第一步：备份你的原镜像文件，以免出错后可以恢复。mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup第二步：下载新的CentOS-Base.repo 到/etc/yum.repos.d/CentOS 5wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repoCentOS 6wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repoCentOS 7wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo第三步：运行yum makecache生成缓存yum clean allyum makecache