For VMs under ceph.rbd.backend=librbd sgdisk fails

[jealouscloud]

Is there an existing issue for this?

• There is no existing issue for this bug

Is this happening on an up to date version of Incus?

• This is happening on a supported version of Incus

Incus system details

config:
  cluster.https_address: 10.0.56.2:8443
  core.https_address: 0.0.0.0:8443
  core.metrics_address: :8444
api_extensions_count: 553
api_status: stable
api_version: "1.0"
auth: trusted
public: false
auth_methods:
  - tls
auth_user_name: root
auth_user_method: unix
environment:
  addresses:
    - 198.46.86.216:8443
    - 10.0.55.2:8443
    - 10.0.55.250:8443
    - 10.0.56.2:8443
  architectures:
    - x86_64
    - i686
  certificate: ""
  certificate_fingerprint: b8c03c7315edac5c3bed3ba3b5f8692bf6114291c719ee12bed8ca3d3d8511af
  driver: lxc | qemu
  driver_version: 7.0.0 | 11.1.1
  firewall: nftables
  kernel: Linux
  kernel_architecture: x86_64
  kernel_features: {}
  kernel_version: 6.1.0-52-amd64
  lxc_features: {}
  os_name: Debian GNU/Linux
  os_version: "12"
  project: default
  server: incus
  server_clustered: true
  server_event_mode: full-mesh
  server_name: ash-t3x-pro-hci1-a1
  server_pid: 1098584
  server_version: "7.4"
  storage: ceph
  storage_version: 20.2.4
  storage_supported_drivers:
    - name: truenas
      version: 0.7.7
      remote: true
    - name: cephfs
      version: 20.2.4
      remote: true
    - name: dir
      version: "1"
      remote: false
    - name: lvm
      version: 2.03.16(2) (2022-05-18) / 1.02.185 (2022-05-18) / 4.47.0
      remote: false
    - name: ceph
      version: 20.2.4
      remote: true
    - name: cephobject
      version: 20.2.4
      remote: true

Instance details

No response

Instance log

No response

Current behavior

Launching a VM on ceph with ceph.rbd.backend=librbd fails to create the VM

Expected behavior

Launching a VM on ceph with ceph.rbd.backend=librbd creates a VM successfully

Steps to reproduce

1. Setup ceph cluster and add storage to cluster. This was done on Daily build 1:0~debian12~202609041454 which contains a fix for ceph.rbd.backend=librbd fails to setup NBD #3952
2. incus storage set $cluster ceph.rbd.backend=librbd

[root@ash-t3x-pro-hci1-a1 ~]# incus launch images:debian/12 demo-vm --vm --storage fast
Launching demo-vm
Error: Failed instance creation: Failed creating instance from image: Failed to run: /usr/sbin/sgdisk --move-second-header /dev/nbd0: exit status 4 (Unable to save backup partition table! Perhaps the 'e' option on the experts'
menu will resolve this problem.
Warning! An error was reported when writing the partition table! This error
MIGHT be harmless, or the disk might be damaged! Checking it is advisable.)

There may be a gap in testing for the new ceph.rbd.backend since #3952 is a very similar bug and this feature just landed recently.