1.首先备份/etc/yum.repos.d/CentOS-Base.repo
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2.下载对应版本repo文件, 放入/etc/yum.repos.d/ 下 (操作前请做好相应备份)
3.运行以下命令生成缓存
yum clean all yum makecache