1.确保RHEL5中已经安装了yum
[root@lvs-master ~]# rpm -qa |grep yum
yum-metadata-parser-1.1.2-3.el5
yum-updatesd-0.9-2.el5
yum-3.2.22-26.el5
yum-security-1.1.16-13.el5
yum-rhn-plugin-0.5.4-15.el5
# cd /etc/yum.repos.d/
#mv CentOS-Base.repo CentOS-Base.repo.bak
#wget http://docs.linuxtone.org/soft/lemp/CentOS-Base.repo
该文件内容如下：
[base]
name=CentOS-5 - Base
baseurl=http://centos.ustc.edu.cn/centos/5/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #released updates
[update]
name=CentOS-5 - Updates
baseurl=http://centos.ustc.edu.cn/centos/5/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #packages used/produced in the build but not released
[addons]
name=CentOS-5 - Addons
baseurl=http://centos.ustc.edu.cn/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5 - Extras
baseurl=http://centos.ustc.edu.cn/centos/5/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5 - Plus
baseurl=http://centos.ustc.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #contrib - packages by Centos Users
[contrib]
name=CentOS-5 - Contrib
baseurl=http://centos.ustc.edu.cn/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #packages in testing
[testing]
name=CentOS-5 - Testing
baseurl=http://centos.ustc.edu.cn/centos/5/testing/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
第六步 yum clean all 清除原有缓存
第七步 yum makecache 获取yum列表
等待，大约三分钟后出现下面提示，表示yum更改完成：
Metadata Cache Created