由於Redhat的yum在線更新是收費的，如果沒有注冊的話是不能使用的，即不能在線安裝軟件。所以yum install 命令每次都安裝失敗
下面介紹一種更改yum源的方式：
系統說明：
系統：Red Hat Enterprise Linux Server 6.3
內核：Linux 2.6.32-279.el6.x86_64
1、刪除RHEL原有的yum
rpm -aq|grep yum|xargs rpm -e --nodeps #刪除
2、下載新的yum安裝包 #這里我們使用CentOS的yum源
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/python-iniparse-0.3.1-2.1.el6.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-metadata-parser-1.1.2-16.el6.x86_64.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-3.2.29-60.el6.centos.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-30.el6.noarch.rpm
(提示：如果下載時提示404找不到錯誤，請訪問http://mirrors.163.com/centos/6/os/x86_64/Packages/，手動查找上面四個包，有時候版本會有點小偏差)
3、安裝yum軟件包
rpm -ivh python-iniparse-0.3.1-2.1.el6.noarch.rpm
rpm -ivh yum-metadata-parser-1.1.2-16.el6.x86_64.rpm
rpm -ivh yum-3.2.29-60.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-30.el6.noarch.rpm
(這里要注意的是：最后兩個安裝包要放在一起同時安裝，否則會提示相互依賴，安裝失敗。)
4、更改yum源 #我們使用網易的CentOS鏡像源
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$releasever全部替換為版本號，即6 最后保存！
或者直接把下面的內存拷貝到CentOS6-Base-163.repo文件中即可
（已經修改好，不用下載直接新建CentOS6-Base-163.repo 也 可以）
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-6 - Base - 163.com
baseurl=http://mirrors.163.com/centos/6/os/$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
5、收尾，測試YUM 是否可用
yum clean all #清理yum緩存
yum makecache #將服務器上的軟件包信息緩存到本地,以提高搜索安裝軟件的速度
yum install vim* #測試yum是否可用