MySQL默认root密码查看与修改

1. 查看默认密码

MySQL 5.7 在初始安装后(CentOS7 操作系统)会生成随机初始密码，并在 /var/log/mysqld.log 中有记录，可以通过 cat 命令查看，找 password 关键字

[root@stg-mysql mysqldata]# sudo grep 'temporary password' /var/log/mysqld.log
2021-01-22T06:58:56.317416Z 5 [Note] [MY-010454] [Server] A temporary password is generated for 	root@localhost: Xq93pu;e&dO9

2. 如果使用默认密码登录不了，那么可以先关闭MySQL的登录密码校验

修改 /etc/my.cnf，在 [mysqld] 小节下添加一行：skip-grant-tables=1

让 mysqld 启动时不对密码进行验证

重启 mysqld 服务：systemctl restart mysqld
使用 root 用户登录到 mysql：mysql -u root

3. 修改/设置默认的root密码

mysql -u root -p

use mysql;

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '123456';   
# 123456是密码，root 是用户名

flush privileges;
quit;

若修改时报错：

ERROR 1290 (HY000): The MySQL server is running with the –skip-grant-tables option so it cannot execute this statement

解决方案：
```
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
```

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

原因是因为密码设置的过于简单会报错,MySQL有密码设置的规范，具体是与validate_password_policy的值有关,下图表明该值规则

解决方案：先查看密码规则，然后调整你的密码

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 (0.01 sec)

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