8

Great (you did say you created the file :))

When you restarted the service did you get a warning?

You are basically starting the service as it was before, it doesn’t yet know to include the override. If you do a systemctl status mariadb.service it will tell you if you are using the override file.

Try that command then

sudo systemctl daemon-reload

Then the status again. I expect it will list the override file then (and it may start!).

[edit]
You should see something like this

  Drop-In: /etc/systemd/system/mariadb.service.d
           └─override.conf