Upgrade from 5.x to 6.0 [Part 1]

Proxmox VE 6.x introduces several new major features. Carefully plan the upgrade, make and verify backups before beginning, and test extensively. Depending on the existing configuration, several manual steps—including some downtime—may be required.

Note: A valid and tested backup is always needed before starting the upgrade process. Test the backup beforehand in a test lab setup.

In case the system is customized and/or uses additional packages or any other third party repositories/packages, ensure those packages are also upgraded to and compatible with Debian Buster.

In general, there are two ways to upgrade a Proxmox VE 5.x system to Proxmox VE 6.x:

A new installation on a new hardware (and restoring VMs from the backup)
An in-place upgrade via apt (step-by-step)
In both cases emptying the browser cache and reloading the GUI page is required after the upgrade.