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

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

probable solution for linux :
1. sudo /etc/init.d/mysqld start
2. mysql -u username -p
(then password)