Once upon a time a guy named Klaus Knopper had an idea: why not create a version of Linux that boots from CD, and uses RAM for any files it needs, so that it doesn't have to touch the hard disk at all?
He did this, and called it KNOPPIX, and started an excellent trend.
It does take a good bit of memory, say 128 MB or better yet 256, so very old computers without much RAM won't work with Live CDs (as they collectively are called), but... most computers these days have more than enough RAM to use a Live CD. (You probably snickered at the anticlimax: 128 whole megabytes?)
What good are Live CDs? Here are a few uses:
- People with the misfortune of using Windows can learn what Linux is like.
- People who use Linux can learn what other distributions are like.
- Live CDs can have specialized software installed on them, e.g. dyne:bolic, which is designed to be a multimedia production system on a CD. It has a special version of the Linux kernel configured for the low latency that audio recording wants.
- A live CD will come right up, and can't be hacked...so you can make one that immediately starts up a web server with fixed content (Want to change it? Burn another CD and reboot...), that runs a venerable old computer as a router/firewall, or is dedicated to running retro video games using MAME.
- Live CDs have made advances; now they can put your home directory on a USB mass storage device, so that you can run Linux on a computer that you couldn't otherwise use without having to use Windows, and bring your environment with you with just a CD or DVD and a USB mass storage device.
Even people who use Windows under duress or, hard as it is to believe, by choice, can make use of Live CDs.
- Ever try to completely back up a Windows system? There are a few files that Windows keeps locked while it's running, so that a backup program can't read them. If you're not running Windows, those files are just files, and can be copied.
- Has something stopped working? While there are, sad to say, still devices whose manufacturers refuse to give out information needed to write a Linux driver and don't provide one themselves, Linux hardware detection has improved greatly. Boot a Live CD and try to use the device. If it works, you know the problem isn't with the device; it's with Windows or its configuration.
- Some Live CDs are packaged with programs for diagnosing errors, or repairing file systems, or detecting viruses and spyware. If your system is infested, then the easiest way to be in a trustworthy state is to not run anything on the hard disk.
Check out System Recovery with Knoppix for more info on how to repair a Linux system with a Knoppix Live CD. Here is an interview with the author of the book Knoppix Hacks on recovering Windows systems using Knoppix.
...OK. Perhaps this information will propagate to people who can use it.