Change MySQL Data Dir

Stop MySQL Database:

service mysql stop

edit the following in /etc/mysql/my.cnf

datadir         = /srv/mysql

move the existing mysql folder to new location:

mv /var/lib/mysql/ /srv/

if you use an Ubuntu Linux, you have to change all /var/lib/mysql to /srv/mysql /etc/apparmor.d/usr.sbin.mysqld

/srv/mysql/ r,
/srv/mysql/** rwk,

then restart apparmor:

/etc/init.d/apparmor reload

at least start the mysql service again:

service mysql start