MySQL忘记密码了怎么解决

笔者曾经有一次误删了mysqlroot用户，怎么办？

之前的解决方式是通过忽略授权表的方式重启mysql然后插入相关数据解决该问题的，但是这种方式需要重启mysql，会影响现有业务，那么有没有其他方式可以不重启MySQL就解决呢?

因为mysql的user表示MyISAM引擎的，因此我们可以通过修改对应的文件来解决这个问题。下面是本人在测试环境的一次演练，仅供参考。

一、查看现有用户

04:18:34 root@localhost [mysql]>select user,host from user;
+---------------+-----------+
| user          | host      |
+---------------+-----------+
| mysql.session | localhost |
| mysql.sys     | localhost |
| root          | localhost |
+---------------+-----------+
3 rows in set (0,00 sec)

二、删除本地root用户

04:18:59 root@localhost [mysql]>drop user root@'localhost';

三、再次查看用户

04:20:02 root@localhost [mysql]>select user,host from user;
+---------------+-----------+
| user          | host      |
+---------------+-----------+
| mysql.session | localhost |
| mysql.sys     | localhost |
+---------------+-----------+

现在我们开始恢复用户数据

四、移动user表相关文件

[root@localhost mysql]# cp user.* /vagrant/mysql/3307/data/test/

五、登录另一个实例并查看user表

04:23:53 root@localhost [(none)]>use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
04:23:56 root@localhost [test]>show tables;
+----------------+
| Tables_in_test |
+----------------+
| user           |
+----------------+
1 row in set (0,00 sec)

04:23:58 root@localhost [test]>select * from user\G
*************************** 1. row ***************************
                  Host: localhost
                  User: mysql.session
           Select_priv: N
           Insert_priv: N
           Update_priv: N
           Delete_priv: N
           Create_priv: N
             Drop_priv: N
           Reload_priv: N
         Shutdown_priv: N
          Process_priv: N
             File_priv: N
            Grant_priv: N
       References_priv: N
            Index_priv: N
            Alter_priv: N
          Show_db_priv: N
            Super_priv: Y
 Create_tmp_table_priv: N
      Lock_tables_priv: N
          Execute_priv: N
       Repl_slave_priv: N
      Repl_client_priv: N
      Create_view_priv: N
        Show_view_priv: N
   Create_routine_priv: N
    Alter_routine_priv: N
      Create_user_priv: N
            Event_priv: N
          Trigger_priv: N
Create_tablespace_priv: N
              ssl_type:
            ssl_cipher:
           x509_issuer:
          x509_subject:
         max_questions: 0
           max_updates: 0
       max_connections: 0
  max_user_connections: 0
                plugin: mysql_native_password
 authentication_string: *C7A1AAE2D250AFD864050FAF4935EF6F5D185A92
      password_expired: N
 password_last_changed: 2018-02-23 13:19:12
     password_lifetime: NULL
        account_locked: Y
*************************** 2. row ***************************
                  Host: localhost
                  User: mysql.sys
           Select_priv: N
           Insert_priv: N
           Update_priv: N
           Delete_priv: N
           Create_priv: N
             Drop_priv: N
           Reload_priv: N
         Shutdown_priv: N
          Process_priv: N
             File_priv: N
            Grant_priv: N
       References_priv: N
            Index_priv: N
            Alter_priv: N
          Show_db_priv: N
            Super_priv: N
 Create_tmp_table_priv: N
      Lock_tables_priv: N
          Execute_priv: N
       Repl_slave_priv: N
      Repl_client_priv: N
      Create_view_priv: N
        Show_view_priv: N
   Create_routine_priv: N
    Alter_routine_priv: N
      Create_user_priv: N
            Event_priv: N
          Trigger_priv: N
Create_tablespace_priv: N
              ssl_type:
            ssl_cipher:
           x509_issuer:
          x509_subject:
         max_questions: 0
           max_updates: 0
       max_connections: 0
  max_user_connections: 0
                plugin: mysql_native_password
 authentication_string: *C7A1AAE2D250AFD864050FAF4935EF6F5D185A92
      password_expired: N
 password_last_changed: 2018-02-23 13:19:26
     password_lifetime: NULL
        account_locked: Y
2 rows in set (0,00 sec)

六、把本实例的root用户插入刚刚移动过来的user表

04:25:03 root@localhost [test]>insert into user select * from mysql.user where user = 'root' and host ='localhost';
Query OK, 1 row affected (0,02 sec)
Records: 1  Duplicates: 0  Warnings: 0

七、再次移动user文件到原先的位置

[root@localhost test]# cp user.* /vagrant/mysql/3306/data/mysql

八、重新加载配置到内存

[root@localhost test]# kill -HUP `pidof mysqld`

通过该步mysql并不会重启，对应用不会有影响

九、重新登录，OK

[root@localhost test]# mysql -uroot -p -S /tmp/mysql3306.sock
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 5.7.21-log MySQL Community Server (GPL)

Copyright (c) 2000, 2017, 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.

04:30:57 root@localhost [(none)]>