MySQL 忘记 root密码 两种 处理方法

原文：MySQL 忘记root密码的两种处理方法 - 走看看 (zoukankan.com)

【背景】

　　由于各个原因，我遇到过不只一次我服务的客户忘记了MySQL的root密码；如果是普通用户还好，我们可以用root用户去改它的密码，要命

　　的是把root给丢了！

　　对于MySQL来说如果你忘记了root密码，但是你又想通过改密码的方式把root密码找回来的话，你就要作好重启的准备了。

【方法一: --skip_grant_tables  --skip-networking   两次重启】

　　1): 第一步把MySQL给关掉

ps -ef | grep mysql                                                            
mysql       939      1  0 16:39 ?        00:00:02 /usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf
kill -9 939

　　2): 以 --skip-grant-tables --skip-networking 模式启动 mysqld

/usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf --skip-grant-tables --skip-networking &

　　3): 进入mysql

　　如果是mysql-5.7的话密码的 hash 值保存在了 authentication_string 这个列里面，5.7之前的版本保存在 password 列里面

select user,host,authentication_string from mysql.user;
+---------------+-----------+-------------------------------------------+
| user          | host      | authentication_string                     |
+---------------+-----------+-------------------------------------------+
| root          | localhost | *91B73478B18B04D13F6926FAB5A6178250EAB697 |
| mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| monitor       | 127.0.0.1 | *DAD735712BB263A8DA12A091AABC625FE99DD344 |
| root          | 127.0.0.1 | *91B73478B18B04D13F6926FAB5A6178250EAB697 |
| backup        | 127.0.0.1 | *2139A3EF5FE5A0229BE550AD5ED2947B07F43B93 |
| backup        | localhost | *2139A3EF5FE5A0229BE550AD5ED2947B07F43B93 |
| appuser       | 127.0.0.1 | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+---------------+-----------+-------------------------------------------+
8 rows in set (0.01 sec)

　　采用直接更新密码 hash 值的方式来更新密码

update mysql.user set authentication_string = password('MTls0352') where user='root'; 
-- 更新密码为MTls0352
Query OK, 2 rows affected, 1 warning (1.01 sec)
Rows matched: 2  Changed: 2  Warnings: 1

select user,host,authentication_string from mysql.user;
+---------------+-----------+-------------------------------------------+
| user          | host      | authentication_string                     |
+---------------+-----------+-------------------------------------------+
| root          | localhost | *597B32612905C92ABC495354FC276D24D0A541C1 |
| mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| monitor       | 127.0.0.1 | *DAD735712BB263A8DA12A091AABC625FE99DD344 |
| root          | 127.0.0.1 | *597B32612905C92ABC495354FC276D24D0A541C1 |
| backup        | 127.0.0.1 | *2139A3EF5FE5A0229BE550AD5ED2947B07F43B93 |
| backup        | localhost | *2139A3EF5FE5A0229BE550AD5ED2947B07F43B93 |
| appuser       | 127.0.0.1 | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+---------------+-----------+-------------------------------------------+
8 rows in set (0.00 sec)

　　4): 重启 mysqld

pkill mysql
/usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf &

　　5): 用新的密码进入MySQL

mysql  -uroot -pMTls0352                                                    
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 2
Server version: 5.7.23-log 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> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION        |
+---------------------------------------------------------------------+
2 rows in set (0.01 sec)

　　

【方法二：init-file   一次重启】

　　1): 创建用于修改root密码的sql文件

touch /tmp/change_password.sql

　　内容如下

alter user root@'127.0.0.1' identified by 'mtls0352';
alter user root@'localhost' identified by 'mtls0352';

　　2): 关闭mysql服务

pkill mysqld # 我的主机上只有一个mysql服务所以用 pkill mysqld 没有问题，
如果你是单机多实例请用 kill $MYSQLPID

　　3): 代入修改密码的init-file来启动MySQL服务

/usr/local/mysql/bin/mysqld --init-file=/tmp/change_password.sql &

　　4): 用新密码登录MySQL

mysql -uroot -pmtls0352                                              
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 3
Server version: 5.7.23-log 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> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION        |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)

　　5): 删除修改密码的sql文件

rm /tmp/change_password.sql
　 第一种方法比较传统，第二种方法“角度刁钻” ，看起来步骤少一些，但是一个线上的MySQL实例不是以
“/usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf &” 这样命令的方式启动的，
如果要用 service ,systemctl 来管理，“方法二”最终也是要两次重启，
使用“alter user”语法，不关心密码到底保存在mysql.user表中的那个列。