網上有很多關于忘記MySQL root密碼的一些文章，里面都有寫怎么去解決，但有時覺得寫得太惡心，要么一字不漏的抄別人的，要么就說得不清不楚，好了，不吐槽了，以下是解決的整個過程。

首先我們要知道忘記MySQL root密碼后，能否重啟mysql，能重啟的操作是怎么樣的？不能重啟的操作又會是怎么樣的？

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情況一：（能重啟情況下）

修改my.cnf配置文件，在mysqld欄下添加skip-grant-tables選項，意思是mysqld server啟動之后并不使用權限系統（privilege system），也可以理解為跳過授權表。為了安全起見，通常加上skip-networking，mysqld不偵聽任何TCP/IP連接請求。

重啟mysqld，然后空密碼連接：

[root ~]$mysql -uroot -S /data/mysql-5.5/mysql.sock Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.5.40-log MySQL Community Server (GPL)Copyright (c) 2000, 2014, 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>

可以看到已經成功登錄了，然后修改root密碼：

mysql> update mysql.user set password=password('123456') where user='root'; Query OK, 4 rows affected (0.00 sec) Rows matched: 4 Changed: 4 Warnings: 0 mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

已經成功修改密碼了，但還有事情要做，就是把剛剛添加到my.cnf里的skip-grant-tables和skip-networking刪除掉或者注釋掉。

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情況二：(不能重啟mysql的情況)

如果不能重啟，mysql.user 剛好有權限比較低的用戶，如果沒有，你請神仙來幫你吧，哈哈

1、為了測試，我自己創建一個用戶，可以沒什么權限

mysql> create user xuanzhi@'localhost' identified by '123456'; Query OK, 0 rows affected (0.00 sec)

2、進到數據目錄下：

[root mysql-5.5]$ pwd /data/mysql-5.5 [root mysql-5.5]$ cp mysql/user.* test/ [root mysql-5.5]$ chown mysql.mysql test/user.*

3、用權限比較小的用戶登錄：

[root mysql-5.5]$mysql -uxuanzhi -p123456 -S /data/mysql-5.5/mysql.sock Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.5.40-log MySQL Community Server (GPL)Copyright (c) 2000, 2014, 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> use test Database changed mysql> update user set password=password('123123') where user='root'; Query OK, 4 rows affected (0.00 sec) Rows matched: 4 Changed: 4 Warnings: 0

4、把修改后的user.MYD和user.MYI復制到mysql目錄下，記得備份之前的文件。

[root mysql-5.5]$ pwd /data/mysql-5.5 [root mysql-5.5]$ mv mysql/user.MYD mysql/user.MYD.bak [root mysql-5.5]$ mv mysql/user.MYI mysql/user.MYI.bak [root mysql-5.5]$ cp test/user.MY* mysql/ [root mysql-5.5]$ chown mysql:mysql mysql/user.*

5.查找mysql進程號，并且發送SIGHUP信號，重新加載權限表。（有時加載一次不行的時候，再加載多一次@。@）

[root mysql]$ pgrep -n mysql 23166 [root mysql]$ kill -SIGHUP 23166 [root mysql]$ /usr/local/mysql-5.5.40/bin/mysql -uroot -p123123 -S /data/mysql-5.5/mysql.sock ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES) [root mysql]$ kill -SIGHUP 23166 [root mysql]$ /usr/local/mysql-5.5.40/bin/mysql -uroot -p123123 -S /data/mysql-5.5/mysql.sock Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 5 Server version: 5.5.40-log MySQL Community Server (GPL)Copyright (c) 2000, 2014, 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>

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不重啟的第二種方法：

1、創建新的數據目錄，并給原來user相應的權限,忘記密碼對應的實例它的user是mysql，所以把權限給mysql用戶

[root data]$ mkdir -pv /dbdata/datadir/ mkdir: 已創建目錄 "/dbdata" mkdir: 已創建目錄 "/dbdata/datadir/" [root data]$ chown -R mysql:mysql /dbdata/datadir/

2、執行初始化操作：（報錯了）

[root scripts]$ pwd /usr/local/mysql-5.5.40/scripts [root scripts]$ ./mysql_install_db --datadir=/dbdata/datadir/ --user=mysql2FATAL ERROR: Could not find ./bin/my_print_defaultsIf you compiled from source, you need to run 'make install' to copy the software into the correct location ready for operation.If you are using a binary release, you must either be at the top level of the extracted archive, or pass the --basedir option pointing to that location.

