How to change data dir of mysql?

# 1  copy orgin data dir of mysql to new one
 
cp -R /var/lib/mysql /mysqldata
chown mysql:mysql -R /mysqldata
 
# 2 modify configure files, search for datadir in file /etc/mysql/my.cnf
 
#datadir                = /var/lib/mysql
datadir         = /mysqldata
 
# 3 modify configure files, search  in file /etc/apparmor.d/usr.sbin.mysqld
 
#  /var/lib/mysql/ r,
#  /var/lib/mysql/** rwk,
  /bmysqldata/ r,
  /mysql_data/** rwk,
 
# 4 restart your service
 
service mysql restart