Is There Already a Safe Upgrade Guide from Debian 12 to Debian 13?

Has anyone already tested a reliable and secure migration process from Debian 12 (Bookworm) to Debian 13 (Trixie)?

 

After upgrading a server with ISPConfig from Debian 12 (Bookworm) to Debian 13 (Trixie), Apache failed to start with this error:

Cannot load /usr/lib/apache2/modules/mod_python.so
The issue was caused by an old mod_python configuration left enabled after the upgrade, even though the module is no longer available/supported.
No websites or ISPConfig services were using mod_python.
Fix:

sudo a2dismod python
sudo apachectl configtest
sudo systemctl restart apache2

After disabling the obsolete module, Apache and ISPConfig worked normally again.

 

We ran into similar issues migrating 9 production sites from a bare LAMP stack to ISPConfig on a fresh Debian 13 VPS (rather than upgrading in-place). The mod_python issue you describe is a good example of why we chose a clean install over an upgrade path.

We open sourced the scripts we used, including pre-flight checks, ISPConfig API-based site creation with retry logic, PHP version assignment per site, and CSF setup. You can find it by searching GitHub for hydtie/ispconfig-migrate.

One thing worth adding to your mod_python fix: before restarting Apache, run apache2ctl -M to check for any other deprecated modules that survived the Debian 12-to-13 upgrade. We found a few surprises that way.