提示報錯如下：
Loaded plugins: aliases, changelog, downloadonly, kabi, presto, product-id, refresh-packagekit, security, subscription-manager, tmprepo, verify,
: versionlock
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.

1 刪除redhat原有的yum

2 下載yum安裝文件
wget http://mirrors.163.com/centos/6.9/os/x86_64/Packages/yum-3.2.29-81.el6.centos.noarch.rpm

wget http://mirrors.163.com/centos/6.9/os/x86_64/Packages/yum-metadata-parser-1.1.2-16.el6.x86_64.rpm

wget http://mirrors.163.com/centos/6.9/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm

wget http://mirrors.163.com/centos/6.9/os/x86_64/Packages/python-iniparse-0.3.1-2.1.el6.noarch.rpm

wget http://mirrors.163.com/centos/6.9/os/x86_64/Packages/python-urlgrabber-3.9.1-11.el6.noarch.rpm

#cd /etc/yum.repos.d/
#rm -rf rhel-source.repo
wget http://mirrors.163.com/centos/6.9/os/x86_64/Packages/centos-release-6-9.el6.12.3.x86_64.rpm

3 進行安裝yum
rpm -e redhat-release-server-6Server-6.5.0.1.el6.x86_64 --nodeps
rpm -ivh centos-release-6-9.el6.12.3.x86_64.rpm

4 清除原有緩存
#yum clean all

5 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

This system is not registered to Red Hat