RHEL 5 , 用安装CD作为YUM的Repository

官方文档写的非常好

14.5. Upgrading the System Off-line with ISO and Yum

Create a target directory to mount your ISO image. This directory is not automatically created when mounting, so create it before proceeding to the next step, as root, type:
```
mkdir mount_dir
```
Replace mount_dir with a path to the mount directory. Typicaly, users create it as a subdirectory in the /media/ directory.
Mount the Red Hat Enterprise Linux 5 installation ISO image to the previously created target directory. As root, type:
```
mount -o loop iso_name mount_dir
```
Replace iso_name with a path to your ISO image and mount_dir with a path to the target directory. Here, the -o loop option is required to mount the file as a block device.
Check the numeric value found on the first line of the .discinfo file from the mount directory:
```
head -n1 mount_dir/.discinfo
```
The output of this command is an identification number of the ISO image, you need to know it to perform the following step.
Create a new file in the /etc/yum.repos.d/ directory, named for instance new.repo, and add a content in the following form. Note that configuration files in this directory must have the .repo extension to function properly.
```
[repository] 
mediaid=media_id 
name=repository_name
baseurl=repository_url
gpgkey=gpg_key 
enabled=1 
gpgcheck=1
```
Replace media_id with the numeric value found in mount_dir/.discinfo. Set the repository name instead ofrepository_name, replace repository_url with a path to a repository directory in the mount point and gpg_key with a path to the GPG key.

For example, the repository settings for Red Hat Enterprise Linux 5 Server ISO can look as follows:
```
[rhel5-Server] 
mediaid=1354216429.587870 
name=RHEL5-Server
baseurl=file:///media/rhel5/Server 
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release 
enabled=1 
gpgcheck=1
```
Update all yum repositories including /etc/yum.repos.d/new.repo created in previous steps. As root, type:
```
yum update
```

RHEL 7