We believe this installation is heavily modified from the Ubuntu
defaults and that the problem you are experiencing is a result of those
changes. For example, the mysql config file is not /etc/my.cnf, but
/etc/mysql/my.cnf, and so on (there are other changes).
I suggest you revert your changes,
This needs troubleshooting. The mysql logs have a bunch of these:
2018-05-21T01:01:35.759204Z 0 [ERROR] InnoDB: The error means the system cannot
find the path specified.
And dmesg shows many apparmor denied errors:
[ 5343.367505] audit: type=1400 audit(1526864499.821:48): apparmor="DENIED"
