本方法在路由上测试，其他系统应该一样

[RT-N14U /home/root]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.1.73 Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

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
mysql> select host,user from user;
+-----------+------+
| host      | user |
+-----------+------+
| 127.0.0.1 | root |
| localhost |      |
| localhost | root |
| rt-n14u   |      |
| rt-n14u   | root |
+-----------+------+
5 rows in set (0.00 sec)

mysql> update user set host = '%' where user = 'root';
ERROR 1062 (23000): Duplicate entry '%-root' for key 'PRIMARY'
mysql> select host,user from user;
+-----------+------+
| host      | user |
+-----------+------+
| %         | root |
| 127.0.0.1 | root |
| localhost |      |
| rt-n14u   |      |
| rt-n14u   | root |
+-----------+------+
5 rows in set (0.00 sec)

mysql> grant all privileges on *.* to 'root'@'%' identfied by 'admin' with grant optioERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresith grant option' at line 1
mysql>
mysql>
mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY 'admin' WITH GRANT OPTI
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> exit
Bye
[RT-N14U /home/root]# mysql -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
[RT-N14U /home/root]# mysql -u -p
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.1.73 Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> exit
Bye
[RT-N14U /home/root]#