rhel5 使用centos 源更新

先将RHEL5自带的yum删除，执行

rpm -qa|grep yum

将所有找到的包都删除（有些需要加上--nodeps）

wget http://mirrors.163.com/centos/5.7/os/i386/CentOS/yum-3.2.22-37.el5.centos.noarch.rpm
wget http://mirrors.163.com/centos/5.7/os/i386/CentOS/yum-metadata-parser-1.1.2-3.el5.centos.i386.rpm
wget http://mirrors.163.com/centos/5.7/os/i386/CentOS/yum-fastestmirror-1.1.16-16.el5.centos.noarch.rpm
rpm –ivh yum-*

下载 http://mirrors.163.com/.help/CentOS5-Base-163.repo
用文本编辑打开，替换所有的$releasever为5.7

cd /etc/yum.repos.d/

vi CentOS-Base.repo #拷贝入修改过的repo内容

yum update

yum makecache

done！