Stefan Bauer writes:
thanks alot. That looks promising. Can we just copy the current mailman3-database and take the configurations or is there a specific migration path we have to follow?
Much of the documentation on mailman.readthedocs.io discusses migrations and upgrades. You should read those for general hints.
The distro Mailman to venv Mailman case is more discussed here on the mailing list than in those documents. I don't have pointers to those threads or the time to look offhand, maybe over the next few weeks as I work on our GSoC project. If you do find any, and would post them here, I'll make sure they get into the docs.
The main thing is to backup Mailman configs (probably in /etc/mailman or /etc/mailman3) and the backend database (core, Postorius, possibly HyperKitty depending on configuration, and the django-mailman auth stuff) before trying to migrate. (For the backend database I would just dump the RDBMS unless non-Mailman content is really huge.) The nature of the virtualenv install is such that it *will not* overwrite any of the distro files at all (as long as you put it in /usr/local or /opt). However, you want to preserve the configs and database and reuse them, so those *must* be backed up.
We are currently running 3.1.1-9 (Ubuntu 18).
Ubuntu 18 is probably old enough that you need to be careful about MySQL and its derivatives. The specific problems are (1) you need to specify the right UTF-8 variant for the coding system, and (2) more recent versions of Mailman tend to make certain records overflow.
If you're using PostgreSQL these caveats *do not* apply. If you're using sqlite3 (I doubt it, but just for completeness) you should change to PostgreSQL or MySQL. If you're using something else (same caveat), I can't really say. Probably somebody out there is using Oracle or whatever, but we don't know about that. :-)
Steve