root@localhost:~# mysql -u root -p
  Enter password:
  ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
  root@localhost:~# service mysqld restart
  Shutting down MySQL..                   [ OK ]
  Starting MySQL.                      [ OK ]
  root@localhost:~# mysql -u root -p
  Enter password:
  ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

 root@localhost:~# find / -name mysql.sock
 /tmp/mysql.sock
 root@localhost:~# mysql -u root -p -S /tmp/mysql.sock
 Enter password:
 Welcome to the MySQL monitor. Commands end with ; or \g.
 Your MySQL connection id is 1
 Server version: 5.6.15-log Source distribution

 Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

 Oracle is a registered trademark of Oracle Corporation and/or its
 affiliates. Other names may be trademarks of their respective
 owners.

 Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

 mysql>

 root@localhost:~# find / -name mysql.sock
 /tmp/mysql.sock
 root@localhost:~# vi /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1

# Disabling symbolic-links is recommended to prevent assorted security risks;
# to do so, uncomment this line:
# symbolic-links=0

# 加上下面的这段代码即可
[mysql]
socket=/tmp/mysql.sock

[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

root@localhost:~# mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.15-log Source distribution

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>