[root@localhost ~]# mount /dev/cdrom /media/cdrom/
mount: /dev/sr0 写保护，将以只读方式挂载

[root@localhost /]# cd /etc/yum.repos.d/
[root@localhost yum.repos.d]# mkdir bak　　　　#创建一个文件夹来存放多余的配置文件
[root@localhost yum.repos.d]# mv *.* bak/　　　　　　
[root@localhost yum.repos.d]# cd bak/
[root@localhost bak]# ls
CentOS-Base.repo  CentOS-Debuginfo.repo  CentOS-Media.repo    CentOS-Vault.repo
CentOS-CR.repo    CentOS-fasttrack.repo  CentOS-Sources.repo
[root@localhost bak]# mv CentOS-Media.repo ../
[root@localhost bak]# cd ../
[root@localhost yum.repos.d]# vi CentOS-Media.repo 

# CentOS-Media.repo
#
#  This repo can be used with mounted DVD media, verify the mount point for
#  CentOS-7.  You can use this repo and yum to install items directly off the
#  DVD ISO that we release.
#
# To use this repo, put in your DVD and use it with the other repos too:
#  yum --enablerepo=c7-media [command]
#
# or for ONLY the media repo, do this:
#
#  yum --disablerepo=\* --enablerepo=c7-media [command]

[c7-media]
name=CentOS-$releasever - Media
baseurl=file:///media/CentOS/
        file:///media/cdrom/　　#本地yum源所在路径
        file:///media/cdrecorder/
gpgcheck=0   #这里为0不进行检查
enabled=1　　　#这里为1　　启动
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

~                                                                  

[root@localhost /]# yum list