ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

Today my MYSQL is not working.

When i try to connect mysql server, as follows:

mysql -u root -p

I get the error:
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

this because my database server is not started, start it using:

//centos 7 server

systemctl start mysqld

//centos 6 server

service mysqld start