[PATCH container] api: template: allow creating template from ct with disk on LVM

[PATCH container] api: template: allow creating template from ct with disk on LVM

[Lukas Sichert]

Currently, in the UI, one can create a template from a VM with a disk on
LVM storage, but not from a container. This is because the LVM plugin
does not have the functionality to create base images from disks
implemented. While the system simply skips this function for VMs, it
throws an error and aborts for LXC containers.

To allow converting to a template, skip the volumes where the required
functionality is not present by exiting early instead of aborting.

Signed-off-by: Lukas Sichert <l.sichert@proxmox.com>
---
 src/PVE/LXC.pm | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index caba952..e77d208 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -1613,17 +1613,7 @@ sub template_create {
 
             my $volid = $mountpoint->{volume};
 
-            die "Template feature is not available for '$volid'\n"
-                if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
-        },
-    );
-
-    PVE::LXC::Config->foreach_volume(
-        $conf,
-        sub {
-            my ($ms, $mountpoint) = @_;
-
-            my $volid = $mountpoint->{volume};
+            return if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
 
             PVE::Storage::activate_volumes($storecfg, [$volid]);
 
-- 
2.47.3

Re: [PATCH container] api: template: allow creating template from ct with disk on LVM

[Fiona Ebner]

Am 12.03.26 um 7:26 PM schrieb Lukas Sichert:
> Currently, in the UI, one can create a template from a VM with a disk on
> LVM storage, but not from a container. This is because the LVM plugin
> does not have the functionality to create base images from disks
> implemented. While the system simply skips this function for VMs, it
> throws an error and aborts for LXC containers.
> 
> To allow converting to a template, skip the volumes where the required
> functionality is not present by exiting early instead of aborting.
> 

I feel like we should properly implement the feature the LVM plugin
instead and maybe start requiring the feature for VMs with the next
major version too, but not super important. The implementation for the
LVM plugin can be similar to what is done for LVM-thin, i.e. rename and
set readonly and activationskip flags.

> Signed-off-by: Lukas Sichert <l.sichert@proxmox.com>
> ---
>  src/PVE/LXC.pm | 12 +-----------
>  1 file changed, 1 insertion(+), 11 deletions(-)
> 
> diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
> index caba952..e77d208 100644
> --- a/src/PVE/LXC.pm
> +++ b/src/PVE/LXC.pm
> @@ -1613,17 +1613,7 @@ sub template_create {
>  
>              my $volid = $mountpoint->{volume};
>  
> -            die "Template feature is not available for '$volid'\n"
> -                if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
> -        },
> -    );
> -
> -    PVE::LXC::Config->foreach_volume(
> -        $conf,
> -        sub {
> -            my ($ms, $mountpoint) = @_;
> -
> -            my $volid = $mountpoint->{volume};
> +            return if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
>  
>              PVE::Storage::activate_volumes($storecfg, [$volid]);
>  

Re: [PATCH container] api: template: allow creating template from ct with disk on LVM

[Elias Huhsovitz]

I agree with @Fiona [1], but IMO this a good intermediate solution and I
don't see any downside in applying this.

The current state is somewhat annoying and this patch makes the
behaviour more consistent with VM equivalent function.

I gave this a quick test with a container containing 2 volumes:
- Root Disk: lvm-thin
- mp0: lvm

Creating the template worked without issues. 

When attempting to create a linked clone of the template, the user is
correctly stopped with an error.

Creating a full clone worked without any issues.

Reviewed-by: Elias Huhsovitz <e.huhsovitz@proxmox.com>
Tested-by: Elias Huhsovitz <e.huhsovitz@proxmox.com>

[1] https://lore.proxmox.com/pve-devel/328e1266-003a-42fd-bfea-2801b5afb88d@proxmox.com/

On Thu Mar 12, 2026 at 7:27 PM CET, Lukas Sichert wrote:
> Currently, in the UI, one can create a template from a VM with a disk on
> LVM storage, but not from a container. This is because the LVM plugin
> does not have the functionality to create base images from disks
> implemented. While the system simply skips this function for VMs, it
> throws an error and aborts for LXC containers.
>
> To allow converting to a template, skip the volumes where the required
> functionality is not present by exiting early instead of aborting.
>
> Signed-off-by: Lukas Sichert <l.sichert@proxmox.com>
> ---
>  src/PVE/LXC.pm | 12 +-----------
>  1 file changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
> index caba952..e77d208 100644
> --- a/src/PVE/LXC.pm
> +++ b/src/PVE/LXC.pm
> @@ -1613,17 +1613,7 @@ sub template_create {
>  
>              my $volid = $mountpoint->{volume};
>  
> -            die "Template feature is not available for '$volid'\n"
> -                if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
> -        },
> -    );
> -
> -    PVE::LXC::Config->foreach_volume(
> -        $conf,
> -        sub {
> -            my ($ms, $mountpoint) = @_;
> -
> -            my $volid = $mountpoint->{volume};
> +            return if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
>  
>              PVE::Storage::activate_volumes($storecfg, [$volid]);
>