Error SnapshotNotStarted prevents the backup to go through

[asitemade4u]

Hi, and thank you for the tool and its outstanding documentation. I just began to test it (version 0.56) and am hitting a snag: none of my raw-image based domains will allow a snapshot:

virt_backup.exceptions.SnapshotNotStarted: snapshot not started
al9pis: Backup started
libvirt: QEMU Driver error : unsupported configuration: nothing selected for snapshot
('al9pis: snapshot with Quiesce required, but failed. It can be due to the lack of a QEMU guest agent running inside the VM. Retrying without Quiesce.',)
libvirt: QEMU Driver error : unsupported configuration: nothing selected for snapshot
Error with domain al9pis: snapshot not started
snapshot not started
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/virt_backup/backups/snapshot.py", line 121, in external_snapshot
    return self.dom.snapshotCreateXML(snap_xml, flags)
  File "/usr/lib64/python3.9/site-packages/libvirt.py", line 3141, in snapshotCreateXML
    raise libvirtError('virDomainSnapshotCreateXML() failed')
libvirt.libvirtError: unsupported configuration: nothing selected for snapshot

I guess I have something wrong in my config.yml file (which I based on the Getting Started example).

Or maybe the snapshot feature is not handled well on raw image files?

I attach the config.yml file for reference:

---

########################
#### Global options ####
########################

## Be more verbose ##
debug: False

## How many threads (simultaneous backups) to run. Use 0 to use all CPU threads
## detected, 1 to disable multitheading for backups, or the number of threads
## wanted. Default: 1
threads: 1


############################
#### Libvirt connection ####
############################

## Libvirt URI ##
uri: "qemu:///system"

## Libvirt authentication, if needed ##
#username:
#passphrase:


#######################
#### Backup groups ####
#######################
## Define default options for all groups. ##
## Here we set the retention parameters for each VM when calling `virt-backup clean`.
default:
  hourly: 1
  daily: 4
  weekly: 2
  monthly: 5
  yearly: 1

## Groups definition ##
groups:
  ## Group name ##
  all:
    ## Backup directory ##
    target: /zfs212/vms-bkp

    ## Use ZSTD compression, configured at lvl 6
    packager: zstd
    packager_opts:
      compression_lvl: 6

    ## When doing `virt-backup backup` without specifying any group, only
    ## groups with the autostart option enabled will be backup.
    autostart: True

    ## Enable the Libvirt Quiesce option when taking the external snapshots.
    quiesce: True

    ## Hosts definition ##
    hosts:
      ## Will backup everything.
      - "r:.*"

Please help, Stephen