
   Importance: High
     Assignee: Dimitri John Ledkov (xnox)
       Status: Triaged

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https://bugs.launchpad.net/bugs/1682437

Title:
  udev does not preserve virtio interface names on s390x upgrades

Status in Release Notes for Ubuntu:
  Fix Released
Status in systemd package in Ubuntu:
  Triaged
Status in systemd source package in Zesty:
  Triaged

Bug description:
  [Impact]

   * Upgrading s390x, kvm/qemu instances from yakkety to zesty results in a change of network interface names (e.g. from eth0 to stable/predictable bus_id name enc3, just like on z/VM and LPAR).
   * This obviously results in loss of network connectivity as /etc/network/interfaces no longer matches the network interface names configured by systemd.
   * The proposal is to generate udev rules on upgrade to preserve active interface names, in a very similar fashion to the no longer in use net-persistent-name generator.

  [Test Case]

   * Install zesty from scratch in kvm/qemu, network interfaces should use enc* names.
   * Install yakkety, upgrade to zesty, network intefaces should use eth* names after upgrade and reboot.

  [Regression Potential]

   * This solution is similar to previous upgrades to stable networking
  names for other types of network interfaces. This will make upgraded
  systems look different from freshly installed systems. For users
  aiming to have homogenious environments it is recommended to remove
  /etc/udev/rules.d/70-persistent-net.rules and readjust
  networking/daemon/firewall configurations to the new stable names
  enc*.

  [Other Info]
   
   * Original bug report filed in debian.

  Package: udev
  Version: 232-20
  Severity: important

  Dear Maintainer,

  systemd 232-20 introduce the patch to generate stable interface names
  for virtio network interfaces on s390x. This is a good thing, and
  those names should be used for new installations.

  However, when upgrading existing virtual machines installations the
  new udev causes interfaces to be renamed from eth0 -> enc1 thus
  breaking networking configuration and possibly other configs
  (e.g. daemons, firewalls etc).

  Therefore on upgrade (but not clean installs) something like
  persistent net rules should be generated to preserve ethX interface
  names and thus not break networking configuration.

  I will attach a proposed patch to achieve this shortly for review.

  It is important to fix this in stretch such that upgrades to stretch
  are flawless.

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