今天实战了下RedHat 5.6企业版，收费的呀
解决方法就是“用CentOS的yum更新源来实现RHEL5的YUM功能”
一、
下载CentOS5.6下的四个YUM文件，下载地址：
执行
rpm -ivh --nodeps yum-updatesd-0.9-2.el5.noarch.rpm
rpm -ivh --nodeps yum-fastestmirror-1.1.16-14.el5.centos.1.noarch.rpm
rpm -ivh --nodeps yum-metadata-parser-1.1.2-3.el5.centos.x86_64.rpm
rpm -ivh yum-3.2.22-33.el5.centos.noarch.rpm
二、
进入/etc/yum.erpos.d/，备份原有的redhat源列表配置文件
cd /etc/yum.repos.d/
mv rhel-debuginfo.repo rhel-debuginfo.repo.bak（这个其实我没备份）
下载CentOS-Base.repo，下载地址：
三、
用vi打开 CentOS-Base.repo.
将CentOS-Base.repo中所有的$releasever替换为5.6
一切OK拉，当然我还要继续装Orcale
附件；CentOS-Base.repo
#################################################################
# CentOS-Base.repo
#
# This file uses a new mirrorlist system developed by Lance Davis for CentOS.
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-5.6 - Base
baseurl=http://mirrors.ustc.edu.cn/centos/5.6/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-5.6 - Updates
baseurl=http://mirrors.ustc.edu.cn/centos/5.6/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5
#packages used/produced in the build but not released
[addons]
name=CentOS-5.6 - Addons
baseurl=http://mirrors.ustc.edu.cn/centos/5.6/addons/$basearch/
gpgcheck=1
gpgkey=http://mirrors.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5.6 - Extras
baseurl=http://mirrors.ustc.edu.cn/centos/5.6/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5.6 - Plus
baseurl=http://mirrors.ustc.edu.cn/centos/5.6/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.ustc.edu.cn/centos/RPM-GPG-KEY-CentOS-5
