Upgrading Proxmox Like a Boss (a.k.a. “Don’t Panic”)

So, Debian 13 dropped last weekend, and of course I couldn’t resist the urge to update my Proxmox server.
Since Proxmox is basically Debian wearing a fancy virtualization cape, it also moved from the 8.x series to the glorious 9.x.

Yesterday, I pulled the trigger on the upgrade — and surprisingly, the universe didn’t implode.
But here’s the play-by-play for anyone who wants to follow in my dangerously curious footsteps.

Step 0: Check yourself before you wreck yourself

First, I made sure everything was already up-to-date in the installed version.
There’s a built-in script called pve8to9 which acts like your personal “Upgrade Oracle” and warns about potential system landmines.
In my case, the systemd-boot meta-package was installed, and the Proxmox upgrade tool recommended removing it to avoid bootloader-related package conflicts during the upgrade.

apt remove systemd-boot

Yes, I know… removing something sounds counterintuitive when you’re preparing for an upgrade, but hey — that’s Linux life.

Step 1: Summon the Oracle

pve8to9 --full

Step 2: Switch your Debian base to “Trixie” (because “Bookworm” is sooo last season)

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

Step 3: Add the No-Subscription Repo (because… budgets)

cat > /etc/apt/sources.list.d/proxmox.sources << EOF
Types: deb
URIs: http://download.proxmox.com/debian/pve
Suites: trixie
Components: pve-no-subscription
Signed-By: /usr/share/keyrings/proxmox-archive-keyring.gpg
EOF

Step 4: The Moment of Truth

apt update
apt dist-upgrade

Step 5: One last prophecy check and the big red button

pve8to9 --full
reboot

Important note:

During the whole ritual, all VMs were shut down and fully backed up using Proxmox’s built-in backup feature.
Better safe than explaining to your boss why production is gone forever. 😅

Results

Everything went smooth — no errors, no weirdness. My Proxmox is now running happily on Debian 13.

My desktop PC, however… let’s just say it went full drama mode.
Apparently, NVIDIA drivers decided to throw a tantrum during the upgrade.
At the moment, the machine is in a Schrödinger’s-PC state — both broken and fixable, depending on my patience level.

Stay tuned for Part 2: “How I Tamed the NVIDIA Beast.”

Disclaimer: If you brick your server by following this, that’s on you.
If it works flawlessly, I’ll happily take all the credit.