MySQL 忘記root密碼的兩種處理方法
【背景】
由於各個原因，我遇到過不只一次用戶忘記了MySQL的root密碼；如果是普通用戶還好，我們可以用root用戶去改它的密碼，要命
的是把root給丟了！
對於MySQL來說如果你忘記了root密碼，但是你又想通過改密碼的方式把root密碼找回來的話，你就要作好重啟的準備了。
【方法一: skip_grant_tables + skip-networking 兩次重啟】
1): 第一步把MySQL給關掉
ps -ef | grep mysql mysql939 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 模式啟動 mysqld
/usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf --skip-grant-tables --skip-networking &
3): 進入mysql
如果是mysql-5.7的話密碼的hash值保存在了authentication_string這個列裏面，5.7之前的版本保存在password列裏面
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)
采用直接更新密碼hash值的方式來更新密碼
update mysql.user set authentication_string = password(‘MTls0352‘) where user=‘root‘; -- 更新密碼為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): 重啟mysqld
pkill mysql /usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf &
5): 用新的密碼進入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 + 一次重啟】
1): 創建用於修改root密碼的sql文件
touch /tmp/change_password.sql
內容如下
alter user root@‘127.0.0.1‘ identified by ‘mtls0352‘; alter user root@‘localhost‘ identified by ‘mtls0352‘;
2): 關閉mysql服務
pkill mysqld # 我的主機上只有一個mysql服務所以用pkill mysqld 沒有問題，如果你是單機多實例請用 kill $MYSQLPID
3): 代入修改密碼的init-file來啟動MySQL服務
/usr/local/mysql/bin/mysqld --init-file=/tmp/change_password.sql &
4): 用新密碼登錄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): 刪除修改密碼的sql文件
rm /tmp/change_password.sql
【我的評介】
a: 第一種方法比較傳統，第二種方法“角度刁鉆” 但是兩個都能解決問題；並且第二種方法看起來步驟又少一些，但是這並不只是問題的全部
通常一個線上的MySQL實例並不是以“/usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf &” 這樣直接下命令的方式啟動的，它們
通常和service ,systemctl 一起用的；所以這種情況下針對“方法二”還是要用service 或 systemctl把數據拉起來的，不然就不能用它們來管理
了，所以“方法二”最終也是要兩次重啟的。
b: 方法二能使用“alter user”語法，dba就可以不用care密碼到底保存在mysql.user表中的那個列。
兩種方法各有好處，所以重點還是要把一個方法搞的出神入畫！
【學習交流】
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MySQL 忘記root密碼的兩種處理方法