sudo passwd
系统提示输入密码，即安装时的用户密码，然后，系统提示输入两次新密码
su
提示输入密码，输入密码后就切换到了root

转载自百度百科

1、进入CMD，执行set ORACLE_SID=ORCL，确保连接到正确的SID；
2、命令窗口运行sqlplus “/as sysdba” 启动窗口之后显示如下信息

SQL*Plus: Release 11.1.0.7.0 - Production on 星期三 3月 6 17:17:53 2013
Copyright (c) 1982, 2008, Oracle. All rights reserved.

连接到:
Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>
3、停止服务 shutdown immediate
SQL> shutdown immediate
ORA-01109: 数据库未打开

在安装samba增加用户，并且使用smbpasswd生成密码的时候出现如下错误：
Failed to find entry for user test.
Failed to modify password entry for user test
说明是没有该用户，请使用 -a 参数
OPTIONS
-a
This option specifies that the username following should be added to the local smbpasswd file, with the new
password typed (type for the old password). This option is ignored if the username following
already exists in the smbpasswd file and it is treated like a regular change password command. Note that
the default passdb backends require the user to already exist in the system password file (usually
/etc/passwd), else the request to add the user will fail.
This option is only available when running smbpasswd as root.
解决方法：
加参数‘-a’：
# smbpasswd -a 用户即可

一、卸载jdk1.4
由于Redhat Enterprise Linux 5.6 中自带安装了jdk1.4.2的，所以在安装jdk1.6前我把jdk1.4.2的卸了，步骤如下：

打开终端输入 yum remove java
终端显示 Is this ok [y/N]:
输入y ，按回车。
终端显示 Complete! 此时jdk1.4已被卸了。

二、解压jdk1.7的安装包，配置环境变量
输入javac
报错：cannot restore segment prot after reloc: Permission denied
解决办法：这是因为SELINUX的问题，需要关闭SELINX，执行：/usr/sbin/setenforce 0
再次输入javac，已经成功安装