我这里是通过mysql官方的yum源来安装的mysql-community-server ，当前版本是MySQL 5.7.12 。
wget rpm -ivh mysql57-community-release-el6-8.noarch.rpm yum install mysql-community-server service mysqld start
第一次启动后会有个初始化的过程，会产生root账户的随机密码。
为了加强安全性，MySQL5.7为root用户随机生成了一个密码，在error_log中，关于error_log的位置，如果安装的是RPM包，则默认是 /var/log/mysqld.log 。
找到生成的随机密码
mysql -u root -p‘zXMgg%#L3=;1‘ mysql: [Warning] Using a password on the command line interface can be insecure. Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 4 Server version: 5.7.12 Copyright (c) 2000, 2016, 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> show databases; ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement. mysql> show databases; ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
登陆上过后，进行正常操作会受限，提示你必须修改密码后才能进行操作。
好吧，根据提示修改密码：
mysql> SET PASSWORD = PASSWORD(‘123456‘);
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
mysql> SET PASSWORD = PASSWORD("root");
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
但是提示根据当前密码策略，设置的密码不允许。
查阅官方文档后发现有以下三种密码策略：
| Policy | Tests Performed |
0 or LOW |
Length |
1 or MEDIUM |
Length; numeric, lowercase/uppercase, and special characters |
2 or STRONG |
Length; numeric, lowercase/uppercase, and special characters; dictionary file |
当前密码策略默认为1 也就是 MEDIUM
mysql [email protected]:(none)> show VARIABLES like "%password%" +---------------------------------------+---------+ | Variable_name | Value | |---------------------------------------+---------| | default_password_lifetime | 0 | | disconnect_on_expired_password | ON | | log_builtin_as_identified_by_password | OFF | | mysql_native_password_proxy_users | OFF | | old_passwords | 0 | | report_password | | | sha256_password_proxy_users | OFF | | validate_password_dictionary_file | | | validate_password_length | 8 | | validate_password_mixed_case_count | 1 | | validate_password_number_count | 1 | | validate_password_policy | MEDIUM | | validate_password_special_char_count | 1 | +---------------------------------------+---------+ 13 rows in set Time: 0.030s
所以你更改密码的策略是 数字 小写字母 大写字母 特殊字符 长度至少8位 。
更改完密码就可以进行数据库的操作了。
mysql [email protected]:(none)> show DATABASES; +--------------------+ | Database | |--------------------| | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set Time: 0.009s
接下来修改默认密码策略（当然实际环境是不推荐修改为更低安全策略的）
mysql [email protected]:(none)> set global validate_password_policy = 0; Query OK, 0 rows affected Time: 0.003s
现在设置完默认密码策略后，就只有 密码长度限制 了。默认为字符长度至少8位。
其中：
validate_password_number_count指定了密码中数据的长度，
validate_password_special_char_count指定了密码中特殊字符的长度，
validate_password_mixed_case_count指定了密码中大小字母的长度。
这些参数，默认值均为1，所以validate_password_length最小值为4，如果你显性指定validate_password_length的值小于4，尽管不会报错，但validate_password_length的值将设为4。
mysql [email protected]:(none)> set global validate_password_length = 3; Query OK, 0 rows affected Time: 0.004s mysql [email protected]:(none)> show VARIABLES like "validate_password_length" +--------------------------+---------+ | Variable_name | Value | |--------------------------+---------| | validate_password_length | 4 | +--------------------------+---------+ 1 row in set Time: 0.010s
如果修改了validate_password_number_count，validate_password_special_char_count，validate_password_mixed_case_count中任何一个值，则validate_password_length将进行动态修改。
MySQL 5.7 默认安装了 validate_password 插件。 所以多了以上步骤。
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通过my.cnf 配置文件设置密码策略的级别
"/etc/my.cnf" 28L, 987C 22,1 All # For advice on how to change settings please see # http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html [mysqld] # # Remove leading # and set to the amount of RAM for the most important data # cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%. # innodb_buffer_pool_size = 128M # # Remove leading # to turn on a very important data integrity option: logging # changes to the binary log between backups. # log_bin # # Remove leading # to set options mainly useful for reporting servers. # The server defaults are faster for transactions and fast SELECTs. # Adjust sizes as needed, experiment to find the optimal values. # join_buffer_size = 128M # sort_buffer_size = 2M # read_rnd_buffer_size = 2M datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock validate_password_policy=2
最后一行 validate_password_policy 设置mysql启动的时候密码策略级别。 如果设置为3 ，那么需要指定字典文件。
当然你也可以通过 my.cnf 配置文件关闭 validate_password 插件。
只需要添加一行
validate_password = off
编辑完配置文件后，重启mysqld服务即可生效。
mysql [email protected]:(none)> show VARIABLES like "validate_password%" +-----------------+---------+ | Variable_name | Value | |-----------------+---------| +-----------------+---------+ 0 rows in set Time: 0.008s
关闭validate_password插件后，就没有了validate_password的一些参数变量。
MySQL官方对于 validate_password 插件的使用介绍：
http://dev.mysql.com/doc/refman/5.6/en/validate-password-plugin.html#option_mysqld_validate-password
.