If there's one thing all Linux users have in common, it's installing distros from ISO images. Whether your favorite distro's digital DNA evolved from the Debian, Slackware, Gentoo, or Red Hat families. Or whether you got the ISO from a download, a purchased CD/DVD/USB, or packaged with a book or magazine. The distro you installed on your hard drive came to you in the form of an ISO image.
A Live CD/DVD image has all the files, the file system, and the metadata your hard drive needs to run Linux in some specific software configuration from a CD/DVD, without installing it to your hard drive. A Live CD/DVD is often also an installable image, containing files and instructions that lead you through the process of installing Linux to your hard drive. Clearly, in the Linux world the expression “Image is everything" has a very different meaning than it does on the public scene.
A good example of just how “Everything" an image can be is best illustrated by Klaus Knopper's KNOPPIX distribution. On a single CD of 700MB capacity he has compressed an image that originally consisted of some 2GB of data. Using on-the-fly decompression, that one CD boots a full-scale Linux desktop system with a rich variety of applications including (if you have the graphics to handle it) all the spectacular bells and whistles of Compiz, which adds cool special effects to your Linux desktop.
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