CentOS7更换yum源

• 备份原文件

  mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

• 下载阿里源文件替换

   curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

• 建立缓存

  yum makecache