使用redhat6.0 系统在线安装时提示This system is not registered with RHN.如下：
[root@localhost ~]# yum install gcc
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：
1.卸载redhat自带的yum组件
[root@localhost ~]# rpm -qa|grep yum|xargs rpm -e --nodeps
2.安装centos的yum包
# wget http://mirror.centos.org/centos/6/os/i386/Packages/python-iniparse-0.3.1-2.1.el6.noarch.rpm
# wget http://mirror.centos.org/centos/6/os/i386/Packages/yum-metadata-parser-1.1.2-16.el6.i686.rpm
# wget http://mirror.centos.org/centos/6/os/i386/Packages/yum-3.2.29-40.el6.centos.noarch.rpm
# wget http://mirror.centos.org/centos/6/os/i386/Packages/yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm
#rpm -ivh python-iniparse-0.3.1-2.1.el6.noarch.rpm
#rpm -ivh yum-metadata-parser-1.1.2-16.el6.i686.rpm
#rpm -ivh yum-3.2.29-40.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm
注意最后两个包必需同时安装，否则会相互依赖
3. 下载更新源，并存放在系统目录中
[root@localhost ~]# wget http://docs.linuxtone.org/soft/lemp/CentOS-Base.repo
[root@localhost ~]#mv CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo
4.生成缓存并进行安装
[root@localhost ~]# yum makecache
至此可以使用yum了。
补充更改yum源方法：
#我们使用网易的CentOS镜像源
# cd /etc/yum.repos.d/
# wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
# vi CentOS6-Base-163.repo
编辑文件，把文件里面的$releasever全部替换为版本号，即6 最后保存！或者直接把下面的内存拷贝到CentOS6-Base-163.repo文件中即可（已经修改好）
#########################################################################
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-6 - Base - 163.com
baseurl=http://mirrors.163.com/centos/6/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=os
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#released updates
[updates]
name=CentOS-6 - Updates - 163.com
baseurl=http://mirrors.163.com/centos/6/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#additional packages that may be useful
[extras]
name=CentOS-6 - Extras - 163.com
baseurl=http://mirrors.163.com/centos/6/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/6/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#contrib - packages by Centos Users
[contrib]
name=CentOS-6 - Contrib - 163.com
baseurl=http://mirrors.163.com/centos/6/contrib/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#########################################################################
清理yum缓存
# yum clean all
# yum makecache #将服务器上的软件包信息缓存到本地,以提高搜索安装软件的速度
# yum install vim* #测试域名是否可用