Comment 19 for bug 1770082

Note, that uvt-kvm is going to use cloud-init; how are you making
sure that cloud-init isn't doing the rename itself?
Xenial by default doesn't use netplan; it still uses eni; the network
configuration generation in cloud-init using eni
does create a 70-persistent-net.rules file that handles renames on
subsequent reboots; in a netplan world (bionic)
the .link file is meant to be the equivalent of a .rules file.

I've not attempted to determine if systemd-udev in bionic would
respect renames from .rules file; it certainly seems
odd to have .rules files allow renames independent of name_assign_type
value where .link files do.

On Tue, May 15, 2018 at 12:29 PM, Daniel Axtens
<email address hidden> wrote:
> Hi Ryan,
>
> [Journal Output]
> Attached.
>
> [Reproducer]
> uvt-kvm create xenial-test release=xenial arch=amd64
> virsh edit xenial-test # change network interface pci slot: s/0x03/0x10/
> virsh destroy xenial-test
> virsh start xenial-test
> uvt-kvm ssh xenial-test
> dmesg|grep rename
> [ 2.790623] virtio_net virtio3 ens16: renamed from eth0
> [ 6.048520] virtio_net virtio3 ens3: renamed from ens16
>
> [Analysis]
> I've been working on this a lot, and I think I have the cause of the difference.
>
> In udev-events.c, udev_execute_rules will _forcibly_ rename a device
> with via a netlink message if there is a matching rule that sets a name.
> Under Xenial, there *is* a matching rule, in 70-persistent-net.rules, so
> this forces a rename. This rename will occur even if the device already
> has a name, and therefore even if the rules file isn't in the initramfs.
>
> Under Bionic, this rules file doesn't exist, there is a .link file
> instead. Unfortunately, a name in a .link file will only take effect if
> the device hasn't been renamed - because of the renaming in initrd, this
> means that a link file that is not present in the initrd will never be
> able to cause a rename.
>
> [Solutions]
> There are a couple of ways we could fix this that come to mind:
>
> - make netplan generate a file in /run/udev/rules.d for each device
> - make systemd rename devices from a link file even if they've been renamed
>
> My preference is the first, but I'm open to anything we can get
> upstream.
>
> Thanks again.
>
> Regards,
> Daniel
>
> ** Attachment added: "journalctl -b output on Xenial VM with multiple renames"
> https://bugs.launchpad.net/netplan/+bug/1770082/+attachment/5139894/+files/journalctl-b.txt
>
> --
> You received this bug notification because you are subscribed to
> netplan.
> Matching subscriptions: netplan
> https://bugs.launchpad.net/bugs/1770082
>
> Title:
> systemd-networkd not renaming devices on boot
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/netplan/+bug/1770082/+subscriptions