mysql服务启动，但是连接不上，如何解决？

登陆报错：

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)

分析原因：

原因不详，知道了补上

解决方案一：

root@lo..