由于redhat6自带的yum要注册才能用，所以用centos的免费yum来替换redhat的收费yum。
环境：redhat6.8
具体步骤：
1.删除redhat6自带的yum
rpm -aq|grep yum|xargs rpm -e –nodeps
2.安装yum软件包
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-3.2.29-40.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm   //这两个文件要一起安装，因为这两个文件相互依赖
相关文件下载：
//centos镜像源
//163镜像源
3.备份原来的yum源配置文件
mv /etc/yum.repos.d/rhel-source.repo /etc/yum.repos.d/rhel-source.repo.bak
4.更改yum源（使用网易163的centos镜像源）
cd /etc/yum.repos.d
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
5.修改CentOS6-Base-163.repo文件
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
#########################################################################

6.清理yum缓存，重建缓存
yum clean al
yum makecache
7.测试yum
yum -y install vim
[root@redhat6 ~]# yum -y install vim
Loaded plugins: fastestmirror, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Loading mirror speeds from cached hostfile
Setting up Install Process
Package 2:vim-enhanced-7.4.629-5.el6_8.1.x86_64 already installed and latest version
Nothing to do
//vim我已经更新过一次了，所以nothing to do，但是前几行的信息不知道是什么情况，以前替换yum没出现这些东西，不过好像没影响。
yum替换成功！