The error when I try to start MySQL server in the VPS.
Another MySQL daemon already running with the same unix socket
I googled it and found the solution.
Since I am working on CentOS, enter the following command in console
service mysqld stop
mv /var/lib/mysql/mysql.sock /var/lib/mysql/mysql.sock.bak
service mysqld start
I think the problem is due to hard power off. The server is not shutdown properly. So the mysql.sock is not deleted on rebooting.