解決方法：

[root scripts]$ /usr/local/mysql-5.6.10/scripts/mysql_install_db --datadir=/dbdata/datadir/ --user=mysql --datadir=/dbdata/datadir/ --basedir=/usr/local/mysql-5.6.10/ Installing MySQL system tables... 141210 16:09:24 [Warning] 'THREAD_CONCURRENCY' is deprecated and will be removed in a future release. OK Filling help tables... 141210 16:09:24 [Warning] 'THREAD_CONCURRENCY' is deprecated and will be removed in a future release. OK

3、啟動一個新的進程，這里要注意一下port，sock文件，還有pid文件，這都是新的，user還是忘記密碼實例的user，而不是忘記密碼對應的那個數據庫實例的，這里我們不需要用到InnoDB引擎,設置默認引擎為MyISAM：

[root ~]$? /usr/local/mysql-5.6.10/bin/mysqld_safe --datadir=/dbdata/datadir --plugin-dir=/usr/local/mysql-5.6.10/lib/plugin/? --skip-innodb \
> --default-storage-engine=myisam --socket=/dbdata/datadir/mysql2.sock --user=mysql --port=3305 --log-error=/dbdata/datadir/error2.log --pid-file=/data/mysql-5.6/mysql.pid &
[1] 21204
[root ~]$ 141210 16:56:11 mysqld_safe Logging to '/dbdata/datadir/error2.log'. 141210 16:56:11 mysqld_safe Starting mysqld daemon with databases from /dbdata/datadir

4、登錄新啟動的mysql實例，此時密碼為空密碼：

root datadir]$ /usr/local/mysql-5.6.10/bin/mysql -S /dbdata/datadir/mysql2.sock Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 Server version: 5.6.10-log Source distributionCopyright (c) 2000, 2013, 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> flush tables; Query OK, 0 rows affected (0.00 sec)

修改root密碼：

mysql> select user, host, password from user where user like 'root'; +------+-----------------------+----------+ | user | host | password | +------+-----------------------+----------+ | root | localhost | | | root | localhost.localdomain | | | root | 127.0.0.1 | | | root | ::1 | | +------+-----------------------+----------+ 4 rows in set (0.02 sec)mysql> update mysql.user set password=password('654321') where user='root'; Query OK, 4 rows affected (0.03 sec) Rows matched: 4 Changed: 4 Warnings: 0 mysql> flush privileges; Query OK, 0 rows affected (0.00 sec)

5、拷備新的user表到忘記密碼的實例數據庫的mysql目錄下

[root mysql]$ pwd /dbdata/datadir/mysql [root mysql]$ cp user.* /data/mysql-5.6/mysql/ cp：是否覆蓋"/data/mysql-5.6/mysql/user.frm"？ y cp：是否覆蓋"/data/mysql-5.6/mysql/user.MYD"？ y cp：是否覆蓋"/data/mysql-5.6/mysql/user.MYI"？ y [root mysql]$ chown -R mysql5.6:mysql5.6 /data/mysql-5.6/ [root mysql]$ chmod 660 /data/mysql-5.6/mysql/user.*

6、我們需要到mysqld發送一個sighup信號，MySQL響應這個信號加載授權表，刷新表，日志，線程緩存。
如果是單個MySQL實例，可以用這樣的方法去重新加載

[root ~]$ kill -1 $(/sbin/pidof mysqld)

如果是多個MySQL實例在一臺服務器上的話，就要注意點了，可以通過這樣的方法找到pid，我舊實例的端口是3306：

[root mysql-5.6.10]$ netstat -nltp Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:3307 0.0.0.0:* LISTEN 8414/mysqld tcp 0 0 0.0.0.0:3308 0.0.0.0:* LISTEN 6430/mysqld tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1144/sshd tcp 0 0 :::3310 :::* LISTEN 17151/mysqld tcp 0 0 :::22 :::* LISTEN 1144/sshd tcp 0 0 ::1:631 :::* LISTEN 1109/cupsd tcp 0 0 :::3306 :::* LISTEN 2091/mysqld [root mysql-5.6.10]$ kill -1 2091

有時kill -1一次不行，再執行一次就可以了：

[root mysql-5.6.10]$ kill -1 2091 [root mysql-5.6.10]$ /usr/local/mysql-5.6.10/bin/mysql -uroot -p654321 -S /data/mysql-5.6/mysql.sock Warning: Using a password on the command line interface can be insecure. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES) [root mysql-5.6.10]$ kill -1 2091 [root mysql-5.6.10]$ /usr/local/mysql-5.6.10/bin/mysql -uroot -p654321 -S /data/mysql-5.6/mysql.sock 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 13 Server version: 5.6.10-log MySQL Community Server (GPL)Copyright (c) 2000, 2013, 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>

OK，已經成功登錄了，如果有更多好的方法，我們可以再一起討論下

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總結：

1）第一種方法簡單，但需要重啟MySQL,重啟會影響線上業務，一般不建議重啟

2）第二種方法比較好，不用重啟MySQL實例，修改密碼，只修改root用戶的，而且其它保持不變

3）第三種方法也不需要重啟，但是新的user表里，只有root一個用戶，如果之前服務器還存在別的用戶及權限，這就比較麻煩了

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?參考資料：http://www.percona.com/blog/2014/12/10/recover-mysql-root-password-without-restarting-mysql-no-downtime/

PS:本人也是參考別人的博客做的，但我沒有照搬別人的東西，太惡心了，希望大家有自己的風格。^.^

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作者：陸炫志 出處：xuanzhi的博客 http://www.cnblogs.com/xuanzhi201111 您的支持是對博主最大的鼓勵，感謝您的認真閱讀。本文版權歸作者所有，歡迎轉載，但請保留該聲明。

轉載于:https://www.cnblogs.com/xuanzhi201111/p/4138352.html

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