YUM是RedHat Linux在线安装更新及软件的工具，但是这是RHEL5的收费功能，如果没有购买Redhat的服务时不能使用RHEL5的更新源的，会提示注册。
由于CentOS是从Redhat演化而来的免费Linux版本，因此可以利用CentOS的yum更新源来实现RHEL5的YUM功能。配置方法如下：
检查yum是否安装，默认情况下都是安装好的，总共4各包。
[root@linux-a ~]# rpm -qa |grep yum
yum-metadata-parser-1.0-8.fc6
yum-3.0.1-5.el5
yum-rhn-plugin-0.4.3-1.el5
yum-updatesd-3.0.1-5.el5
配置yum更新源
创建/etc/yum.repos.d/CentOS-Base.repo文件，定义yum更新源，这里使用的是上海交大的CentOS更新源
[root@linux-a ~]# vi /etc/yum.repos.d/CentOS-Base.repo
[base]
name=CentOS-5-Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever5&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
baseurl=http://ftp.sjtu.edu.cn/centos/5/os/$basearch/
gpgcheck=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#released updates
[update]
name=CentOS-5-Updates
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=updates
baseurl=http://ftp.sjtu.edu.cn/centos/5/updates/$basearch/
gpgcheck=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#packages used/produced in the build but not released
[addons]
name=CentOS-5-Addons
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=addons
baseurl=http://ftp.sjtu.edu.cn/centos/5/addons/$basearch/
gpgcheck=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that may be useful
[extras]
name=CentOS-5-Extras
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=extras
baseurl=http://ftp.sjtu.edu.cn/centos/5/extras/$basearch/
gpgcheck=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5-Plus
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=centosplus
baseurl=http://ftp.sjtu.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=0
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#contrib - packages by Centos Users
[contrib]
name=CentOS-5-Contrib
#mirrorlist=http://mirrorlist.centos.org/?release=4&arch=$basearch&repo=contrib
baseurl=http://ftp.sjtu.edu.cn/centos/5/contrib/$basearch/
gpgcheck=0
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
# vi dag.repo
[dag]
name=Dag RPM Repository for RHEL5
baseurl=http://ftp.riken.jp/Linux/dag/redhat/el5/en/$basearch/dag/
enabled=1
gpgcheck=0
gpgkey=http://ftp.riken.jp/Linux/dag/packages/RPM-GPG-KEY.dag.txt
导入key
[root@linux-a ~]# rpm --import
运行YUM，测试
[root@linux-a ~]# yum install xmms-mp3
Loading "installonlyn" plugin
Loading "rhnplugin" plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Package xmms-mp3.i386 1:1.2.10-16.el5.rf set to be updated
--> Running transaction check
--> Processing Dependency: libglib-1.2.so.0 for package: xmms-mp3
--> Processing Dependency: libgdk-1.2.so.0 for package: xmms-mp3
--> Processing Dependency: libgthread-1.2.so.0 for package: xmms-mp3
--> Processing Dependency: libgmodule-1.2.so.0 for package: xmms-mp3
--> Processing Dependency: libgtk-1.2.so.0 for package: xmms-mp3
--> Processing Dependency: libxmms.so.1 for package: xmms-mp3
--> Restarting Dependency Resolution with new changes.
--> Populating transaction set with selected packages. Please wait.
---> Package xmms.i386 1:1.2.10-14.el5.rf set to be updated
---> Package glib.i386 1:1.2.10-20.el5 set to be updated
---> Downloading header for gtk+ to pack into transaction set.
gtk+-1.2.10-56.el5.i386.r 100% |=========================| 25 kB 00:00
---> Package gtk+.i386 1:1.2.10-56.el5 set to be updated
--> Running transaction check
--> Processing Dependency: libmikmod.so.2 for package: xmms
--> Processing Dependency: gdk-pixbuf >= 0.18.0 for package: gtk+
--> Restarting Dependency Resolution with new changes.
--> Populating transaction set with selected packages. Please wait.
---> Downloading header for gdk-pixbuf to pack into transaction set.
gdk-pixbuf-0.22.0-25.el5. 100% |=========================| 16 kB 00:00
---> Package gdk-pixbuf.i386 1:0.22.0-25.el5 set to be updated
---> Downloading header for mikmod to pack into transaction set.
mikmod-3.1.6-38.1.i386.rp 100% |=========================| 7.7 kB 00:00
---> Package mikmod.i386 0:3.1.6-38.1 set to be updated
--> Running transaction check
Dependencies Resolved