Systemd Mysql won't stop

I had the same problem (upgrade to 15.04, using official files and config).

I had to make the following changes to be able to stop the mysql daemon manually with sytemctl and automatically on system reboot/shutdown:

1. Make /etc/mysql/debian.cnf readable for the mysql user with

   sudo chgrp mysql /etc/mysql/debian.cnf; sudo chmod 640 /etc/mysql/debian.cnf
   

2. Provide a slightly modified mysql.service file:

   sudo cp /lib/systemd/system/mysql.service /etc/systemd/system/
   sudo chmod 755 /etc/systemd/system/mysql.service
   

3. Provide an explicit stop command by opening the copied file in an editor:

   sudo nano /etc/systemd/system/mysql.service
   

   and adding the following line under the [Service] section:

   ExecStop=/usr/bin/mysqladmin --defaults-file=/etc/mysql/debian.cnf shutdown
   

   In Nano, use Ctrl+O to save (Linux way!), Ctrl+X to exit.

4. Make the new service file known to system:

   sudo systemctl daemon-reload