由于RHEL的yum在线更新是收费的，如果没有注册的话是不能使用的，即不能在线安装软件。在这种情况下，如果我们使用的机器安装的是RHEL系统要是每次安装软件先挂载本地光盘会很繁琐，而且有些软件也是老版本的，这种情况下我们可以借助CentOS的YUM源来满足我们的需求。
一、删除RHEL原有的YUM
rpm-aq|grepyum|xargsrpm-e--nodeps
二、下载CentOS的yum安装包（163源）
wgethttp://mirrors.163.com/centos/5/os/x86_64/CentOS/yum-3.2.22-40.el5.centos.noarch.rpm
wgethttp://mirrors.163.com/centos/5/os/x86_64/CentOS/yum-fastestmirror-1.1.16-21.el5.centos.noarch.rpm
wgethttp://mirrors.163.com/centos/5/os/x86_64/CentOS/yum-metadata-parser-1.1.2-4.el5.x86_64.rpm
wgethttp://mirrors.163.com/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
三、安装CentOS的YUM安装包
yum和yum-plugin-fastestmirror需要一起安装，这两个包存在依赖关系，分开安装会失败，安装之前先把RPM-GPG-KEY导入系统，否则会出现警告信息
rpm-ivhyum-metadata-parser-1.1.2-4.el5.x86_64.rpm
rpm--importRPM-GPG-KEY-CentOS-5
rpm–ivhyum-3.2.22-40.el5.centos.noarch.rpmyum-fastestmirror-1.1.16-21.el5.centos.noarch.rm
至此我们就可以在线使用yum了
四、修改yum源
为了使用在线使用Yum安装软件更快，我们可以使用国内的网易Yum源或者其他国内yum源
五、更改yum源
#我们使用网易的CentOS镜像源
cd/etc/yum.repos.d/
virhel-debuginfo.repo
#CentOS-Base.repo
#
#ThemirrorsystemusestheconnectingIPaddressoftheclientandthe
#updatestatusofeachmirrortopickmirrorsthatareupdatedtoand
#geographicallyclosetotheclient.YoushouldusethisforCentOSupdates
#unlessyouaremanuallypickingothermirrors.
#
#Ifthemirrorlist=doesnotworkforyou,asafallbackyoucantrythe
#remarkedoutbaseurl=lineinstead.
#
#
[base]
name=CentOS-5-Base-163.com
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=os
baseurl=http://mirrors.163.com/centos/5/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#releasedupdates
[updates]
name=CentOS-5-Updates-163.com
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=updates
baseurl=http://mirrors.163.com/centos/5/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#packagesused/producedinthebuildbutnotreleased
[addons]
name=CentOS-5-Addons-163.com
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=addons
baseurl=http://mirrors.163.com/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#additionalpackagesthatmaybeuseful
[extras]
name=CentOS-5-Extras-163.com
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=extras
baseurl=http://mirrors.163.com/centos/5/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#additionalpackagesthatextendfunctionalityofexistingpackages
[centosplus]
name=CentOS-5-Plus-163.com
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=centosplus
baseurl=http://mirrors.163.com/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
#contrib-packagesbyCentosUsers
[contrib]
name=CentOS-5-Contrib-163.com
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=contrib
baseurl=http://mirrors.163.com/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
六、清理
yumcleanall
yummakecache
七、更新
yumupdate