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mysql免密码登录下无法创建用户（分析mysql创建用户的方法）

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一、用户与权限管理

（一）grant

1、help grant

和权限相关的命令关键字grant可通过help查看其用法：

mysql> help grant;
Name: 'GRANT'
Description:
Syntax:
GRANT
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    TO user_specification [, user_specification] ...
    [REQUIRE {NONE | ssl_option [[AND] ssl_option] ...}]
    [WITH with_option ...]

...
CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass';
GRANT ALL ON db1.* TO 'jeffrey'@'localhost';
GRANT SELECT ON db2.invoice TO 'jeffrey'@'localhost';
GRANT USAGE ON *.* TO 'jeffrey'@'localhost' WITH MAX_QUERIES_PER_HOUR 90;
...

2、grant授权

对于上述：

GRANT ALL ON db1.* TO 'jeffrey'@'localhost';

它实际包含了两条命令，先是创建用户jeffrey，然后才是对这个用户进行授权。如下：

mysql> create user 'jeffrey'@'localhost' identified by 'mypass';
mysql> grant all on db1.* to 'jeffrey'@'localhost' identified by 'mypass';

对于授权语句的一些关键字解释如下：

grantall privilegeson dbname.*to username@localhostIdentified by ‘mypass’
授权命令对应权限目标：库和表用户名和客户端主机用户密码

3、实战练习

  • 查看当前数据库用户情况
mysql> select user,host from mysql.user;
+--------+---------------+
| user   | host          |
+--------+---------------+
| root   | 127.0.0.1     |
| root   | ::1           |
| root   | hadoop-slave1 |
| root   | localhost     |
| system | localhost     |
+--------+---------------+
5 rows in set (0.00 sec)
  • 创建用户并授权
mysql> grant all privileges on test.* to 'admin'@'localhost' identified by 'admin123';
Query OK, 0 rows affected (0.01 sec)
  • 查看授权情况
mysql> select user,host from mysql.user;
+--------+---------------+
| user   | host          |
+--------+---------------+
| root   | 127.0.0.1     |
| root   | ::1           |
| root   | hadoop-slave1 |
| admin  | localhost     |
| root   | localhost     |
| system | localhost     |
+--------+---------------+
6 rows in set (0.00 sec)
  • 查看admin具体权限
mysql> show grants for 'admin'@'localhost';
+--------------------------------------------------------------------------------------------------------------+
| Grants for admin@localhost                                                                                   |
+--------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'admin'@'localhost' IDENTIFIED BY PASSWORD '*01A6717B58FF5C7EAFFF6CB7C96F7428EA65FE4C' |
| GRANT ALL PRIVILEGES ON `test`.* TO 'admin'@'localhost'                                                      |
+--------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

（二）create和grant配合使用

1、使用步骤

  • 创建用户username、主机localhost、密码passwd
mysql> create user 'username'@'localhost' identified by 'passwd';
  • 授权创建的用户管理dbname数据库权限（无需密码）
mysql> grant all privileges to dbname.* to 'username'@'localhost';

2、实战练习

  • 查看当前数据库用户情况
mysql> select user,host from mysql.user;
+--------+---------------+
| user   | host          |
+--------+---------------+
| root   | 127.0.0.1     |
| root   | ::1           |
| root   | hadoop-slave1 |
| admin  | localhost     |
| root   | localhost     |
| system | localhost     |
+--------+---------------+
6 rows in set (0.02 sec)
  • 创建用户
mysql> create user 'admin1'@'localhost' identified by 'admin123456';
Query OK, 0 rows affected (0.02 sec)

注意的是这一步并没有授权，仅仅是创建一个普通用户。

  • 查看用户情况
mysql> select user,host from mysql.user;
+--------+---------------+
| user   | host          |
+--------+---------------+
| root   | 127.0.0.1     |
| root   | ::1           |
| root   | hadoop-slave1 |
| admin  | localhost     |
| admin1 | localhost     |
| root   | localhost     |
| system | localhost     |
+--------+---------------+
7 rows in set (0.00 sec)

如果对admin1进行授权就参照步使用步骤的第二步完成。

（三）用户授权的权限有什么

1、查看用户权限

在上面授权过程中可以看出来，使用的基本都是全部权限：

grant all privileges to dbname.* to 'username'@'localhost';

然后查看用户的权限后是这样的：

mysql> show grants for 'admin'@'localhost';
+--------------------------------------------------------------------------------------------------------------+
| Grants for admin@localhost                                                                                   |
+--------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'admin'@'localhost' IDENTIFIED BY PASSWORD '*01A6717B58FF5C7EAFFF6CB7C96F7428EA65FE4C' |
| GRANT ALL PRIVILEGES ON `test`.* TO 'admin'@'localhost'                                                      |
+--------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

有时候并不需要给用户给这么多权限，那么怎么收回呢？

2、回收用户权限（revoke）

mysql> revoke insert on test.* from 'admin'@'localhost';  #一定要指定在那个数据库上的权限
Query OK, 0 rows affected (0.00 sec)

可以再次查看该用户的权限：

mysql> show grants for 'admin'@'localhos
+---------------------------------------------------------------------------------------------------------+
| Grants for admin@localhost                                                                         |
+---------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'admin'@'localhost' IDENTIFIED BY PASSWORD '*01A6717B58FF5C7EAFFF6CB7C96F7428EA65FE4C' |
| GRANT SELECT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE TEMPORARY TABLES,LOCK TABLES, EXECUTE,
 CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE, EVENT, TRIGGER ON `test`.* TO 'admin'@'localhost' |
+----------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

可以看到用户在test数据库上除了insert权限外的权限它都有了。

也就是说数据库的all priveleges包含下面的权限：

INSERT, 
SELECT, 
UPDATE, 
DELETE, 
CREATE, 
DROP,
REFERENCES, 
INDEX, 
ALTER, 
CREATE TEMPORARY TABLES,
LOCK TABLES, 
EXECUTE,
CREATE VIEW, 
SHOW VIEW,
CREATE ROUTINE,
ALTER ROUTINE,
EVENT, 
TRIGGER

所以我们在授权时尽量采用最小化的授权原则，比如：

mysql> grant select,insert,update,delete,create,drop on crm.* to 'admin'@'10.0.0.%' identified by '123456';

当admin用户创建表后记得收回create权限：

mysql> revoke create on crm.* from 'admin'@'10.0.0.0.%';

注意：可通过help revoke查看用法

二、远程连接

通过上面的授权，比如：…’admin1’@’localhost’..中的localhost是授权的主机，也就是说什么样的机器有权限连接MySQL服务器。 localhost可以用域名、IP地址、IP端来代替。

（一）匹配方式

1、百分号匹配法

mysql> grant all 0n dbname.* to 'admin1'@'10.0.0.%' identified by '123456';
mysql> flush privileges;

2、子网掩码配置法

mysql> grant all 0n dbname.* to 'admin1'@'10.0.0.0、255.255.255.0' identified by '123456';
mysql>flush privileges;

（二）客户端连接

客户端本地连接与远程连接是不一样的，如果远程连接首先应该赋予远程连接的权限：

mysql> grant all 0n dbname.* to 'admin1'@'10.0.0.%' identified by '123456';

其次，再进行远程连接：

mysql> mysql -uadmin1 -p123456 -h 10.0.0.0.3

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