安装的过程中有这样的一句话：
A RANDOM PASSWORD HAS BEEN SET FOR THE MySQL root USER !
You will find that password in '/root/.mysql_secret'.
You must change that password on your first connect,
no other statement but 'SET PASSWORD' will be accepted.
See the manual for the semantics of the 'password expired' flag.
大概意思就是 一个随机的密码已经生成 可以在 '/root/.mysql_secret'. 中找到
