Unable to Back up Locked VM (code 1970)
Status: Coming soon
Situation
A backup plan completes with the following warning message: Unable to back up locked VM. Proxmox places a lock on a VM during operations such as backup, snapshot creation, migration, or cloning. If a previous operation crashed or timed out, the lock may remain and prevent new backup jobs from starting.. The message also contains a list of locked VMs.
Cause
Locked VMs cannot be backed up.
The backup service performs multiple retry attempts for up to 5 minutes, but the listed VMs remain locked during this time and are skipped.
Solutions
- Wait for the operation to complete. If a legitimate operation is still running, allow it to finish. You can verify running tasks in the Proxmox Web Console under Datacenter > Tasks.
- Unlock manually: If no operation is currently running, you can remove the lock manually using the following command:
qm unlock <Proxmox_VM_ID>
Where '<Proxmox_VM_ID>' stands for the Proxmox VM ID.
Warning: Do not unlock the VM while an operation is in progress, as this may corrupt the disk or snapshot state.
Troubleshooting Checklist
Before unlocking a VM manually, verify the following:
1. Check running tasks
Open the Proxmox Web Console and navigate to Datacenter → Tasks. Confirm that no backup, snapshot, migration, or clone operation is currently running for the VM.
2. Check VM lock status
Run the following command on the Proxmox node to verify if the VM is locked:
qm config <Proxmox_VM_ID>
Look for the lock: parameter in the output.
3. Verify cluster tasks (if using a cluster)
Make sure the operation is not running on another node in the cluster.
4. Check for stuck backup jobs
Ensure that no previous backup process is still running or hanging.
5. Unlock the VM only if safe
If no operation is running and the VM remains locked, unlock it manually: