备份目录/etc/yum.repos.d/下所有文件到其他目录
baseurl为网站内repodata文件夹所在路径
[epel]
name=epel
baseurl=https://mirrors.aliyun.com/epel/$releasever/$basearch
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
写入/etc/yum.repos.d/epel.repo
/dev/sr0 /misc/cd iso9660 defaults 0 0写入/etc/fstab实现光盘自动挂载
[c7-media]
name=CentOS-$releasever - Media
baseurl=file:///misc/cd/
gpgcheck=1
enabled=1
gpgkey=file:///misc/cd/RPM-GPG-KEY-CentOS-7
写入/etc/yum.repos.d/CentOS-Media.repo
