进行yum本地源配置之前，需要在虚拟机设置中将本地光盘设置为已连接状态

1.挂载光盘

一旦关机仍需重新挂载（指令挂载）
su - root切换到管理员并切换到其家目录

[root@localhost ~]# mkdir /tmp/dvd
[root@localhost ~]# mount /dev/cdrom /tmp/dvd
mount: /dev/sr0 写保护，将以只读方式挂载
[root@localhost ~]# cd /tmp/dvd
[root@localhost dvd]# cd Packages
[root@localhost Packages]# cd /etc/yum.repos.d/
[root@localhost yum.repos.d]# ls
CentOS-Base.repo  CentOS-Debuginfo.repo  CentOS-Media.repo    CentOS-Vault.repo
CentOS-CR.repo    CentOS-fasttrack.repo  CentOS-Sources.repo  CentOS-x86_64-kernel.repo
[root@localhost yum.repos.d]# cat CentOS-Base.repo 
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#

[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#released updates 
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

2.备份源

[root@localhost Packages]# cd /etc/yum.repos.d/
[root@localhost ~]# cd /etc
[root@localhost etc]# cp -r yum.repos.d  yum.repos.d_copy
[root@localhost etc]# cd yum.repos.d
[root@localhost yum.repos.d]# rm -f *
[root@localhost yum.repos.d]# ls

3.配置本地软件源

[root@localhost yum.repos.d]# vim dvd.repo

下面是dvd.repo内容：
[dvd]
name=dvd
baseurl=file:///tmp/dvd
gpgcheck=0
按下i进入插入模式，ESC退出插入模式，:wq保存退出

4.yum list

[root@localhost yum.repos.d]# yum list

5.yum install gcc- c++

[root@localhost yum.repos.d]# yum install gcc-c++
已加载插件：fastestmirror, langpacks
Loading mirror speeds from cached hostfile
软件包 gcc-c++-4.8.5-44.el7.x86_64 已安装并且是最新版本
无须任何处理

如果是备份过目录之后又重新做了一遍，可能会出现Cannot find a valid baseurl for repo: dvd这种问题，可以参考一下下面的文章请点这里