实战-MySQL8.0版本忘记密码怎么办？
1.修改MySQL的登录设置，加上skip-grant-tables，跳过登录权限验证
[root@centos-7 ~]# vim /data/mysql8.0.20/mysql3306/tmp/mysql3306.cnf [mysqld]
port=3306
socket=/tmp/mysql3306.sock
basedir=/usr/local/mysql8.0.20
datadir=/data/mysql8.0.20/mysql3306/data
tmpdir=/data/mysql8.0.20/mysql3306/tmp
plugin-load-add=mysql_clone.so
clone=FORCE_PLUS_PERMANENT
skip-grant-tables
2.重启数据库，由于我忘记密码了，无法正常使用mysqladmin -S /tmp/mysql3306.sock -uroot -p shutdown命令关闭mysql服务，我直接kill掉后台3306数据库进程，由于是通过mysqld_safe启动的，所以kill掉之后会重启，也达到了重新加载配置文件的目的（也可以先杀掉mysqld_safe进程，再杀死3306数据库进程，这样可以停掉3306数据库线程）
[root@centos-7 ~]# kill -9 22365
[root@centos-7 ~]# /usr/local/mysql8.0.20/bin/mysqld_safe: 行 199: 22365 已杀死 env MYSQLD_PARENT_PID=21997 nohup /usr/local/mysql8.0.20/bin/mysqld --defaults-file=/data/mysql8.0.20/mysql3306/tmp/mysql3306.cnf --basedir=/usr/local/mysql8.0.20 --datadir=/data/mysql8.0.20/mysql3306/data --plugin-dir=/usr/local/mysql8.0.20/lib/plugin --user=mysql --log-error=/data/mysql8.0.20/mysql3306/logs/mysql_error.log --pid-file=centos-7.shared.pid --socket=/tmp/mysql3306.sock --port=3306 < /dev/null > /dev/null 2>&1
2020-07-13T22:55:17.642239Z mysqld_safe Number of processes running now: 0
2020-07-13T22:55:17.650764Z mysqld_safe mysqld restarted
3.登录数据库
[root@centos-7 ~]# mysql -S /tmp/mysql3306.sock
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 8.0.20 MySQL Community Server - GPL
Copyright (c) 2000, 2018, 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>
4.将密码置空（Tips：①不能直接修改为其他密码，亲测修改后无法登录，提示无权限；②MySQL5.7.6版本后废弃user表中的password字段和password()方法，所以旧方法重置密码对MySQL8.0行不通；③直接alter会报错）
mysql> update user set authentication_string = '' where user = 'root';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
5.删除掉第一步在配置文件加的skip-grant-tables
6.重启数据库
7.登录（使用空密码，第四步已置空）
[root@centos-7 ~]# mysql -S /tmp/mysql3306.sock -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.20 MySQL Community Server - GPL
Copyright (c) 2000, 2018, 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>
9.修改密码
mysql> alter user 'root'@'localhost' identified by 'Root!2020';
Query OK, 0 rows affected (0.02 sec)
10.退出，验证下修改后的密码
mysql> quit
Bye
[root@centos-7 ~]# mysql -S /tmp/mysql3306.sock -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.20 MySQL Community Server - GPL
Copyright (c) 2000, 2018, 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>
重置密码成功！