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).
As womble said, grab the OMSA packages from that blog post and use NRPE to call check_openmanage.
This'll give you good coverage over all the Dell hardware in your box (including the RAID array(s))
Best Answer
speaking from perspective of poweredge user running mostly debians:
do you really want to run this heavy management thing on each and every server you have?
truth is you don't really need most of those fancy tools. you do need raid monitoring - but that one you can usually get as binary package from actual raid vendor [ lsi in most cases for dell/ibm/hp ]. you might want to monitor via ipmi general health status - but this will be vendor independent as long as ipmi functionality is provided by motherboard/addon management card.
and omsa for dell is available for debian too: here.