我的电脑平台是dell的d620，安装了rehhat5 client 和windows xp双系统。
但是感觉rhel 5 使用本地源更新设置比较繁琐，而且不能更新到最新的包。
在网上搜到了一篇相关的帖子，便按照指导安装并成功。记录下安装过程。
以便备用。
1.配置yum
先把RHEL5自带的yum包删除，rpm -qa | grep yum，出来4个包，全部rpm -e 掉，还有一个RedHat-release，这个要—nodeps。然后从CentOS.ermly.com/centos/5.1/os/下载CentOS的4个与yum有关的包及centos-release-5-0.0安装。安装后的包如下
yum-metadata-parser-1.0-8.fc6
yum-3.0.5-1.el5.centos.5
yum-updatesd-3.0.5-1.el5.centos.5
修改yum的配置文件，vi /etc/yum.repos.d/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-5.1 - Base
baseurl=http://mirror.tini4u.net/centos/5.1/os/$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
gpgcheck=1
gpgkey=http://centos.ermly.com/centos/5.1/os/i386/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-5.1 - Updates
baseurl=http://mirror.tini4u.net/centos/5.1/os/$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
gpgcheck=1
gpgkey=http://centos.ermly.com/centos/5.1/os/i386/RPM-GPG-KEY-CentOS-5
#packages used/produced in the build but not released
[addons]
name=CentOS-5.1 - Addons
baseurl=http://mirror.tini4u.net/centos/5.1/os/$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
gpgcheck=1
gpgkey=http://centos.ermly.com/centos/5.1/os/i386/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5.1 - Extras
baseurl=http://mirror.tini4u.net/centos/5.1/os/$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
gpgcheck=1
gpgkey=http://centos.ermly.com/centos/5.1/os/i386/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5.1 – Plus
baseurl=http://mirror.tini4u.net/centos/5.1/os/$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
gpgcheck=1
enabled=0
gpgkey=http://centos.ermly.com/centos/5.1/os/i386/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-5.1 - Contrib
baseurl=http://mirror.tini4u.net/centos/5.1/os/$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
$basearch/
gpgcheck=1
enabled=0
gpgkey=http://centos.ermly.com/centos/5.1/os/i386/RPM-GPG-KEY-CentOS-5
为了保证源的可用性，我添加了多个国内的centos源。
导入rpm包的GPG密钥
rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY*
3. Update
在终端下面执行yum -y update。遇到网速不好，重试几次，可以完全下载，共有538M之多。此时提示与redhat-logos冲突，继续rpm -e -nodeps redhat-logos，再次yum -y update，这时Updating, CleanUp, Complete!
4.修复gdm登录界面
重启后已经可以看到RHEL5改头换面成CentOS了，但是到gdm登录界面时提示出错，意为找不到gdm的相关主题。没关系，可以登录，只不过界面难看一点。进入Gnome桌面后，登录下载一个自己喜欢的gdm logo theme. 在终端输入gdmsetup，把刚才下载的tar.gz拖到对话框中安装，再把默认的Redhat删除就OKay了！
5.加快你的yum的速度.
使用yum的扩展插件yum-fastestmirror，个人认为这个插件非常有效，速度真的是明显提高， #yum -y install yum-fastestmirror
注意，在Centos 4上,名字叫yum-plugin-fastestmirror
6.扩展你的rpm包
好多包官方没有,怎么搞定他.要我自己编译吗?
好了，你安装这个包,这个是redhat5的哦。你可以自己到
#B
这来找
rpm -Uhv
技巧3:rpm查找.