ISOs are best downloaded from the Internet, for example:

 

•Red Hat Enterprise Linux (you must have a valid subscription to access the Red Hat Network)

•https://rhn.redhat.com/rhn/software/downloads/SupportedISOs.do

•Fedora

•http://mirrors.kernel.org/fedora/releases/18/Fedora/x86_64/iso/Fedora-18-x86_64-DVD.iso

•CentOS

•http://mirrors.kernel.org/centos/6.5/isos/x86_64/CentOS-6.5-x86_64-bin-DVD1.iso (DVD-2of2 is not needed)

 

If you have the Operating System on a DVD or CD-ROM, extract your ISO from the physical media.