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Introduction

Proxmox is a powerful virtualization platform, but occasionally you may encounter issues where a VM becomes locked due to a backup process. This can prevent users from rebooting or making any changes to the VM, resulting in the error message “VM is locked (backup) (500)”. This guide will walk you through the steps to unlock both KVM and LXC VMs, allowing you to regain control and resume normal operations.

Understanding the Error

The error “VM is locked (backup) (500)” typically occurs when:

• A backup process is currently running or has gotten stuck.
• A manual Proxmox backup process was interrupted or failed.
• Proxmox automatically locks the VM during a backup to ensure data consistency.

When a VM is locked, you won’t be able to perform operations like rebooting, shutting down, or making configuration changes until the lock is removed

In order to solve this issue, simply run this command in the proxmox SSH.

To unlock KVM VM

qm unlock <VM ID>

Replace <VM ID> with the actual ID of the VM you wish to unlock. For example, if your VM ID is 101, the command would be:

qm unlock 101

If the VM is an LXC container, use the pct unlock command followed by the VM ID. This command removes the lock from the specified LXC container.

pct unlock <VM ID>

Replace <VM ID> with the actual ID of the LXC container you wish to unlock. For example, if your LXC container ID is 102, the command would be:

pct unlock <VM ID>

Conclusion

Encountering the “VM is locked (backup) (500)” error in Proxmox can be frustrating, but it is relatively easy to resolve. By following the steps outlined in this guide, you can unlock both KVM and LXC VMs and resume normal operations. Always ensure to properly monitor and manage backup processes to minimize such issues. If you continue to experience problems, consider reaching out to Proxmox support or consulting the Proxmox documentation for further assistance.