Proxmox 8 to 9 Upgrade: A Practical Guide

If your Proxmox VE 8 screen is warning that support has ended, this is the practical route I used to move my Home Assistant host to Proxmox VE 9.

Before you touch anything: back it up. Create a Home Assistant backup, download it somewhere away from the Proxmox box, and back up any other VMs or containers. A Proxmox snapshot is useful, but it is not the same thing as having a backup somewhere safe.

1. Check what you are running

Open your Proxmox host, go to Shell and check the PVE version. If you are already on version 9, stop here. If you are on 8, make sure version 8 is completely up to date before attempting the major upgrade.

2. Update Proxmox 8 first

Refresh the package lists and perform a full upgrade. If packages were updated, reboot before continuing. You want the cleanest possible starting point.

3. Run the Proxmox 8-to-9 checker

Run the pve8to9 checker before upgrading. Fix the warnings and failures it reports rather than blindly carrying on. In my installation I had to deal with the systemd-boot package and install the appropriate Intel microcode. Your results may be different, especially if you use AMD hardware or have a more complicated Proxmox setup.

4. Change the Debian and Proxmox repositories

Proxmox VE 8 is based on Debian Bookworm; Proxmox VE 9 moves to Debian Trixie. Update the Debian and Proxmox repository definitions carefully. If you need non-free firmware, make sure the repository configuration includes it.

5. Check again

Run pve8to9 again. Do not treat warnings as decorative. Read them and resolve anything relevant to your machine before starting the main upgrade.

6. Perform the full upgrade

Refresh the package lists again and run the full distribution upgrade. Read the prompts rather than repeatedly pressing Enter. If you have manually modified a configuration file, think before replacing it with the package maintainer version.

7. Reboot and verify

If the upgrade completes without errors, reboot. Confirm the Proxmox interface reports version 9, then start Home Assistant and your other guests. Check networking, backups and any USB passthrough devices such as Zigbee coordinators.

If it goes wrong

Do not reboot blindly after serious package errors. Record the error and investigate it first. This is also why the backups at the beginning matter: worst case, you can install Proxmox 9 cleanly, recreate Home Assistant and restore your Home Assistant backup.

Watch the walkthrough

Tech without the technobabble — and with the mistakes left in so you can see what actually happens.