挂载镜像文件
mkdir /mnt/cdrom mount /dev/cdrom /mnt/cdrom
编辑repo文件
vim /etc/yum.repos.d/centos7-local.repo [local] name=local baseurl=file:///mnt/cdrom enabled=1 gpgcheck=1 gpgkey=file:///mnt/cdrom/RPM-GPG-KEY-CentOS-7