Re: [pve-devel] [PATCH qemu-server] migration: prohibit renaming cloud-init drive

["Daniel Kral" <d.kral@proxmox.com>]

On Mon Dec 1, 2025 at 2:51 PM CET, Fiona Ebner wrote:
> Usually, disks are allowed to be renamed during migration if there is
> a naming conflict caused by a left-over disk on the target. However,
> the type of the cloud-init disk is encoded in its name, so it must not
> be renamed or it cannot be recognized as a cloud-init disk anymore, as
> reported in the community forum [0].
>
> [0]: https://forum.proxmox.com/threads/167767/

A user in the community forum [1] reported that if a VM is moved to
another node during a fence recovery, the VM will fail to migrate back,
e.g., if a node affinity rule prioritizes the previous node.

This patch is correct to not allow renaming cloudinit images, but I
wonder if it would be a reasonable idea to allow overriding existing
cloudinit images on the target node as these are auto-generated?

That would probably need a `--allow-override` flag for pvesm, which
would require that the target host can understand the parameter though.

[1] https://forum.proxmox.com/threads/181516/

>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
>  src/PVE/QemuMigrate.pm | 6 +++++-
>  src/PVE/QemuServer.pm  | 3 +++
>  2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/src/PVE/QemuMigrate.pm b/src/PVE/QemuMigrate.pm
> index 8fa84080..a1d7471c 100644
> --- a/src/PVE/QemuMigrate.pm
> +++ b/src/PVE/QemuMigrate.pm
> @@ -439,6 +439,7 @@ sub scan_local_volumes {
>                  PVE::Storage::volume_size_info($storecfg, $volid);
>  
>              $local_volumes->{$volid}->{is_vmstate} = $attr->{is_vmstate} ? 1 : 0;
> +            $local_volumes->{$volid}->{is_cloudinit} = $attr->{is_cloudinit} ? 1 : 0;
>  
>              $local_volumes->{$volid}->{drivename} = $attr->{drivename}
>                  if $attr->{drivename};
> @@ -725,11 +726,14 @@ sub sync_offline_local_volumes {
>              my $bwlimit = $local_volumes->{$volid}->{bwlimit};
>              $bwlimit = $bwlimit * 1024 if defined($bwlimit); # storage_migrate uses bps
>  
> +            my $preserve_name =
> +                $local_volumes->{$volid}->{is_vmstate} || $local_volumes->{$volid}->{is_cloudinit};
> +
>              my $storage_migrate_opts = {
>                  'ratelimit_bps' => $bwlimit,
>                  'insecure' => $opts->{migration_type} eq 'insecure',
>                  'with_snapshots' => $local_volumes->{$volid}->{snapshots},
> -                'allow_rename' => !$local_volumes->{$volid}->{is_vmstate},
> +                'allow_rename' => !$preserve_name,
>              };
>  
>              my $logfunc = sub { $self->log('info', $_[0]); };
> diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
> index a7fbec14..70faab62 100644
> --- a/src/PVE/QemuServer.pm
> +++ b/src/PVE/QemuServer.pm
> @@ -4502,6 +4502,9 @@ sub foreach_volid {
>          $volhash->{$volid}->{cdrom} //= 1;
>          $volhash->{$volid}->{cdrom} = 0 if !drive_is_cdrom($drive);
>  
> +        $volhash->{$volid}->{is_cloudinit} //= 0;
> +        $volhash->{$volid}->{is_cloudinit} = 1 if drive_is_cloudinit($drive);
> +
>          my $replicate = $drive->{replicate} // 1;
>          $volhash->{$volid}->{replicate} //= 0;
>          $volhash->{$volid}->{replicate} = 1 if $replicate;