1、用帐号登录mysql
  mysql –u root
  或#mysql –uroot –p
  2、改变用户数据库
  命令:mysql>use mysql
  mysql> use mysql
  Reading table information for completion of table and column names
  You can turn off this feature to get a quicker startup with -A
  Database changed
  3、修改密码
  密码要用password()函数进行加密!!!!
  命令:mysql> update user set password=password('root') where user='root';
  mysql> update user set password=password('root') where user='root';
  Query OK, 3 rows affected (0.00 sec)
  Rows matched: 3  Changed: 3  Warnings: 0
  4、刷新权限表
  命令:mysql> flush privileges;
  mysql> flush privileges;
  Query OK, 0 rows affected (0.00 sec)
  5、退出mysql并对mysql进行重启即可!!
  service mysqld restart