Proxmox 8 to 9 upgrade

As the Proxmox 8 EOL was coming up fast (2026-08-31), I needed to do the upgrade.

Prepare for Upgrade

 Ran pve8to9 and then pve8to9 --full

• suggested to install intel-microcode
• added non-free and non-free-firmware to /etc/apt/sources.list
• apt update
• apt install intel-microcode

Ensured Proxmox 8 was up to date

• apt update
• apt dist-upgrade
• pveversion

Perform the Upgrade

Replace bookworm with trixie

• sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
• Add a proxmox.sources:

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

• Remove outdated Proxmox source (may not exist on your system)
• rm /etc/apt/sources.list.d/pve-install-repo.list

Ensure the apt sources changes worked

• apt update

Perform the upgrade (recommend doing ti from ssh shell and not Proxmox web shell)

• apt dist-upgrade

Reboot

• shutdown -r now

After install cleanup

Comment out the Enterprise source and test it:

• /etc/apt/sources.list.d/pve-enterprise.sources
• apt update

Migrate to the new .sources format:

• apt modernize-sources
• apt update

Appendix

Sources

• https://pve.proxmox.com/wiki/Upgrade_from_8_to_9
• https://forum.proxmox.com/threads/what-is-correct-way-to-install-intel-microcode.75664/