with MySQL on another drive

#Stopping the Default Install/Instance
service mysqld stop

#Clear Current Config
rm /etc/my.cnf

#Uninstal the Default Install/Instance
yum remove mysql mysql-server -y

#Clear Current Datadir
test -d /var/lib/mysql/ && rm -rf /var/lib/mysql/

#Clear the 'New' Datadir
test -d /mysql/mysql/ && rm -rf /mysql/mysql/

#Install it again
yum install mysql mysql-server -y

#Check the service status
service mysqld status

#Start it - just to create a first/default structure
service mysqld start

#Check the service status
service mysqld status

#Interrupt the current MySQL server installation
service mysqld stop

#Ensure that you don´t have anymore instance/service running
ps axu | grep mysql

#Move the mysql data directory to '/mysql' partition and create the symbolic link
test -d /var/lib/mysql/ && mv /var/lib/mysql/ /mysql/ && ln -s /mysql/mysql /var/lib/

#Check symbolic link and the real path
ls -lrth /var/lib/ | grep mysql 

#Set permission on new Datadir
chown -R mysql:mysql /mysql/mysql

#Start it
service mysqld start

#Try to connect (keep in mind that the default install of MySQL doesn´t set a 'pwd' for 'root' user and then you should connect with 'blank password'
mysql -u root -p --host 127.0.0.1

#Once connected to MySQL, create a new db just to test if it´s working and where MySQL will create folder/file structure
create database DBTesteNew;
exit

#Check if the new db is on the 'new datadir'
ls /mysql/mysql

#Make sure the mysqld is set to start on boot time 
chkconfig mysqld on

#restart

reboot

from：https://www.centos.org/forums/viewtopic.php?t=6732