VDI.snapshot_of issues
A race condition during VM.revert could inadvertently corrupt the snapshot_of field of other VDI objects. XAPI received a fix for this issue in the version xapi-26.1.21-1.1, but the fallout from previously corrupted database entries can lead to issues, since some API users can then interpret the non-snapshot VDI as if it was a snapshot VDI. A helper script is provided to fix xapi databases with incongruent snapshot metadata.
You can check if you were affected by this issue by running the helper script with the dry-run option. If it does not list any VDIs with wrong metadata, then you likely were not affected.
If you are still experiencing new wrong modifications of the VDI.snapshot_of field after the above update and after fixing any remaining corrupted database entries, please let our support know so that we can explore additional fixes.
The script requires XCP-ng 8.3 or later. It refuses to run on earlier versions because they do not produce correct results. There is no equivalent for XCP-ng 8.2, which has reached end of life. Upgrade to a supported release to use this script.
The script temporarily disables HA and stops xapi to apply the changes to the database. This means that the pool is not running operations like handling backups, migrating, starting or stopping VMs, and HA is disabled during the operation. To check for issues in the pool without stopping xapi and rewriting the database, the dry-run option can be used:
# ./snapshot-fixer.py dry-run INFO:root:Regenerating database... INFO:root:The VDI 38dd4f0e-6d0e-46e1-bb1a-980ec3d3efd2 has OpaqueRef:3664c45a-2943-52b6-529b-693e8275130b as its "snapshot_of" value, changing to null.
The script needs to be run on the master host of the affected pool:
# ./snapshot-fixer.py rewrite INFO:root:Check HA... INFO:root:Shutting down xapi... INFO:root:Regenerating database... INFO:root:The VDI 38dd4f0e-6d0e-46e1-bb1a-980ec3d3efd2 has OpaqueRef:3664c45a-2943-52b6-529b-693e8275130b as its "snapshot_of" value, changing to null. INFO:root:Writing database to /var/lib/xcp/state.db INFO:root:Starting up xapi...
In the unlikely case the script corrupts the database, the script provides the restore-backup option to restore the database from the backup (which is automatically generated on every script invocation).