MySQL - How to operate if you forget your Root password

1. Enter the command

root@centos64 mysql]# /usr/bin/mysqld_safe --skip-grant-tables&

2 on the command line. Start a terminal and execute the following series of commands:

[root@centos64 proc]# mysql  
Welcome to the MySQL monitor.  Commands end with ; or \g.  
Your MySQL connection id is 1  
Server version: 5.6.13 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> UPDATE user SET password=password('admin') WHERE user='root';  
ERROR 1046 (3D000): No database selected  
mysql> show databases ;  
+--------------------+  
| Database           |  
+--------------------+  
| information_schema |  
| mysql              |  
| performance_schema |  
| test               |  
+--------------------+  
4 rows in set (0.06 sec)  
  
mysql> use mysql  
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  
mysql> UPDATE user SET password=password('admin') WHERE user='root';  
Query OK, 4 rows affected (0.04 sec)  
Rows matched: 4  Changed: 4  Warnings: 0  
  
mysql> flush privileges;   也可以不用。  
  
mysql> exit  
Bye

Note that it is possible that there is no user table at all. There is no root user.
If there is no such user, use:

mysql> insert into mysql.user(Host,User,Password,ssl_cipher,x509_issuer,x509_subject) values("localhost","root",password("admin"),"","","");  
Query OK, 1 row affected (0.10 sec)

3. Authorization. Give all permissions

mysql> grant all privileges on *.* to  'root'@'localhost' identified by 'admin' ;  
Query OK, 0 rows affected (0.06 sec)  
mysql> flush privileges;

and then start it in the normal way.

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