journalctl -u mysql.service -f

mysqld[]: mysqld: Can’t read dir of ‘/etc/mysql/mysql.conf.d/’ (Errcode: 13 – Permission denied)
mysqld[]: mysqld: [ERROR] Fatal error in defaults handling. Program aborted!
mysql.service: Control process exited, code=exited, status=1/FAILURE
systemd[1]: mysql.service: Failed with result ‘exit-code’.
systemd[1]: Failed to start MySQL Cluster Community Server.

ln -s /etc/apparmor.d/usr.sbin.mysqld /etc/apparmor.d/disable/
apparmor_parser -R /etc/apparmor.d/usr.sbin.mysqld