Introduction
Yum(Yellow dog Updater, Modified) is an automatic updater and package installer/remover for rpm systems. It automatically computes dependencies and figures out what things should occur to install packages. It makes it easier to maintain groups of machines without having to manually update each one using rpm.More information can be refers to the website http://yum.baseurl.org/
Configuration on the Redhat OS
1.Plugged in the OS Image DVD to the SUT ODD
2.Umount the OS image from the directory /dev/sr0
[root@daimon ~]# umount /dev/sr0
3.Mount the OS image to the directory /dev/sr0 /mnt
[root@daimon ~]# mount /dev/sr0 /mnt/
4.Create a file to save the yum url & import the redhat dependent package
[root@daimon ~]# vim /etc/yum.repos.d/dvd.repo
[testyum]
name=dvd
baseurl=file:///mnt
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gdp/RPM-GPG-KEY-redhat-release
5.Test yum
[root@daimon ~]# yum -y install dovecot
6.check the install result
[root@daimon ~]# rpm -qa dovecot
7.delete the package
[root@daimon ~]# yum -y remove dovecot
原文：http://www.cnblogs.com/yongdaiblog-201409/p/6682339.html