1.檢查yum包 rpm -qa |grep yum

2.刪除自帶包
rpm -aq | grep yum | xargs rpm -e –nodeps

3.再檢查一下
rpm -qa |grep yum

4.下載更新包

wget http://mirrors.163.com/centos/6/os/x86_64/Packages/python-urlgrabber-3.9.1-11.el6.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-37.el6.noarch
 
.rpm
wget  http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-3.2.29-73.el6.centos.noarch.rpm
wget http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-updateonboot-1.1.30-37.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-utils-1.1.30-37.el6.noarch.rpm

5.執行安裝
rpm -ivh yum-*
注意：如果出現報錯不要慌，這個問題很噁心會導致後面安裝前功盡棄，使用下面語句更新rpm -Uvh python-urlgrabber版本，不更新肯定安裝不過去。
rpm -Uvh python-urlgrabber-3.9.1-11.el6.noarch.rpm

error: Failed dependencies:
        python-urlgrabber >= 3.9.1-10 is needed by yum-3.2.29
 
-73.el6.centos.noarch

重新執行：
rpm -ivh yum-*

warning: yum-3.2.29-73.el6.centos.noarch.rpm: Header V3 RSA/SHA1 Signature, key ID c105b9de: NOKEY
Preparing...                ########################################### [100%]
   1:yum-metadata-parser    ########################################### [ 20%]
   2:yum-plugin-fastestmirro########################################### [ 40%]
   3:yum                    ########################################### [ 60%]
   4:yum-updateonboot       ########################################### [ 80%]
   5:yum-utils              ########################################### [100%]

安裝成功了

6.切換源
cd /etc/yum.repos.d/
mv redhat.repo redhat.repo.bak
mv rhel-source.repo rhel-source.repo.bak
vi /etc/yum.repos.d/CentOS-Base.repo
貼上如下資訊：

#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
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=os
baseurl=http://mirrors.163.com/centos/7/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6

#released updates
[updates]
name=CentOS-6 - Updates - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=updates
baseurl=http://mirrors.163.com/centos/7/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6

#additional packages that may be useful
[extras]
name=CentOS-6 - Extras - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=extras
baseurl=http://mirrors.163.com/centos/7/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/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/7/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6

8.清理快取
yum clean all
yum makecache

9.驗證
yum install telnet