Linux – the equivalent for “service servicename start” that Fedora/RHEL/CentOS uses for Debian/Ubuntu

What is debian-sys-maint used for?

One major thing it is used for is telling the server to roll the logs. It needs at least the reload and shutdown privilege.

See the file /etc/logrotate.d/mysql-server

It is used by the /etc/init.d/mysql script to get the status of the server. It is used to gracefully shutdown/reload the server.

Here is the quote from the README.Debian

* MYSQL WON'T START OR STOP?:
=============================
You may never ever delete the special mysql user "debian-sys-maint". This user
together with the credentials in /etc/mysql/debian.cnf are used by the init
scripts to stop the server as they would require knowledge of the mysql root
users password else.

What is the easiest way to restore it after I've lost it?

The best plan is to simply not lose it. If you really lose the password, reset it, using another account. If you have lost all admin privileges on the mysql server follow the guides to reset the root password, then repair the debian-sys-maint.

You could use a command like this to build a SQL file that you can use later to recreate the account.

mysqldump --complete-insert --extended-insert=0 -u root -p mysql | grep 'debian-sys-maint' > debian_user.sql

Is the password in /etc/mysql/debian.cnf already hashed

The password is not hashed/encrypted when installed, but new versions of mysql now have a way to encrypt the credentials (see: https://serverfault.com/a/750363).

There's nothing that dictates that Fedora is unsuited for use on servers, nor is there anything that dictates that "server distros" is the only choice for servers. It depends on your particular needs.

What you may gain from using the "server distros" is:

• long term support
• stable API's (little to no version-upgrades of libraries and applications)
• backported securityfixes and bugfixes
• paid support

My main "complaint" for the server-distros is that software/libraries tend to to be somewhat old, and the range of supported packages is much smaller than community driven efforts.

I.e. the long term support and the non-changing API's is something that commercial software vendors love, they won't have to rebuild their application for the newest libraries because the API suddenly changed. They can develop for Vendor Y Release X and know that this platform will be around for several years to come.