red hat linux使用yum 出现Loaded plugins: rhnplugin, security

使用RedHat 系统在线安装时提示This system is not registered with RHN.如下：

[root@localhost ~]# 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
解决方案：

下载更新源，并存放在系统目录中
[root@localhost ~]# wget http://www.linuxidc.com/files/2011/05/06/CentOS-Base.repo

[root@localhost ~]#mv CentOS_Base.repo /etc/yum.repos.d/CentOS-Base.repo

生成缓存并进行安装

[root@localhost ~]# yum makecache