Upgrading LXC Container from Debian 12 (Bookworm) to Debian 13 (Trixie)

Prerequisites

• Proxmox VE host with LXC container running Debian 12
• Root access to the container
• Sufficient disk space (at least 10 GB free)
• Container snapshot already taken

Step 1: Snapshot the Container

On the Proxmox host, take a snapshot before proceeding:

pct snapshot <CTID> pre-upgrade-to-b13

Step 2: Update Container Package List

Inside the container:

apt update && apt upgrade -y
apt dist-upgrade -y

Reboot if a new kernel was installed:

reboot

Step 3: Replace Repository Sources

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

Verify the change:

cat /etc/apt/sources.list

Step 4: Clean Up APT Configuration

Remove any Debian 12-specific pinned packages or hold lists:

apt-mark unhold -a
rm -f /etc/apt/preferences.d/*bookworm* /etc/apt/preferences.d/*stretch*

Step 5: Perform the Distribution Upgrade

apt update
apt full-upgrade -y

During the upgrade, you will be prompted about configuration file changes. Review carefully — if unsure, keep the current version.

Step 6: Reboot

reboot

Step 7: Verify the Upgrade

After reboot:

cat /etc/os-release

Expected output should show:

PRETTY_NAME="Debian GNU/Linux 13 (trixie)"
NAME="Debian GNU/Linux"
VERSION_ID="13"
VERSION="13 (trixie)"
VERSION_CODENAME=trixie
ID=debian

Step 8: Post-Upgrade Cleanup

# Remove obsolete packages
apt autoremove -y

# Clean package cache
apt clean

# Check for held packages
dpkg --audit

Troubleshooting

Container fails to boot after upgrade

1. Roll back on the Proxmox host:

   pct undo <CTID>

2. Or restore from snapshot:

   pct undo <CTID> pre-upgrade-to-b13

APT errors about missing packages

apt update --fix-missing
apt install -f

Service failures after upgrade

Check which services are affected:

systemctl list-units --state=failed
journalctl -xe

Resources

• Debian 13 Release Notes
• Proxmox LXC Documentation