默认情况下安装完成后mysql没设root密码，可以直接登录：
[root@centos6 ~]# mysql -uroot
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 5.1.49 MySQL Community Server (GPL)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
mysql>
可以使用mysqladmin工具的password选项给root用户添加密码：
[root@centos6 ~]# mysqladmin -uroot password ‘654321‘
设置密码后，不输入密码将登陆失败：
[root@centos6 ~]# mysql -uroot
ERROR 1045 (28000): Access denied for user ‘root‘@‘localhost‘ (using password: NO)
[root@centos6 ~]# mysql -uroot -p654321
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 5.1.49 MySQL Community Server (GPL)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
mysql>
重置root密码需要编辑配置文件，加入一条语句：skip-grant：
[root@centos6 ~]# vim /etc/my.cnf
……
read_rnd_buffer_size = 4M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size= 16M
# Try number of CPU‘s*2 for thread_concurrency
thread_concurrency = 8
skip-grant
……
重启MySQL
[root@centos6 ~]# mysqld restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!
此时不需要密码即可登录
[root@centos6 ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.1.49 MySQL Community Server (GPL)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
mysql>
使用mysql库
mysql> use mysql
Database changed
更改user表中root的密码为aming.com
mysql> update user set password=password(‘123456‘) where user=‘root‘;
Query OK, 3 rows affected (0.01 sec)
Rows matched: 3 Changed: 3 Warnings: 0
查看user表中root的信息，\G看起来整洁：
mysql> select * from user where user=‘root‘ \G;
*************************** 1. row ***************************
Host: localhost
User: root
Password: *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9
Select_priv: Y
Insert_priv: Y
Update_priv: Y
Delete_priv: Y
Create_priv: Y
Drop_priv: Y
Reload_priv: Y
Shutdown_priv: Y
Process_priv: Y
File_priv: Y
Grant_priv: Y
References_priv: Y
Index_priv: Y
Alter_priv: Y
Show_db_priv: Y
Super_priv: Y
Create_tmp_table_priv: Y
Lock_tables_priv: Y
Execute_priv: Y
Repl_slave_priv: Y
Repl_client_priv: Y
Create_view_priv: Y
Show_view_priv: Y
Create_routine_priv: Y
Alter_routine_priv: Y
Create_user_priv: Y
Event_priv: Y
Trigger_priv: Y
ssl_type:
ssl_cipher:
x509_issuer:
x509_subject:
max_questions: 0
max_updates: 0
max_connections: 0
max_user_connections: 0
……
退出MySQL，编辑配置文件，删除skip-grant行，重启MySQL，再次登录即可使用新密码登录。
[root@centos6 ~]# vim /etc/my.cnf
[root@centos6 ~]# mysqld restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!
[root@centos6 ~]# mysql
ERROR 1045 (28000): Access denied for user ‘root‘@‘localhost‘ (using password: NO)
[root@centos6 ~]# mysql -uroot -p123456
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.1.49 MySQL Community Server (GPL)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
mysql>
原文地址：http://rachy.blog.51cto.com/11428504/1892329
