尝试查询mysql状态时出错

Question

我正在尝试查看mysql是否正在运行。当我这样做时：

 mysqladmin -u root -p status

我明白了：

connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)'
Check that mysqld is running and that the socket: '/tmp/mysql.sock' exists! 

但是当我这样做时：ps aux | grep mysql我得到了一个合适的PID和运行它的用户。

为什么在第一种情况下会出错？