Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock'

/usr/bin/mysqladmin: connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
Check that mysqld is running and that the socket: '/var/run/mysqld/mysqld.sock' exists
先查看/var/log/mysql.err
发现为空，说明mysql没有起来。
再查 daemon.log
也只提示mysqld错误，
查看syslog 发现如下信息
/usr/sbin/mysqld: Disk is full writing '/var/log/mysql/mysql-bin.000442' (Errcode: 28). Waiting for someone to free space
原来是硬盘空间不足了！
呵呵，mv走一部分log。mysql自动起来了！
类似问题可能也有以下原因
1，目录没有写权限
2，ip地址更换后与/etc/mysql/my.cnf中bind address不一致.修改ip bind. 然后/etc/init.d/mysql restart 应该可以搞定.