1.修改配置文件

vi /etc/my.cnf

在[mysqld]的段中加上一句

skip-grant-tables

2.保存重启 mysql

service mysqld restart

3.修改root密码

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 mysql.user set authentication_string=password(‘****‘) where user=‘root‘;
Query OK, 0 rows affected, 1 warning (0.00 sec)
Rows matched: 2 Changed: 0 Warnings: 1

mysql> exit

3.删除配置文件中的 skip-grant-tables

4.保存重启 mysql

service mysqld restart

5.登录 mysql,设置登录权限

mysql -u root -p

Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.15 MySQL Community Server (GPL)

Copyright (c) 2000, 2016, 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> GRANT ALL PRIVILEGES ON . TO ‘root‘@‘%‘ IDENTIFIED BY ‘ky123456KY+-)(‘ WITH GRANT OPTION;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mySql-5.7,root用户忘记密码处理方式

原文：http://blog.51cto.com/liuqh/2061241