新安裝了redhat6.5安裝后，登錄系統，使用yum update 更新系統。提示：
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
無法更新。
redhat 默認自帶的 yum 源需要注冊，才能更新。我們想不花錢也可以更新，需要替換掉redhat的yum源。
1.檢查是否安裝yum包
查看RHEL是否安裝了yum，若是安裝了，那么又有哪些yum包：
[root@localhost ~]# rpm -qa |grep yum yum-metadata-parser-1.0-8.fc6 yum-3.0.1-5.el5 yum-rhn-plugin-0.4.3-1.el5 yum-updatesd-3.0.1-5.el
2 刪除redhat自帶的yum包
卸載上面顯示的所有yum包：
[root@localhost ~]# rpm -qa|grep yum|xargs rpm -e --nodeps（不檢查依賴，直接刪除rpm包）
再用
[root@localhost ~]# rpm -qa |grep yum
[root@localhost ~]#
查看，無信息顯示表示已經卸載完成。
3.下載新的yum包。使用Centos6.5的yum包
# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-metadata-parser-1.1.2-16.el6.i686.rpm
# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-3.2.29-40.el6.centos.noarch.rpm
# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm
安裝yum軟件包
注意:單個的安裝包可能會依賴其它包（例如yum和yum-fastestmirror會相互依賴），所以我們可以把所有這些包放在一起，用一行命令將它們同時安裝即可：
rpm -ivh yum-metadata-parser-1.1.2-16.el6.i686.rpm yum-3.2.29-40.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm
4.更換yum源。使用163的源
# cd /etc/yum.repos.d/ # wget http://mirrors.163.com/.help/CentOS6-Base-163.repo # vi CentOS6-Base-163.repo
編輯文件，把文件里面的$releasever全部替換為版本號，即6.5（:1,$s/$releasever/6.5然后按enter建) 最后保存！或者直接把下面的內存拷貝到CentOS6-Base-163.repo文件中即可（已經修改好）
# CentOS-Base.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. # # If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead. # # [base] name=CentOS-6.5 - Base - 163.com baseurl=http://mirrors.163.com/centos/6.5/os/$basearch/ #mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=os gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6 #released updates [updates] name=CentOS-6.5 - Updates - 163.com baseurl=http://mirrors.163.com/centos/6.5/updates/$basearch/ #mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=updates gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6 #additional packages that may be useful [extras] name=CentOS-6.5 - Extras - 163.com baseurl=http://mirrors.163.com/centos/6.5/extras/$basearch/ #mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=extras gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6 #additional packages that extend functionality of existing packages [centosplus] name=CentOS-6.5 - Plus - 163.com baseurl=http://mirrors.163.com/centos/6.5/centosplus/$basearch/ #mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=centosplus gpgcheck=1 enabled=0 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6 #contrib - packages by Centos Users [contrib] name=CentOS-6.5 - Contrib - 163.com baseurl=http://mirrors.163.com/centos/6.5/contrib/$basearch/ #mirrorlist=http://mirrorlist.centos.org/?release=6.5&arch=$basearch&repo=contrib gpgcheck=1 enabled=0 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
5.清除原有緩存
yum clean all
重建緩存，以提高搜索安裝軟件的速度
yum makecache
6.更新系統
# yum update
轉自：http://qingwang.blog.51cto.com/505009/1551228