this information is important to all answers above : When you restart mysql server all policy config will be RESET and will be LOST, so to make your policy configuration PERSISTENT, you should follow these instructions: (tested on ubuntu server version 20.10)

用mysql应用这些变化后，洪阮回答 Sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf 加上最后一行:

[mysqld]
#
# * Basic Settings
#
..
..
..
validate_password.policy = LOW   # <== this line
..
..
# IMPORTANT notes: 
# - you can add more policy commands each by your needs.
# - notice the "." before "policy" , in some mysql versions is "_" , so be aware of that.

保存文件并重新启动mysql server: sudo service mysql restart 连接并检查配置的持久性: Sudo mysql -u your_username -p 显示像"validate_pass%"这样的变量; 结果应该是这样的:

+--------------------------------------+-------+
| Variable_name                        | Value |
+--------------------------------------+-------+
| validate_password.check_user_name    | ON    |
| validate_password.dictionary_file    |       |
| validate_password.length             | 6     |
| validate_password.mixed_case_count   | 1     |
| validate_password.number_count       | 0     |
| validate_password.policy             | LOW   |
| validate_password.special_char_count | 1     |
+--------------------------------------+-------+

我希望这能帮助到人们。

编辑:感谢@ahmednawazbutt:不要忘记FLUSH特权;

因为你的密码。你可以在MySQL客户端中使用以下查询查看密码验证配置指标:

SHOW VARIABLES LIKE 'validate_password%';

输出应该是这样的:

+--------------------------------------+-------+
| Variable_name                        | Value |
+--------------------------------------+-------+
| validate_password.check_user_name    | ON    |
| validate_password.dictionary_file    |       |
| validate_password.length             | 6     |
| validate_password.mixed_case_count   | 1     |
| validate_password.number_count       | 1     |
| validate_password.policy             | LOW   |
| validate_password.special_char_count | 1     |
+--------------------------------------+-------+

然后可以将密码策略级别设置低一些，例如:

SET GLOBAL validate_password.length = 6;
SET GLOBAL validate_password.number_count = 0;

查看MySQL文档。

有些时候，找到一个快速的解决方案是很棒的。但如果你能避免降低密码限制，它可以让你在未来的大头疼。

下一个链接来自官方文档https://dev.mysql.com/doc/refman/5.6/en/validate-password.html，在那里他们提供了一个与您的示例完全相同的示例，并解决了它。

唯一的问题是您的密码不够强，无法满足实际的最小策略(不建议删除)。所以你可以尝试不同的密码，就像你在例子中看到的那样。

最好的选择是通过你的密码策略，并设置相应的密码。您可以通过运行以下命令检查现有的密码验证插件系统变量的值

mysql> SHOW VARIABLES LIKE 'validate_password%';

通过操作系统变量来减少安全策略从来都不是一个好做法。

您可以从官方文档中阅读关于每个变量及其用例的详细信息，参考链接MySQL 5.6 MySQL 5.7 MySQL 8.0

this information is important to all answers above : When you restart mysql server all policy config will be RESET and will be LOST, so to make your policy configuration PERSISTENT, you should follow these instructions: (tested on ubuntu server version 20.10)

用mysql应用这些变化后，洪阮回答 Sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf 加上最后一行:

[mysqld]
#
# * Basic Settings
#
..
..
..
validate_password.policy = LOW   # <== this line
..
..
# IMPORTANT notes: 
# - you can add more policy commands each by your needs.
# - notice the "." before "policy" , in some mysql versions is "_" , so be aware of that.

保存文件并重新启动mysql server: sudo service mysql restart 连接并检查配置的持久性: Sudo mysql -u your_username -p 显示像"validate_pass%"这样的变量; 结果应该是这样的:

+--------------------------------------+-------+
| Variable_name                        | Value |
+--------------------------------------+-------+
| validate_password.check_user_name    | ON    |
| validate_password.dictionary_file    |       |
| validate_password.length             | 6     |
| validate_password.mixed_case_count   | 1     |
| validate_password.number_count       | 0     |
| validate_password.policy             | LOW   |
| validate_password.special_char_count | 1     |
+--------------------------------------+-------+

我希望这能帮助到人们。

编辑:感谢@ahmednawazbutt:不要忘记FLUSH特权;

如果你想设置一个空白密码。然后在MySQL客户端运行以下查询:

SET GLOBAL validate_password.check_user_name = No;
SET GLOBAL validate_password.dictionary_file = '';
SET GLOBAL validate_password.length = 0;
SET GLOBAL validate_password.mixed_case_count = 0;
SET GLOBAL validate_password.number_count = 0;
SET GLOBAL validate_password.policy = LOW;
SET GLOBAL validate_password.special_char_count = 0;

输出应该是这样的:

    SHOW VARIABLES LIKE 'validate_password%';

+--------------------------------------+-------+
| Variable_name                        | Value |
+--------------------------------------+-------+
| validate_password.check_user_name    | ON    |
| validate_password.dictionary_file    |       |
| validate_password.length             | 0     |
| validate_password.mixed_case_count   | 0     |
| validate_password.number_count       | 0     |
| validate_password.policy             | LOW   |
| validate_password.special_char_count | 0     |
+--------------------------------------+-------+

然后，您可以使用以下查询更新您的空白密码:

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '';