It seems there are three passwords necessary to initialize a Mediawiki/Semanticmediawiki
- The MySQL root password
- The MySQL wiki user password
- The MediaWiki Sysop password
Fully automatic installations may need to create random passwords for all three of these. Some users might be more happy interactively editing the passwords.
The Digital Ocean environment used to have a MediaWiki "One-Click" app in the past. It would show the Passwords in the motd message when you logged in to the container.
The ProfiWiki Installation has used files like /root/.sysop.password in the past to store passwords. From a safety point of view these two choices are not optimal. Docker swarm supports https://docs.docker.com/engine/swarm/secrets/ which I did not try out yet and that seems to ask for another layer of infrastructure. What solution would you think is best?