As you can see, mysql exists only in the /etc/init.d
directory and not in /etc/rcN.d
, therefore it shouldn't start on boot.
$ sudo find /etc -regex ".*\(rc.*d\|init\.d\).*" | sudo grep "mysql" | sort
/etc/init.d/mysql
MySQL is started by upstart. You can find the configuration file at /etc/init/mysql.conf