redhat 安装时，没有进行注册，在用yum install *的时候会提示
由于redhat 没有注册，所有不能使用它自身的源进行更新，所以我们可以通过更换源来进行相关更新：
更改yum的源，即更换/etc/yum.repos.d/rhel-debuginfo.repo 这个文件。
将：
[base] name=CentOS-5-Base baseurl=http://centos.ustc.edu.cn/centos/5/os/$basearch/ gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #released updates [update] name=CentOS-5 - Updates baseurl=http://centos.ustc.edu.cn/centos/5/updates/$basearch/ gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #packages used/produced in the build but not released [addons] name=CentOS-5 - Addons baseurl=http://centos.ustc.edu.cn/centos/5/addons/$basearch/ gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #additional packages that may be useful [extras] name=CentOS-5 - Extras baseurl=http://centos.ustc.edu.cn/centos/5/extras/$basearch/ gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #additional packages that extend functionality of existing packages [centosplus] name=CentOS-5 - Plus baseurl=http://centos.ustc.edu.cn/centos/5/centosplus/$basearch/ gpgcheck=1 enabled=0 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #contrib - packages by Centos Users [contrib] name=CentOS-5 - Contrib baseurl=http://centos.ustc.edu.cn/centos/5/contrib/$basearch/ gpgcheck=1 enabled=0 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5 #packages in testing [testing] name=CentOS-5 - Testing baseurl=http://centos.ustc.edu.cn/centos/5/testing/$basearch/ gpgcheck=1 enabled=0 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
替换至/etc/yum.repos.d/rhel-debuginfo.repo 文件
