How to Upgrade to Debian 12

Author: Leo Nguyen Jun 12, 2023

This post will show you how to upgrade Debian 11 (Bullseye) to Debian 12 (Bookworm).

Step 1: Create backup

This is very important. If something goes wrong, you can always go back from the backup/snapshot.

Step 2: Update current packages

sudo apt update
sudo apt upgrade
sudo apt full-upgrade
sudo apt autoremove

Step 3: Upgrade to the new version of Debian

cat /etc/apt/sources.list # inspect content
sudo sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list

cat /etc/apt/sources.list.d/*.list # inspect content
sudo sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list.d/*.list

sudo apt update
sudo apt upgrade
sudo apt full-upgrade
sudo apt autoremove

Tips:

  1. During the upgrade process, Debian may ask you to handle a modified config file. It's generally a good idea to install the package maintainer's version (unless you have a reason not to), then set your custom settings in a separate config file.

  2. The full-upgrade part may install further packages that were held back during the normal upgrade part. Database servers (like MariaDB) are one example.

Step 4: Configure new system

Configure your new system accordingly, such as pointing the nginx sites to the correct updated php-fpm version.

Step 5: Reboot

A reboot is recommended to fully update your operating system and ensure a complete restart of system and services.

sudo reboot