Note to self, when moving the path where mysql stores it’s files, make sure you edit the App Armour file to allow mysqld to write to the new location.

Time wasted: 30 minutes.

The message:

kernel: [422118.789696] audit(1233167081.635:38): type=1503 operation="inode_create"
requested_mask="w::" denied_mask="w::" name="/opt/mysql/pluto.lower-test"
pid=12412 profile="/usr/sbin/mysqld" namespace="default"

The solution: edit this file;

/etc/apparmor.d/usr.sbin.mysqld

And add the necessary new paths… Good times, right there.