Linux Mysql 8.0.21忘记密码怎么处理？

1.停掉mysqld进程，修改配置文件后绕过权限校验启动
停掉服务：
service mysqld stop
修改配置文件：
vim /etc/my.cnf在[mysqld]下添加skip-grant-tables
启动服务：
service mysqld start

2.登录msyql，并修改密码
登录mysql:
mysql -uroot
修改密码：
alter user 'root'@'%' identified with mysql_native_password by '新密码';
flush privileges;
该操作成功后，表示root用户可以使用新密码远程连接数据库

3.去除配置文件中的skip-grant-tables，重新启动mysql

第三步可能遇到的问题
1.执行alter语句时，如下错，意思是密码太简单了，不符合规则

ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

2.查看规则
show variables like 'validate_password%';

mysql>  show variables like 'validate_password%';
+--------------------------------------+--------+
| Variable_name                        | Value  |
+--------------------------------------+--------+
| validate_password.check_user_name    | ON     |
| 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      |
+--------------------------------------+--------+
7 rows in set (0.00 sec)

上述变量含义如下

validate_password_dictionary_file
插件用于验证密码强度的字典文件路径。
validate_password_length
密码最小长度，参数默认为8，它有最小值的限制，最小值为：validate_password_number_count + validate_password_special_char_count + (2 * validate_password_mixed_case_count)
validate_password_mixed_case_count
密码至少要包含的小写字母个数和大写字母个数。
validate_password_number_count
密码至少要包含的数字个数。
validate_password_policy
密码强度检查等级，0/LOW、1/MEDIUM、2/STRONG。
默认是1，即MEDIUM，所以刚开始设置的密码必须符合长度，且必须含有数字，小写或大写字母，特殊字符。
validate_password_special_char_count
密码至少要包含的特殊字符数。

3.按照规则设置密码，或者修改规则
修改规则set global validate_password.mixed_case_count = 0;表示混合大小写字母个数改为0

4.有的小伙伴会遇到 show variables like 'validate_password%';结果为空，如下

show variables like 'validate_passwrod%';
Empty set (0.00 sec)

引用stackoverflow上的解决方案

This problem has happened because validate_password plugin is by default NOT activated. You can solve by these commands:
mysql> select plugin_name, plugin_status from information_schema.plugins where plugin_name like 'validate%';
Empty set (0.00 sec)
mysql> install plugin validate_password soname 'validate_password.so';
Query OK, 0 rows affected (0.02 sec)
mysql> select plugin_name, plugin_status from information_schema.plugins where plugin_name like 'validate%';
Finally, you will show the following:

+-------------------+---------------+
| plugin_name       | plugin_status |
+-------------------+---------------+
| validate_password | ACTIVE        |
+-------------------+---------------+
1 row in set (0.00 sec)

Then you can run your command:
mysql> SHOW VARIABLES LIKE 'validate_password%';

+--------------------------------------+--------+
| Variable_name                        | Value  |
+--------------------------------------+--------+
| validate_password_check_user_name    | 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      |
+--------------------------------------+--------+
7 rows in set (0.00 sec).