redhat預設自帶的yum源需要註冊付費才能更新，而centos的yum源是免費的，為了使用方便我們把red hat的yum源改成centos的網易的yum源。

1、解除安裝red hat的yum

rpm -qa|grep yum|xargs rpm -e --nodeps

2、下載centos的yum

64位
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-3.2.29-81.el6.centos.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-metadata-parser-1.1.2-16.el6.x86_64.rpm  
 

32位
wget http://mirrors.163.com/centos/6/os/i386/Packages/yum-3.2.29-81.el6.centos.noarch.rpm
wget http://mirrors.163.com/centos/6/os/i386/Packages/yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm 
wget http://mirrors.163.com/centos/6/os/i386/Packages/yum-metadata-parser-1.1.2-16.el6.i686.rpm

64位
rpm -ivh yum-metadata-parser-1.1.2-16.el6.x86_64.rpm yum-3.2.29-81.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm --force --nodeps

32位
rpm -ivh yum-metadata-parser-1.1.2-16.el6.i686.rpm yum-3.2.29-81.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm --force --nodeps
 

cd /etc/yum.repos.d/　　#進入到yum配置檔案目錄
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo　　#下載CentOS配置檔案
vi CentOS6-Base-163.repo　　#編輯配置檔案
:%s/$releasever/6/g          #把$releasever替換成現有系統的版本號(6)
yum clean all　　#清除yum快取
yum makecache　　#更新yum快取
yum update       #更新系統