1.打开
/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
...
2.重启mysql
# /etc/init.d/mysqld restart
Stopping MySQL: [ OK ]
Starting MySQL: [ OK ]
3．登录并修改MySQL的root密码
输入 /usr/bin/mysql
出现：
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.
输入 USE mysql ;
出现：
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
输入：
UPDATE user SET Password = password ( '123456' ) WHERE User = 'root' ; 这里修改密码为 123456；
出现：
Query OK, 0 rows affected (0.00 sec)
Rows matched: 2 Changed: 0 Warnings: 0
输入：flush privileges ;
Query OK, 0 rows affected (0.01 sec)
输入： 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 ]