首先

[root@mode media]# cd /etc/yum.repos.d/
[root@mode yum.repos.d]# ll
total 16
-rw-r--r-- 1 root root  560 Dec 19 01:20 CentOS-Media.repo
drwxr-xr-x 2 root root 4096 Dec 18 20:03 bak
drwxr-xr-x 2 root root 4096 Jan 28 19:17 ncurses-devel
drwxr-xr-x 2 root root 4096 Mar 12 18:32 openssl-devel
[root@mode yum.repos.d]# cat CentOS-Media.repo 
# CentOS-Media.repo
#
# This repo is used to mount the default locations for a CDROM / DVD on
#  CentOS-5.  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=c5-media [command]
#  
# or for ONLY the media repo, do this:
#
#  yum --disablerepo=\* --enablerepo=c5-media [command]

[c5-media]
name=CentOS-$releasever - Media
baseurl=file:///mnt/cdrom/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5


看到CentOS-Media.repo中的 baseurl=file:///mnt/cdrom/了吗

假设指定了CentOS-meida源，系统会依据路径查找安装 所须要的包

然后创建文件夹文件，将镜像挂载到那个文件夹中

、

[root@mode yum.repos.d]# mkdir -p /mnt/cdrom
[root@mode yum.repos.d]# mount -o loop /dev/cdrom /mnt/cdrom

然后就能够安装须要安装的软件了：

[root@mode yum.repos.d]# yum --disablerepo=\* --enablerepo=c5-media install xinetd
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package xinetd.x86_64 2:2.3.14-16.el5 set to be updated
--> Finished Dependency Resolution

Dependencies Resolved

=======================================================================================================================================================================
 Package                              Arch                                 Version                                        Repository                              Size
=======================================================================================================================================================================
Installing:
 xinetd                               x86_64                               2:2.3.14-16.el5                                c5-media                               127 k

Transaction Summary
=======================================================================================================================================================================
Install       1 Package(s)
Upgrade       0 Package(s)

Total download size: 127 k
Is this ok [y/N]: y
Downloading Packages:
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing     : xinetd                                                                                                                                          1/1 

Installed:
  xinetd.x86_64 2:2.3.14-16.el5                                                                                                                                        

Complete!
[root@mode yum.repos.d]#