[root@oraserver139 ~]# mysql -uroot -p
Enter password:
ERROR 1045 (28000):Access denied for user 'root'@'localhost' (using password: NO)
查看当前安装的mysql版本：
root@oraserver139 ~]# rpm -qa | grep MySQL
MySQL-server-5.6.15-1.el6.x86_64
MySQL-client-5.6.15-1.el6.x86_64
MySQL-shared-compat-5.6.15-1.el6.x86_64
MySQL-devel-5.6.15-1.el6.x86_64
perl-DBD-MySQL-4.022-1.el6.rfx.x86_64
停止mysql服务：
[root@oraserver139 ~]# service mysql stop
Shutting down MySQL.. SUCCESS!
进入到skip-grant-tables模式：
[root@oraserver139 ~]#mysqld_safe --skip-grant-tables
140211 15:37:49 mysqld_safe Logging to '/var/lib/mysql/oraserver139.err'.
140211 15:37:49 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
现在就不需要密码就可以进入mysql了：
[root@oraserver139 ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.15 MySQL Community Server (GPL)
Copyright (c) 2000, 2013,Oracleand/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
进入mysql系统数据库：
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
修改root账户密码：
mysql>update user set password=password("12345") where user="root";
Query OK, 4 rows affected (0.02 sec)
Rows matched: 4 Changed: 4 Warnings: 0
刷新权限：
mysql>flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> exit
Bye
停止mysql进程：
[1]+ Stopped mysqld_safe --skip-grant-tables
启动mysql：
[root@oraserver139 ~]#service mysql start
Starting MySQL SUCCESS!
使用刚才修改的密码进入mysql：
[root@oraserver139 ~]#mysql -uroot -p12345