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Upgrading from Proxmox VE 8 to 9

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By Marc Mylemans 2 min read

In this guide, I’ll walk you through how I upgraded my 3-node Proxmox cluster from version 8.4 to 9.0, including the required Ceph upgrade from Reef (18.2.2) to Squid.

This guide is based on the official Proxmox upgrade documentation:

System Overview

  • Proxmox Version: 8.4 (before upgrade)
  • Ceph Version: Reef (18.2.2)
  • Cluster Nodes: 3
  • Storage: Ceph cluster

Step 1: (Optional) Upgrade Ceph from Reef to Squid

If you’re running a Ceph cluster, it’s important to upgrade Ceph before upgrading Proxmox to ensure compatibility.

We’ve written a detailed guide specifically for this process:
How to upgrade Ceph from Reef to Squid

If you’re not using Ceph, or just running a single-node setup without distributed storage, you can skip this step.

Important: If you do use Ceph, always verify cluster health with ceph status before proceeding.

Step 2: Upgrade All Proxmox Packages

On each node, update all packages to the latest version of Proxmox 8:

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apt update && apt full-upgrade

Reboot the node if any kernel or low-level upgrades were applied.

Step 3: Run the pve8to9 Check Tool

Run the official upgrade checker:

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pve8to9

This tool scans your node for potential problems or unsupported configurations. Resolve any critical issues before proceeding.

Step 4: Update APT Sources to Trixie

Use sed to bulk-replace bookworm with trixie in all relevant APT source files:

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sed -i 's/bookworm/trixie/g' /etc/apt/sources.list 
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/*.list

If you’re using custom repositories (like No-Subscription or Ceph), update those accordingly.

Tip: Check that pve-enterprise.list or pve-no-subscription.list also point to trixie.

Step 5: Update and Dist-Upgrade

Now refresh your APT cache and start the full distribution upgrade:

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apt update
apt dist-upgrade

During the upgrade, you might be prompted about keeping or replacing configuration files. I selected the default option in all cases to avoid overwriting anything critical.

Your experience may vary — if you’ve heavily customized Proxmox configs, review diffs before confirming.

Step 6: Reboot the Node

Once the upgrade completes, reboot the node:

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reboot

Verify everything is working properly once it comes back up:

  • pveversion
  • systemctl status pvedaemon
  • ceph status

Repeat for all other nodes in the cluster.

Final Check

After upgrading all nodes:

  • Verify Ceph cluster is healthy
  • Check all VMs and containers are running
  • Confirm HA resources (if used) are behaving as expected

Lessons Learned

  • The pve8to9 tool is extremely helpful — don’t skip it!
  • Make sure Ceph is upgraded before touching Proxmox.
  • Doing one node at a time makes rollback easier in case of problems.
  • Selecting the default config file options worked fine for me, but back up /etc just in case.

Bonus: Quick Commands Recap

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# Step-by-step upgrade commands
apt update && apt full-upgrade
pve8to9

sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/*.list

apt update
apt dist-upgrade
reboot

Got Questions?

Feel free to drop a comment on my YouTube channel or reach out on Bluesky!

Happy upgrading and may your cluster run smooth!

Proxmox, Upgrade 8 to 9
Proxmox Homelab Ceph Upgrade Cluster
This post is licensed under CC BY 4.0 by the author.