Upgrading Debian 11 ("Bullseye") to Debian 12 ("Bookworm")

Category: Debian
Created: 2023-05-04

Upgrading a Debian installation to the next major version number works quite smoothly. Depending on the speed of the server and the duration of the reboot, an upgrade is usually completed in under 15 minutes.

Always upgrade Debian Linux from one version to the next higher, do not skip versions!

To upgrade a server from Debian 10 to Debian 12, you must first upgrade from 10 to 11 and then from 11 to 12. Reboot the server after each upgrade!

Follow the steps below to upgrade:

update /etc/apt/sources.list (replace bullseye with bookworm)
if necessary, update the file /etc/apt/sources.list.d/liveconfig.list for the LiveConfig PHP repository in the same way
run apt update
run apt upgrade
run apt full-upgrade. While running, you will be asked whether some existing configuration files should be replaced - in most cases it is better to keep the existing configuration (answer with no).
run apt-get autoremove to remove all packages that are no longer required
reboot the server (that’s important to switch the kernel and all kernel modules)
then log in to LiveConfig as admin and go to Server Management → E-Mail. Save the configuration for Postfix and for Dovecot again (this will update the configuration files and adapt them for Debian Bookworm).

You can also find detailed information on upgrading from Debian 10 in the official documentation.

Possible problems

in the BIND configuration file /etc/bin/named.conf.options, the setting dnssec-enable = yes; needs to be removed. If you update the BIND configuration via LiveConfig, this happens automatically.

Currently we’re not aware of any more problems. If you have any issues, please let us know so we can update this article accordingly.

New in Debian 12

Some things have changed with Debian Bookworm (see Release Notes). Some important changes are:

DNSSEC is now enabled by default and can’t be disabled
the service spamassassin has been renamed to spamd