Installing PostgreSQL is trivially easy.
You just have to use the same name for linux user, database user and the database name.
It still works in 2023 with Debian 11-Bullseye, I just added 'systemctl' command to start the daemon. Very old systems start the daemon automatically, so they don't need 'systemctl' command.
$ sudo apt-get update
$ sudo apt-get -y install postgresql $ sudo systemctl start postgresql $ sudo -u postgres createdb tero $ sudo -u postgres createuser tero
Use your own login name instead of “tero”.
$ psql
Yes, that’s all. You can now start writing SQL.