Proxmox Backup Warns about SQL Log Truncation Permissions

Product version: 11.1

Last modified: 26 January 2026

Problem

When running a backup of a Proxmox VM with SQL log truncation enabled and QEMU Guest Agent installed and running, the SQL log truncation fails with the following permission error:

The "SQL Server Log Truncation" action was partially executed for the "SSQL-02" VM.

The action could not be executed in the full scope. Reason: Provided user account has no permission to process the database.

The error occurs even though the backup itself starts normally.

Background

If the QEMU Guest Agent service runs under the Local System account, it may not have sufficient permissions to truncate SQL transaction logs. As a result, the log truncation step fails, even though the guest agent itself is installed and running.

Solution

To solve the issue, configure the QEMU Guest Agent service to run under an Administrator account on the guest VM:

  1. Log in to the guest OS (Windows) of the affected Proxmox virtual machine and open Services.

  2. Locate the QEMU Guest Agent service and open the Properties > Log On tab.

  3. Change the service account from Local System to Administrator.

  4. Apply the changes and restart the QEMU Guest Agent service.

  5. Rerun the backup job.

After switching the service to run under the Administrator account, SQL log truncation completes successfully, and the backup job finishes without errors.