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

I have not started mysql for quite a long time , then some mistake taken when I start: mysql -uroot -p

There's no such file "/var/lib/mysql/mysql.sock" , not event  in my  whole disk .

I tried: 

[dengwei@localhost repos1]$ sudo /etc/rc.d/init.d/mysqld start
[sudo] password for dengwei:
MySQL Daemon failed to start.
Starting mysqld: [FAILED]

after search on web, I tried:

[dengwei@localhost ~]$ sudo /usr/bin/mysqld_safe
[sudo] password for dengwei:
130125 16:34:29 mysqld_safe Logging to '/var/log/mysqld.log'.
130125 16:34:29 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
130125 16:37:45 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

 now there is /tmp/mysql.sock

 ln -s /tmp/mysql.sock /var/lib/mysql/mysql.sock

now we can run mysql via: $mysql

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