排障集合———忘记原密码，如何重新修改MySQL登入密码

忘记密码，无法登入数据库

root@localhost ~]# mysql -uroot -p    //密码输入错误，无法登入
Enter password: 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
[root@localhost ~]# mysqladmin -u root -p password '123456'  //忘记原始密码，也无法靠mysqladmin修改密码方式登入
Enter password: 
mysqladmin: connect to server at 'localhost' failed
error: 'Access denied for user 'root'@'localhost' (using password: YES)'

解决办法

[root@localhost ~]# vi /etc/my.cnf   //修改配置
[mysqld]
……省略部分
skip-grant-tables   //插入空授权登入配置
[root@localhost ~]# systemctl restart mysqld   //重启MySQL
[root@localhost ~]# mysql -uroot -p
Enter password:     //直接回车，登入成功
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.20 Source distribution
……省略部分
mysql> 
mysql> desc mysql.user;    //查看表结构，找到密码存放字段，5.0版本在authentication_string字段中
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Field                  | Type                              | Null | Key | Default               | Extra |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Host                   | char(60)                          | NO   | PRI |                       |       |
| User                   | char(32)                          | NO   | PRI |                       |       |
| Select_priv            | enum('N','Y')                     | NO   |     | N                     |       |
| Insert_priv            | enum('N','Y')                     | NO   |     | N                     |       |
| Update_priv            | enum('N','Y')                     | NO   |     | N                     |       |
| Delete_priv            | enum('N','Y')                     | NO   |     | N                     |       |
| Create_priv            | enum('N','Y')                     | NO   |     | N                     |       |
| Drop_priv              | enum('N','Y')                     | NO   |     | N                     |       |
| Reload_priv            | enum('N','Y')                     | NO   |     | N                     |       |
| Shutdown_priv          | enum('N','Y')                     | NO   |     | N                     |       |
| Process_priv           | enum('N','Y')                     | NO   |     | N                     |       |
| File_priv              | enum('N','Y')                     | NO   |     | N                     |       |
| Grant_priv             | enum('N','Y')                     | NO   |     | N                     |       |
| References_priv        | enum('N','Y')                     | NO   |     | N                     |       |
| Index_priv             | enum('N','Y')                     | NO   |     | N                     |       |
| Alter_priv             | enum('N','Y')                     | NO   |     | N                     |       |
| Show_db_priv           | enum('N','Y')                     | NO   |     | N                     |       |
| Super_priv             | enum('N','Y')                     | NO   |     | N                     |       |
| Create_tmp_table_priv  | enum('N','Y')                     | NO   |     | N                     |       |
| Lock_tables_priv       | enum('N','Y')                     | NO   |     | N                     |       |
| Execute_priv           | enum('N','Y')                     | NO   |     | N                     |       |
| Repl_slave_priv        | enum('N','Y')                     | NO   |     | N                     |       |
| Repl_client_priv       | enum('N','Y')                     | NO   |     | N                     |       |
| Create_view_priv       | enum('N','Y')                     | NO   |     | N                     |       |
| Show_view_priv         | enum('N','Y')                     | NO   |     | N                     |       |
| Create_routine_priv    | enum('N','Y')                     | NO   |     | N                     |       |
| Alter_routine_priv     | enum('N','Y')                     | NO   |     | N                     |       |
| Create_user_priv       | enum('N','Y')                     | NO   |     | N                     |       |
| Event_priv             | enum('N','Y')                     | NO   |     | N                     |       |
| Trigger_priv           | enum('N','Y')                     | NO   |     | N                     |       |
| Create_tablespace_priv | enum('N','Y')                     | NO   |     | N                     |       |
| ssl_type               | enum('','ANY','X509','SPECIFIED') | NO   |     |                       |       |
| ssl_cipher             | blob                              | NO   |     | NULL                  |       |
| x509_issuer            | blob                              | NO   |     | NULL                  |       |
| x509_subject           | blob                              | NO   |     | NULL                  |       |
| max_questions          | int(11) unsigned                  | NO   |     | 0                     |       |
| max_updates            | int(11) unsigned                  | NO   |     | 0                     |       |
| max_connections        | int(11) unsigned                  | NO   |     | 0                     |       |
| max_user_connections   | int(11) unsigned                  | NO   |     | 0                     |       |
| plugin                 | char(64)                          | NO   |     | mysql_native_password |       |
| authentication_string  | text                              | YES  |     | NULL                  |       |
| password_expired       | enum('N','Y')                     | NO   |     | N                     |       |
| password_last_changed  | timestamp                         | YES  |     | NULL                  |       |
| password_lifetime      | smallint(5) unsigned              | YES  |     | NULL                  |       |
| account_locked         | enum('N','Y')                     | NO   |     | N                     |       |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
45 rows in set (0.00 sec)
mysql> select host,user,authentication_string from mysql.user;  //查看host，user，authentication_string上字段的数据
+-----------+---------------+-------------------------------------------+
| host      | user          | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | root          | *6691484EA6B50DDDE1926A220DA01FA9E575C18A |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| %         | myadm         | *01A6717B58FF5C7EAFFF6CB7C96F7428EA65FE4C |
| localhost | myadm         | *01A6717B58FF5C7EAFFF6CB7C96F7428EA65FE4C |
| %         | bbs           | *6691484EA6B50DDDE1926A220DA01FA9E575C18A |
| localhost | bbs           | *6691484EA6B50DDDE1926A220DA01FA9E575C18A |
| localhost | ltp_admin     | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+-----------+---------------+-------------------------------------------+
8 rows in set (0.00 sec)
mysql> select host,user,authentication_string from mysql.user where user='root' and host='localhost';  //精准过滤出root用户的密码字段
+-----------+------+-------------------------------------------+
| host      | user | authentication_string                     |
+-----------+------+-------------------------------------------+
| localhost | root | *6691484EA6B50DDDE1926A220DA01FA9E575C18A |
+-----------+------+-------------------------------------------+
1 row in set (0.00 sec)
mysql> update mysql.user set authentication_string=null where user='root' and host='localhost';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select host,user,authentication_string from mysql.user where user='root' and host='localhost';
+-----------+------+-----------------------+
| host      | user | authentication_string |
+-----------+------+-----------------------+
| localhost | root | NULL                  |
+-----------+------+-----------------------+
1 row in set (0.00 sec)
mysql> \q
Bye
[root@localhost ~]# vi /etc/my.cnf   //修改配置
[mysqld]
……省略部分
# skip-grant-tables   //将这条免密登入注释掉
[root@localhost ~]# systemctl restart mysqld  //重启生效配置
[root@localhost ~]# mysql -uroot -p
Enter password: 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
[root@localhost ~]# mysql -uroot -p
Enter password:    //已经是空密码状态了，直接回车登入
Welcome to the MySQL monitor.  Commands end with ; or \g.
……省略部分

mysql> 

mysql> \q   //退出MySQL ，可以重新设置密码了
Bye
[root@localhost ~]# mysqladmin -u root -p password '123456'   //重新设置密码
Enter password: 
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.
[root@localhost ~]# mysql -uroot -p   //验证，使用新密码登入成功
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
……省略部分
mysql>