[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 　　#后面东西太多了。。。