Fix permissions after changing MySQL data directory

• sudo vi /etc/apparmor.d/usr.sbin.mysqld

  /path/to/new_mysql_data_dir/ r,
  /path/to/new_mysql_data_dir/** rwk,

• sudo chown -R mysql:mysql /path/to/new_mysql_data_dir/

• sudo /etc/init.d/apparmor restart
  sudo /etc/init.d/mysql restart