Title: Using a Live Linux Distribution

I think it was in C Vu that I first heard about Knoppix, www.knoppix.org - a "live" Linux distribution that will run entirely from the CD, needing no installation or configuration. It is very good for demonstrating Linux, or for using a Linux desktop to sort something out on a computer that otherwise runs Windows. It can also be used to install Linux quickly; you get a Debian system that runs a mixture of testing and unstable packages, and you can do package management as you see fit. (A while ago I met someone who wanted a free entry-level CAD package, and it was quicker for me to install Linux and find a suitable package from www.debian.org than it would have been to look for an appropriate piece of Windows software.)

What is even more useful is a document called "Knoppix Remastering HOWTO", available at www.knoppix.net/docs/index.php/KnoppixRemasteringHowto - this explains how to copy Knoppix into a spare directory on your existing Linux hard drive, chroot into it and alter it as you see fit, and then create a new CD image of the altered version. This is useful for a number of reasons. Firstly, if you need to experiment with recent, less stable packages but you don't want to upgrade your existing stable Linux environment, you can safely mix both distributions using this method (although if you are doing chroot from a different distribution, make sure to use something like su - so as to set the environment variables correctly). Secondly, you can make customised bootable CDs whenever you want to (I turned the process into a script to make this easier, although the script is rather specific to my system so I'll leave that as an exercise).

On slower computers it can take a few hours to generate the CD image, but it is worth it. It means you are able to take your exact customised environment to anyone else's PC and run it there, so long as it is able to boot the CD (or the special floppy disk that you can write). You may have problems persuading certain laptops to do this, but most computers "out there" will be OK with it. An alternative is to use VNC to access your desktop remotely, but that needs a good Internet connection; customised CDs do not. There are all kinds of uses for this. If you're familiar with Linux then it will save a lot of time in comparison with messing around with everybody's Windows setups.

I experimented using re-writeable CDs rather than ordinary CDRs. Rewriteables are slower (both in writing and reading) and have reduced capacity, and they will only work if you can get your PC to boot off the CD recorder (they are not readable on ordinary CD-ROMs). However they do save on resources when you're testing, because they can be re-used.

If you are running on a machine with less than 256Mb of RAM then you almost certainly want to make a swap file to make things run faster. Swap files can be made on the hard disk on any FAT partition, and any existing Linux swap partitions will be used automatically. You can also save a persistent home directory on the hard disk. (When you're mastering the Knoppix CD, it's worth knowing that you shouldn't rely on anything being in the home directory on startup. If you need something to be there by default then you should arrange a boot-up script to put it there, but please make the script do a test first because the user might be running a persistent home directory on the hard drive and doesn't want it to be restored to the default each time.)

There are many other versions of Knoppix that other people have remastered. Gnoppix (www.gnoppix.org) is interesting because it is based on the stable Debian distribution, rather than testing/unstable, although I find that testing/unstable is fine in the context of bootable CDs because these systems have comparatively short uptimes and are used as desktop machines, not secure Internet servers. I tried Morphix (www.morphix.org) which is supposed to be easier to customise, but it does have its problems (in the current version at the time of writing, any extra packages you add are copied to RAM when the CD loads, which could cause problems if you want a lot of packages and RAM is limited) - it's probably better to invest time in remastering Knoppix yourself. Another interesting variant is Oralux (www.oralux.org) which is designed for blind people and takes you into an Emacs desktop with software speech synthesis (go on, try it - everyone should have this experience). If you need something other than Debian, there are also some live CDs based on Red Hat and on BSD, but I haven't tried these as yet. Use Google and DistroWatch if you want to find them.