1.修改

# vi /etc/my.cnf 
在[mysqld]的段中加上一句：skip-grant-tables 
例如： 
[mysqld] 
datadir=/var/lib/mysql 
socket=/var/lib/mysql/mysql.sock 
skip-grant-tables 
保存并且退出vi。 

2．重新启动mysqld 

# /etc/init.d/mysqld restart 
Stopping MySQL: [ OK ] 
Starting MySQL: [ OK ] 

3．登录并修改MySQL的root密码 

# /usr/bin/mysql 
Welcome to the MySQL monitor. Commands end with ; or \g. 
Your MySQL connection id is 3 to server version: 3.23.56 
Type 'help;' or '\h' for help. Type '\c' to clear the buffer. 
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 ( 'new-password' ) WHERE User = 'root' ; 
Query OK, 0 rows affected (0.00 sec) 
Rows matched: 2 Changed: 0 Warnings: 0 
mysql> flush privileges ; 
Query OK, 0 rows affected (0.01 sec) 
mysql> quit 
Bye 

4．将MySQL的登录设置修改回来 

# vi /etc/my.cnf 
将刚才在[mysqld]的段中加上的skip-grant-tables删除 
保存并且退出vi。 

5．重新启动mysqld 

# /etc/init.d/mysqld restart 
Stopping MySQL: [ OK ] 
Starting MySQL: [ OK ]