今天在用yum安装git的时候遇到这个问题，下面详细说下

#This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Setting up Install Process
Nothing to do

其实如果使用redhat的yum源需注册付费，费时费力，没有必要，所以我们只需要把自带的yum卸载然后再次安装即可

我的环境是redhat 6.4-x86_64的

第一步下载相关安装包

可以通过http://mirrors.163.com/centos下载，这是笔者已经下载好的http://pan.baidu.com/s/1qW0MbgC

第二步卸载Redhat自带的yum

#rpm -qa | grep yum | xargs rpm -e --nodeps

第三步安装下载的安装包

#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

第四步到http://mirrors.163.com的 centos帮助文档 
中下载CentOS6-Base-163.repo文件，存放到/etc/yum.repo.d中

#wget http://mirrors.163.com/.help/CentOS6-Base-163.repo

第五步将Centos6-Base-163.repo中的$releasever改为Centos的版本号即可

为了防止错误，也可使用我已修改好的文件http://pan.baidu.com/s/1o6AZ23o

文件修改成如下即可：

# 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

第六步 yum clean all 清除原有缓存

第七步 yum makecache  获取yum列表

等待，大约5分钟后出现下面提示，表示yum更改完成：

Metadata Cache Created

第八步 如果安装过程中还是出现某个包无法下载那么再次执行 yum clean all