1、查看当前Linux操作系统RedHat 版本号与32/64位操作系统。
[root@localhost CentOS5]# more /etc/redhat-release
Red Hat Enterprise Linux Server release 5.8 (Tikanga)
[root@localhost centos5]# uname -a
Linux localhost.localdomain 2.6.18-308.el5 #1 SMP Fri Jan 27 17:17:51 EST 2012 x86_64 x86_64 x86_64 GNU/Linux
2、删除RedHat自带的yum服务
[root@localhost centos5]# rpm -qa|grep yum |xargs rpm -e --nodeps
3、下载相应的yum 安装包并安装（安装包个数因操作系统版本号不同会有存在差异）
[root@localhost centos5]# wget
[root@localhost centos5]# wget
[root@localhost centos5]# wget
[root@localhost centos5]# rpm -ivh yum*.rpm
4、配置yum源(推荐使用的是163的镜像)
[root@localhost centos5]# vi /etc/yum.repos.d/CenOS-Base.repo
添加以下内容：
# CentOS-Base.repo
#
# 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-$releasever - Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://mirrors.163.com/centos/5/os/x86_64/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-$releasever - Updates
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://mirrors.163.com/centos/5/updates/x86_64/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
baseurl=http://mirrors.163.com/centos/5/extras/x86_64/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
baseurl=http://mirrors.163.com/centos/5/centosplus/x86_64/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.163.com/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
baseurl=http://mirrors.163.com/centos/5/contrib/x86_64/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.163.com/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
5、清除缓存并下载新的镜像缓存
[root@localhost centos5]# yum clean all
[root@localhost centos5]# yum makecache
6、测试（查看当前subversion版本与检查服务器subversion版本）
[root@localhost yum.repos.d]# rpm -qa|grep subversion
subversion-1.6.11-7.el5_6.4
subversion-1.6.11-7.el5_6.4 [root@localhost yum.repos.d]# yum check-update subversion
Loaded plugins: fastestmirror, katello, product-id, subscription-manager
Updating certificate-based repositories.
Unable to read consumer identity
Loading mirror speeds from cached hostfile
subversion.i386 1.6.11-12.el5_10 base
subversion.x86_64 1.6.11-12.el5_10 base
Obsoleting Packages
centos-release.x86_64 10:5-11.el5.centos base
redhat-release.x86_64 5Server-5.8.0.3 installed
firefox.i386 31.3.0-4.el5.centos updates
firefox.i386 3.6.26-1.el5_7 installed
firefox.x86_64 31.3.0-4.el5.centos updates
firefox.x86_64 3.6.26-1.el5_7 installed
7、安装yum注意问题
根据Linux 的版本号安装相应的CentOS并引用CentOS版本号对应的CenOS-Base.repo文件,
（1）、如果安装了CentOS 5的yun，却引用CentOS6的源yum makecache时就会报错。
（2）、如果操作系统是RedHat 5，却安装 CentOS6 yum会导致安装时需要手动安装与升级大量的依赖包。
8、附：CentOS中国镜像网址