mysql 配置文件目录：/etc/my.cnf
root 密码为空的时候配置文件中下面这句：
skip-grant-tables
GRANT ALL PRIVILEGES ON *.* TO IDENTIFIED BY '123' WITH GRANT OPTION;
执行这句时候错误：
ERROR 1290 (HY000): The MySQL server is running with the --skip-grant-tables option so it cannot execute this statement这个时候我们只需要
flush privileges
一下，在添加用户就OK了，
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)
mysql> GRANT ALL PRIVILEGES ON . TO IDENTIFIED BY '123' WITH GRANT OPTION;
Query OK, 0 rows affected (0.00 sec)
这个时候我们成功搞定了，再登录就可以了。
如果报错如下信息：
Error: Cannot retrieve repository metadata (repomd.xml) for repository: InstallMedia. Please verify its path and try again
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
我们只要到/etc/yum.repo.s下面把packetxxxx.repo和redhat.repo两个文件删除掉，再启动就可以了，
