Upgrade Proxmox Backup Server 3 to 4 — Step-by-Step Guide (PBS 3.4 → 4.0)

Upgrade Proxmox Backup Server 3 to 4 — Step-by-Step Guide

This guide walks you through upgrading Proxmox Backup Server (PBS) from version 3.4 to 4.0, including the transition from Debian 12 (Bookworm) to Debian 13 (Trixie). Follow each step carefully to ensure a safe and successful upgrade.

Prerequisites

Running PBS 3.4.2-1 or newer
Full backup of PBS configuration
At least 10 GB free on root filesystem
Access to physical console or IPMI
Console access in case of network changes

1. Check current PBS version

proxmox-backup-manager versions

2. Backup your configuration

tar czf "pbs3-etc-backup-$(date -I).tar.gz" -C /etc proxmox-backup

3. Run the pre-upgrade checklist

pbs3to4 --full

Re-run after fixing any reported issues.

4. Optional: Set datastores to read-only

proxmox-backup-manager datastore update DATASTORE-ID --maintenance-mode read-only

5. Update PBS 3.4 to latest

apt update
apt dist-upgrade
proxmox-backup-manager versions

6. Install Proxmox archive keyring for Trixie

wget https://enterprise.proxmox.com/debian/proxmox-archive-keyring-trixie.gpg \
  -O /usr/share/keyrings/proxmox-archive-keyring.gpg

7. Switch Debian repos from Bookworm to Trixie

sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/*.list || true
grep -R "bookworm" /etc/apt/sources.list* || true

8. Add PBS 4 repositories

Enterprise repo:

cat > /etc/apt/sources.list.d/pbs-enterprise.sources <<EOF
Types: deb
URIs: https://enterprise.proxmox.com/debian/pbs
Suites: trixie
Components: pbs-enterprise
Signed-By: /usr/share/keyrings/proxmox-archive-keyring.gpg
EOF

No-subscription repo:

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

9. Upgrade the system

apt update
apt dist-upgrade

10. Reboot

systemctl reboot

11. Post-upgrade checks

Reload PBS web UI (clear browser cache)
Check services:

systemctl status proxmox-backup.service proxmox-backup-proxy.service

Re-run upgrade checker:

pbs3to4 --full

Remove read-only mode:

proxmox-backup-manager datastore update DATASTORE-ID --delete maintenance-mode

📺 Video Tutorial

Watch the complete upgrade process in video form:

Proxmox Backup Server 3 to 4 Upgrade Video