Lucky you !
I've been told another solution that is to use the sudo command but the system administrator still have to configure the sudoers file so it's seemingly the same thing for him to install the database himself
Edit : question added
I've achieve to configure rightly the mysql.server script and the my.cnf files and can start and stop a server but there's still the first safe_mysql process who's running (the one it's asked to launch in the mysql documentation)
--> sh ./bin/mysqld_safe --no-default
And I don't know how to stop it. Is it a risk of using the kill command to stop the process ?