CentOS7安装初始默认没有任何yum 源，以挂载本地DVD到/mnt/cdrom，将系统yum源连接到/mnt/cdrom为例。

# 用yum-config-manager生成一个源文件模版
[root@server0 yum.repos.d]# yum-config-manager --add-repo=cdrom
Loaded plugins: langpacks, product-id
adding repo from: cdrom

[cdrom]
name=added from: cdrom
baseurl=cdrom
enabled=1

# 将生成的模版编辑如下
[root@server0 yum.repos.d]# cat cdrom.repo

[cdrom]
name=DVD Media
baseurl=file:///mnt/cdrom
enabled=1

# 挂载CDROM
[root@server0 yum.repos.d]# mount /dev/cdrom /mnt/cdrom/
mount: /dev/sr0 is write-protected, mounting read-only

# 导入RPM-GPG-KEY 
[root@server0 yum.repos.d]# rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-xxxx

# 查看
[root@server0 ~]# yum repolist
Loaded plugins: langpacks, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
repo id                                                           repo name                                                           status
cdrom                                                           DVD Media                                                         4,305
repolist: 4,305

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