Comment 12 for bug 448656

Disabling AppArmor may not be desirable solution, but as you see there could be error in apparmor's mysql configuration and then in configuration of mysql itself. When you disable apparmor for debugging you are one step ahead because mysql now actually produces some logs why it can't start (eg in my case some option that just needed to be commented. I doubt that mysqld would run with proper mysql conf and misconfigured apparmor).