[Bug 1579130] Re: need to support systemd.link renaming of devices in container

Martin Pitt martin.pitt at ubuntu.com
Sat May 7 01:26:19 UTC 2016

** Changed in: systemd (Ubuntu)
       Status: New => Triaged

** Changed in: systemd (Ubuntu)
     Assignee: (unassigned) => Martin Pitt (pitti)

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  need to support systemd.link renaming of devices in container

Status in cloud-init package in Ubuntu:
Status in systemd package in Ubuntu:

Bug description:
  We're interested in supporting network configuration of lxc containers
  via maas/cloud-init yaml format.

  The end goal is to do:
  $ lxc init xenial x1
  $ ncpath=/var/lib/cloud/seed/nocloud-net/network-config
  $ sudo tee /var/lib/lxd/containers/x1/rootfs/$ncpath <<EOF
  version: 1
    - type: physical
      mac_address: "00:16:3e:3b:01:7a"
      name: foo2
        - type: dhcp
          control: auto

  $ lxc start x1
  $ lxc exec x1 /bin/bash

  From inside we expect to have a device named 'foo2' at this point that
  has dhcp'd.

  We've run into a number of issues with this.
   a.) we don't get coldplug events for devices in a container, so writing systemd.link (or 70-persistent-net.rules style udev rules files) wont "just work" to apply the name changes.

   b.) systemd.link does rename devices that have been renamed previously, and all lxd instance devices are renamed (from the kernel returned veth<random> into 'eth0').
   That is implemented by check of /sys/devices/virtual/net/eth0/name_assign_type . Value of 4 means renamed.

   c.) systemd.link will not attempt to rename a device that does not have a driver.
     To see that run: udevadm test-builtin net_setup_link /sys/class/net/eth0

  To force these systemd.link files to run in spite of 'b' on kvm guests
  or bare metal, we have found that unbind and rebind of the device will
  clear the state and rename would occur.  that can be done as shown in
  init/+bug/1577844/comments/3 but since there is no 'driver' we cannot
  unbind and rebind veth devices.

  Ultimately, we want to allow cloud-init to configure the system once
  and then let renaming on reboots not require involvement of cloud-
  init.  And at the moment the ideal way to affect that would be through
  systemd.link files such as /etc/systemd/network/50-cloud-init-

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: udev 229-4ubuntu4
  ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
  Uname: Linux 4.4.0-21-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  Date: Fri May  6 15:42:52 2016
  MachineType: LENOVO 33672B7
   PATH=(custom, no user)
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-21-generic.efi.signed root=UUID=19ac97d5-6973-4193-9a09-2e6bbfa38262 ro quiet splash vt.handoff=7
  SourcePackage: systemd
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 12/18/2013
  dmi.bios.vendor: LENOVO
  dmi.bios.version: G8ET96WW (2.56 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 33672B7
  dmi.board.vendor: LENOVO
  dmi.board.version: Not Defined
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Not Available
  dmi.modalias: dmi:bvnLENOVO:bvrG8ET96WW(2.56):bd12/18/2013:svnLENOVO:pn33672B7:pvrThinkPadX131e:rvnLENOVO:rn33672B7:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable:
  dmi.product.name: 33672B7
  dmi.product.version: ThinkPad X131e
  dmi.sys.vendor: LENOVO

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