Centos系统mysql 忘记root用户的密码：
第一步：(停掉正在运行的mysql)
[root@maomao ~]# /etc/init.d/mysqld
stop
Stopping
MySQL:
[ OK ]
第二步：使用 “--skip-grant-tables”参数重新启动mysql
[root@mcy400 ~]# cd 到mysql目录，这里到bin目录，会提示“Please do a cd to the mysql installation directory and restart”
[root@mcy400 ~]# ./bin/mysqld_safe
--skip-grant-tables
[root@cy400 ~]# Starting mysqld daemon with
databases from /var/lib/mysql
注意：如果停在这一步的时候，请克隆一个新的会话接着下一步操作
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 privileges;
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 ~]# /etc/init.d/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
转载：http://blog.sina.com.cn/s/blog_4488002e0100z574.html
参考：http://blog.chinaunix.net/uid-25266990-id-2921603.html
