Follow https://www.digitalocean.com/community/tutorials/how-to-move-a-mysql-data-directory-to-a-new-location-on-ubuntu-16-04
NOTE: you can skip empty directory (/var/lib/mysql/mysql) creation script in ubuntu 17.xx version.
Then try to start mysql server. If fail then log messages are telling you that /usr/sbin/mysqld needs read (r) access to open /proc/14767/status, /sys/devices/system/node/ (trailing slash because it wants to read the directory), and /proc/14767/task/14767/mem. The file to edit is /etc/apparmor.d/usr.sbin.mysqld.
In my case I solved the problem by adding these lines somewhere in the middle (with two spaces in front of each):
/proc/*/status r, /sys/devices/system/node/ r, /sys/devices/system/node/** r,
Reload apparmor:
sudo apparmor_parser -r /etc/apparmor.d/usr.sbin.mysqld sudo /etc/init.d/apparmor reload
After doing that, try starting MySQL, and if you get more errors, add those files too and try again.
In some case mysql may fail to start for assoc i/o error. So, you may need to disable this settings by adding following line into /etc/mysql/mysql.conf.d/mysqld.cnf
innodb_use_native_aio=0
Another note about file permission of data directory is, “mysql” user should have permission into every directory of that path. Like if new data directory is “/media/myusb01/mysql-data” then “mysql” user should read access of “/media” folder and “/media/myusb01” folder and read write access at new data directory.
Hope mysql will start now.