root密码修改：
mysql> use mysql;
mysql> UPDATE user SET Password = PASSWORD('newpass') WHERE user = 'root';
mysql> FLUSH PRIVILEGES;
问题：Access denied for user 'root'@'192.168.46.161' to database 'db3'
mysql> grant all on db3.* to 'root'@'%' identified by '123456' with grant option;
musql> FLUSH PRIVILEGES;;