1．修改MySQL的登入設定：
vim /etc/my.cnf
在[mysqld]的段中加上一句：skip-grant-tables

2．重新啟動mysql
service mysql restart

3．登入並修改MySQL的root密碼

 mysql> use mysql; 
 Database changed 
 mysql> update user set password = password ('new-password') where user = 'root'; 
 Query OK, 0 rows affected (0.00 sec) 
 Rows matched: 5
 
 Changed: 0 Warnings: 0 
 mysql> flush privileges; 
 Query OK, 0 rows affected (0.01 sec) 
 mysql> quit

4．將MySQL的登入設定修改回來
vim /etc/my.cnf
將剛才在[mysqld]的段中加上的skip-grant-tables註釋
儲存並且退出vim

5．重新啟動mysql
service mysql restart