Proxmox VE (Virtual Environment) continues to evolve as one of the most popular open-source virtualization platforms, combining KVM virtualization and LXC containers with built-in clustering, storage integration, and backup tools. With the release of Proxmox VE 9, administrators running Proxmox VE 8 will want to plan their upgrades carefully.

This article provides a step-by-step guide to upgrading from Proxmox VE 8 to Proxmox VE 9, covering preparation, repository configuration, the upgrade process, and best practices.

Why Upgrade to Proxmox VE 9?

Upgrading ensures your virtualization environment remains:

• Secure – Access to the latest Linux kernel, QEMU, and Proxmox bug/security patches.
• Feature-Rich – New cluster management features, storage backends, and performance enhancements.
• Compatible – Full support for newer guest operating systems and hardware.
• Future-Proof – Proxmox typically supports a release for many years, so staying current avoids future “big bang” upgrades.

Preparation Before Upgrading

A successful upgrade begins with careful planning.

1. Backup Everything

• Use Proxmox Backup Server or vzdump to create backups of all VMs and containers.
• Backup important system configs:

  cp -a /etc/pve /root/etc-pve-backup
  cp -a /etc/network/interfaces /root/interfaces-backup
  

2. Check Cluster Health (if applicable)

On each node, run:

pvecm status

Make sure quorum is healthy and all nodes are in sync.

3. Check Installed Versions

pveversion -v

Confirm that all nodes in the cluster are running Proxmox VE 8.x and fully updated.

4. Update to the Latest PVE 8 Release

apt update
apt dist-upgrade -y
reboot

Adjusting the Repositories

Proxmox VE is based on Debian. Proxmox VE 8 runs on Debian 12 “Bookworm”, while Proxmox VE 9 will run on Debian 13 “Trixie”.

You need to update the repository configuration files:

Step 1: Edit APT Sources

• Open /etc/apt/sources.list and change bookworm → trixie.
• Update Proxmox repo in /etc/apt/sources.list.d/pve-no-subscription.list (or enterprise list).

For non-subscription repo:

deb http://download.proxmox.com/debian/pve trixie pve-no-subscription

Step 2: Update Ceph Repository (if using Ceph)

If you run Proxmox with Ceph, adjust:

/etc/apt/sources.list.d/ceph.list

Replace with the Ceph release supported by PVE 9 (e.g., Ceph Reef → Ceph Squid).

Performing the Upgrade

Now you are ready for the upgrade process.

1. Update Package Lists

   apt update
   

2. Simulate the Upgrade

   apt dist-upgrade --dry-run
   

   This shows what will be changed without making modifications.

3. Run the Full Upgrade

   apt dist-upgrade
   

   This step will take time depending on the number of packages.

4. Reboot the Node

   reboot
   

5. Check the Version
   After reboot:

   pveversion
   

   You should see pve-manager/9.x confirming the upgrade.

Cluster Upgrade Strategy

If you are running a multi-node Proxmox VE cluster:

• Upgrade one node at a time.
• Migrate workloads off the node before upgrading (live migrate VMs/containers).
• Verify the upgraded node before proceeding to the next.
• Ensure Ceph (if in use) remains healthy after each upgrade.

Post-Upgrade Checklist

After completing the upgrade:

1. Check Cluster Status

   pvecm status
   

2. Verify Storage
   Confirm that ZFS, LVM, NFS, or Ceph storage is functioning as expected.
3. Update Guest Tools
   Update qemu-guest-agent inside your VMs for full compatibility.
4. Monitor Logs

   journalctl -xe
   

   Look for errors or warnings.

Best Practices for a Smooth Upgrade

• Schedule Downtime: Even though live migration helps, kernel updates require reboots.
• Test First: If possible, test the upgrade on a lab node before applying it to production.
• Use tmux or screen: Prevents issues if SSH disconnects mid-upgrade.
• Follow Proxmox Release Notes: Each release may have specific steps or known issues.

Conclusion

Upgrading from Proxmox VE 8 to Proxmox VE 9 is a straightforward process if you prepare properly. With backups, correct repositories, and a careful node-by-node approach in clusters, you can enjoy the new features, stability improvements, and security updates Proxmox VE 9 brings.

By staying current with Proxmox’s release cycle, you ensure your virtualization environment remains reliable, scalable, and ready for modern workloads.