网上有很多关于忘记MySQL root密码的一些文章，里面都有写怎么去解决，但有时觉得写得太恶心，要么一字不漏的抄别人的，要么就说得不清不楚，好了，不吐槽了，以下是解决的整个过程。

首先我们要知道忘记MySQL root密码后，能否重启mysql，能重启的操作是怎么样的？不能重启的操作又会是怎么样的？

情况一：(能重启情况下)

修改my.cnf配置文件，在mysqld栏下添加skip-grant-tables选项，意思是mysqld server启动之后并不使用权限系统(privilege system)，也可以理解为跳过授权表。为了安全起见，通常加上skip-networking，mysqld不侦听任何TCP/IP连接请求。

重启mysqld，然后空密码连接：

[root ~]$mysql -uroot -S /data/mysql-5.5/mysql.sock

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection idis 3Server version:5.5.40-log MySQL Community Server (GPL)

Copyright (c)2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracleis 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>

可以看到已经成功登录了，然后修改root密码：

mysql> update mysql.user set password=password('123456') where user='root';

Query OK,4 rows affected (0.00sec)

Rows matched:4 Changed: 4 Warnings: 0mysql> flush privileges;

Query OK, 0 rows affected (0.01 sec)

已经成功修改密码了，但还有事情要做，就是把刚刚添加到my.cnf里的skip-grant-tables和skip-networking删除掉或者注释掉。

情况二：(不能重启mysql的情况)

如果不能重启，mysql.user 刚好有权限比较低的用户，如果没有，你请神仙来帮你吧，哈哈

1、为了测试，我自己创建一个用户，可以没什么权限

mysql> create user xuanzhi@'localhost' identified by '123456';

Query OK,0 rows affected (0.00 sec)

2、进到数据目录下：

[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、用权限比较小的用户登录：

[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 connectionid is 3Server 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 clearthe current input statement.

mysql>use test

Database changed

mysql> update user set password=password('123123') where user='root';

Query OK,4 rows affected (0.00sec)

Rows matched:4 Changed: 4 Warnings: 0

4、把修改后的user.MYD和user.MYI复制到mysql目录下，记得备份之前的文件。

[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进程号，并且发送SIGHUP信号，重新加载权限表。(有时加载一次不行的时候，再加载多一次@。@)

[root mysql]$ pgrep -n mysql23166[root mysql]$kill -SIGHUP 23166[root mysql]$/usr/local/mysql-5.5.40/bin/mysql -uroot -p123123 -S /data/mysql-5.5/mysql.sock

ERROR1045 (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 connectionid is 5Server 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 clearthe current input statement.

mysql>

不重启的第二种方法：

1、创建新的数据目录，并给原来user相应的权限,忘记密码对应的实例它的user是mysql，所以把权限给mysql用户

[root data]$ mkdir -pv /dbdata/datadir/

mkdir: 已创建目录 "/dbdata"

mkdir: 已创建目录 "/dbdata/datadir/"[root data]$chown -R mysql:mysql /dbdata/datadir/

2、执行初始化操作：(报错了)

[root scripts]$ pwd

/usr/local/mysql-5.5.40/scripts

[root scripts]$ ./mysql_install_db --datadir=/dbdata/datadir/ --user=mysql2

FATAL ERROR: Could notfind ./bin/my_print_defaults

If you compiled from source, you need to run'make install'to

copy the software into the correct location readyforoperation.

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.

解决方法：

[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 ina future release.

OK

Filling help tables...141210 16:09:24 [Warning] 'THREAD_CONCURRENCY' is deprecated and will be removed ina future release.

OK

3、启动一个新的进程，这里要注意一下port，sock文件，还有pid文件，这都是新的，user还是忘记密码实例的user，而不是忘记密码对应的那个数据库实例的，这里我们不需要用到InnoDB引擎,设置默认引擎为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、登录新启动的mysql实例，此时密码为空密码：

root datadir]$ /usr/local/mysql-5.6.10/bin/mysql -S /dbdata/datadir/mysql2.sock

Welcometo the MySQL monitor. Commands end with ; or\g.

Your MySQL connection idis 1Server version:5.6.10-logSource distribution

Copyright (c)2000, 2013, Oracle and/or its affiliates. Allrights reserved.

Oracleis a registered trademark of Oracle Corporation and/orits

affiliates. Other names may be trademarksoftheir respective

owners.

Type'help;' or '\h' for help. Type '\c' to clear the currentinput statement.

mysql>flush tables;

Query OK,0 rows affected (0.00 sec)

修改root密码：

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 (0.02sec)

mysql> update mysql.user set password=password('654321') where user='root';

Query OK,4 rows affected (0.03sec)

Rows matched:4 Changed: 4 Warnings: 0mysql> flush privileges;

Query OK,0 rows affected (0.00 sec)

5、拷备新的user表到忘记密码的实例数据库的mysql目录下

[root mysql]$ pwd

/dbdata/datadir/mysql

[root mysql]$cp user.* /data/mysql-5.6/mysql/

cp：是否覆盖"/data/mysql-5.6/mysql/user.frm"？ ycp：是否覆盖"/data/mysql-5.6/mysql/user.MYD"？ ycp：是否覆盖"/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、我们需要到mysqld发送一个sighup信号，MySQL响应这个信号加载授权表，刷新表，日志，线程缓存。

如果是单个MySQL实例，可以用这样的方法去重新加载

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

如果是多个MySQL实例在一台服务器上的话，就要注意点了，可以通过这样的方法找到pid，我旧实例的端口是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

tcp0 0 0.0.0.0:3307 0.0.0.0:* LISTEN 8414/mysqld

tcp0 0 0.0.0.0:3308 0.0.0.0:* LISTEN 6430/mysqld

tcp0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1144/sshdtcp0 0 :::3310 :::* LISTEN 17151/mysqld

tcp0 0 :::22 :::* LISTEN 1144/sshd

tcp0 0 ::1:631 :::* LISTEN 1109/cupsd

tcp0 0 :::3306 :::* LISTEN 2091/mysqld[root mysql-5.6.10]$ kill -1 2091

有时kill -1一次不行，再执行一次就可以了：

[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.

ERROR1045 (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 connectionid is 13Server 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 clearthe current input statement.

mysql>

OK，已经成功登录了，如果有更多好的方法，我们可以再一起讨论下

总结：

1)第一种方法简单，但需要重启MySQL,重启会影响线上业务，一般不建议重启

2)第二种方法比较好，不用重启MySQL实例，修改密码，只修改root用户的，而且其它保持不变

3)第三种方法也不需要重启，但是新的user表里，只有root一个用户，如果之前服务器还存在别的用户及权限，这就比较麻烦了

PS:本人也是参考别人的博客做的，但我没有照搬别人的东西，太恶心了，希望大家有自己的风格。^.^

作者：陆炫志

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