I tried to override the root volume but got a quota error, i also tried with the format suggested in Error modifying LXD VM devices for stateful snapshoting - #3 by mezobari but had the same result.
root@s26001:~# incus config device override llama-cpp-server root size=33GB
Error: Failed to update device "root": Failed to run: btrfs qgroup limit 33000000000 0/258 /var/lib/incus/storage-pools/default/containers/llama-cpp-server: exit status 1 (ERROR: unable to limit requested quota group: Disk quota exceeded)
root@s26001:~# incus config device override llama-cpp-server root size.state=33GB
Error: Failed to update device "root": Failed to run: btrfs qgroup limit 30000000000 0/258 /var/lib/incus/storage-pools/default/containers/llama-cpp-server: exit status 1 (ERROR: unable to limit requested quota group: Disk quota exceeded)
I had a look in system journal but don’t see any messages logged at that time.
In case the issue with btrfs was kernel version specific I rebooted from 6.12.101+deb13-amd64 into 6.12.73+deb13-amd64 but the disk quota issue persists - for root and incus
root@s26001:~# incus config device override llama-cpp-server root size.state=33GB
Error: Failed to write backup file: Failed to create file "/var/lib/incus/containers/llama-cpp-server/backup.yaml": openat backup.yaml: disk quota exceeded
root@s26001:~# mkdir /var/lib/incus/containers/llama-cpp-server/credentials
mkdir: cannot create directory ‘/var/lib/incus/containers/llama-cpp-server/credentials’: Disk quota exceeded