Upgrading Proxmox 8 to 9

So I finally managed to find some time to upgrade my proxmox hypervisor from version 8 to version 9. Thought this would be much of a fuss, but it really wasn't. All in all it took me ~30 minutes.

I followed the official proxmox guide very closely.

This serves mainly as documentation for myself.

Preparations

• Run pve8to9 to make sure all preconditions are met. The I did the following adjustments:
  • Remove systemd-boot as it should not be needed and I did not explicitly install it
• Check /etc/apt/sources.list

root@pve:~# cat /etc/apt/sources.list
    deb http://ftp.de.debian.org/debian bookworm main contrib non-free-firmware
    deb http://ftp.de.debian.org/debian bookworm-updates main contrib non-free-firmware
    
    # security updates
    deb http://security.debian.org bookworm-security main contrib non-free-firmware
    
    deb http://download.proxmox.com/debian/pve bookworm pve-no-subscription

• Add non-free-firmware component to debian repos and install `intel-microcode`
• update sources with `sed -i 's/bookworm/trixie/g' to all files under `/etc/apt/`
• apt update and apt policy to verify new sources
• stop all VMs (have backups before!)

Performing the upgrade

• apt dist-upgrade during which I did the following selections:
  • Install package maintainers file for:
    • /etc/chrony/chrony.conf
    • /etc/lvm/lvm.conf
  • Keep my version for:
    • /etc/apt/sources.list.d/pve-enterprise.sources
• After that I ran pve8to9 again, then did a reboot

After upgrading

• apt modernize-sources to update all my debian sources to the new deb822 format