Backup Fails for Powered-Off Proxmox VMs

Product version: 11.1

Last modified: 29 April 2026

Problem

A backup job fails when processing powered-off virtual machines in a Proxmox VE environment. The job log displays the following error message:

Source host could not create temporary snapshot required to back up the <VM_name> VM

Background

During backup, NAKIVO Backup & Replication creates a temporary snapshot (overlay file) of the VM disk via the Proxmox API.

For powered-off VMs, this operation depends on:

  • Stable Proxmox API connectivity (including Unix socket communication)

  • Sufficient Transporter resources, especially memory

  • Proper permissions to create overlay files on the datastore

If any of these conditions are not met:

  • The snapshot (overlay file) cannot be created

  • The backup job fails at the initial stage

Solution

To resolve the issue, ensure that the Transporter load is reduced, sufficient resources are available, and the Proxmox environment allows snapshot creation.

  1. Reduce the Transporter load. Open the backup job and reduce the number of concurrently processed VMs (for example, set the load to 20 or lower).

  2. Ensure sufficient Transporter resources. Verify that the Transporter has enough available RAM and is not overloaded by multiple running jobs.

  3. Verify permissions for snapshot (overlay) creation. Ensure that the Proxmox host has the required permissions to create temporary overlay files on the datastore used by the VM.