使用RedHat 系統線上安裝時提示This system is not registered with RHN.如下：

[[email protected] ~]# yum install httpd
Loaded plugins: rhnplugin, security
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
No package httpd available.
Nothing to do
解決方案：

1.解除安裝redhat自帶的yum元件

[[email protected] ~]# rpm -qa|grep yum|xargs rpm -e --nodeps

2.安裝CentOS的yum包 (新地址)

[[email protected] ~]#  wget  http://centos.ustc.edu.cn/centos/5/os/i386/CentOS/yum-metadata-parser-1.1.2-4.el5.i386.rpm
[[email protected] ~]# wget  http://centos.ustc.edu.cn/centos/5/os/i386/CentOS/yum-fastestmirror-1.1.16-21.el5.centos.noarch.rpm

3. 下載更新源，並存放在系統目錄中
[[email protected] ~]# wget http://www.linuxidc.com/files/2011/05/06/CentOS-Base.repo

[[email protected] ~]#mv CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo

4.生成快取並進行安裝

[[email protected] ~]# yum makecache
[[email protected] ~]# yum install xxx (你要裝的軟體名)

附言：對不起大家 我操作上述後還是失敗了，linux我不太熟悉. 又補充了下列操作後成功

解決辦法：

然後yum install git就能安裝了。