Proxmox VMs may be getting locked due to ongoing tasks like backups or migrations, resource allocation conflicts, storage issues like corruption, networking problems, or manual intervention for maintenance or troubleshooting.

When you encounter a situation where a virtual machine is locked due to an error or conflict, preventing normal operation or management tasks like starting, stopping, or migrating the VM. This command releases the lock, allowing you to resolve the issue and regain control over the VM:

  # qm unlock VM-ID
    

This may not always work, and the command may fail with following output:

  trying to acquire lock...
  can't lock file '/var/lock/qemu-server/lock-VM-ID.conf' - got timeout
    

In this case we need to manually delete the lock.

  # rm /var/lock/qemu-server/lock-VM-ID.conf
    

Obviously, this should be a last resort. It's generally not a great practice to forcefully terminate locks, but there are situations where it becomes necessary due to the inability to perform essential tasks.