I installed Mattermost Debian package on my Ubuntu server with MySQL.
I know Omnibus supports PostgreSQL. I wonder how to migrate from MySQL to PostgreSQL.
What are the procedures if I want to migrate from debian package to Omnibus installation?
There’s no official migration path from MySQL to PostgreSQL unfortunately at the moment. Check out this GitHub issue for a lenghty discussion about how this could be achieved, YMMV:
Your debian package also probably does not have the configuration in the database, Omnibus does - so after installing the Omnibus setup, you would have to transfer your MySQL data to the PostgreSQL instance on the Omnibus installation and once that’s done, you should be able to start the server with an empty configuration file (because there is none in the database).
Use the command mmctl --local config edit afterwards to paste the configuration from your Debian setup in, save it and restart the server.