This article explains how to change the configuration of the Veeam server so that a backup of virtual machines with HA status "stopped" works.
Error description
During the backup of Proxmox VE VMs with the help of Veeam, the following error message can occur:
"01/09/2025 7:28:08 AM:: hostname-machine : Failed to perform backup: Failed to connect the NBD server to the hypervisor host".
The reason for this is that the virtual machine under Proxmox has the HA status "stopped" and, therefore, the Veeam server cannot reach the virtual machine and cannot back it up.
Solution
Search for the installation directory of your Veeam server and the file "appsettings.json"
hint: The standard path is C:\Program Files\Veeam\Plugins\PVE\Service\appsettings.json
Open the file with administration rights and change the value from <"LockVmOnBackup": false, > to <"LockVmOnBackup": true,>
Restart VeeamPVESvc so that the changes are effective
hint: Check beforehand whether backups or restores are running, if so, wait for them or stop them.
After this, the VM is locked during the backup job and the backup job also runs through with the Ha status "stopped".
More information
If an error occurs during the backup, the VM stays locked after the backup. The VM can be unlocked with "qm unlock <VM-Nummer>".
During the backup, it is possible that Proxmox records some errors, as the VM can not be stopped due to the backup. As the backup will be completed successfully, this error can be ignored. However, it is recommended to fade these notifications in the respective monitoring system.
Niklas Pauli works in the product management team at Thomas-Krenn. He completed his general university entrance qualification at Freyung High School and then his training as an IT specialist for system integration at Thomas-Krenn.AG. After completing his training, he continued to work in the areas of Proxmox VE incl. Ceph, backup (Proxmox, Veeam, SEP). He is also a regular writer for the Thomas-Krenn-Wiki.
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