第一步：(停掉正在运行的mysql)
[root@maomao ~]# service mysqld stop
Stopping MySQL: [ OK ]
第二步：使用 “--skip-grant-tables”参数重新启动mysql
[root@mcy400 ~]# mysqld_safe --skip-grant-tables
[root@cy400 ~]# Starting mysqld daemon with databases from /var/lib/mysql
第三步：用帐号登录mysql
[root@cy400 ~]# mysql -u root
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.0.77 Source distribution
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
第四步：改变用户数据库
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
第五步：修改密码，下面()内的root123为新密码
mysql> update user set password=password('root123') where user='root';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3 Changed: 3 Warnings: 0
第六步：刷新权限表
mysql> flush previleges;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'previleges' at line 1
第七步：退出mysql
mysql> quit
Bye
第八步：对mysql进行重启
[root@cy400 ~]# service mysqld restart;
Stopping MySQL: [ OK ]
Starting MySQL: [ OK ]
第九步：用更改过的密码重新登录即可。
[root@cy400 ~]# mysql -u root -p
Enter password: admin123
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.0.77 Source distribution
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> quit
Bye
[root@cy400 ~]#
加入如下自动启动命令 /etc/rc.d/init.d/mysqld start