An oddity of open source operating systems is the Live CD. It’s not something you’re likely to see coming out of Redmond or Cupertino any time soon, but for a few years now many Linux distros and versions of BSD have given this option. Recently, Live DVDs and Live USB have cropped up as well. These live systems are full versions of the operating system that run completely from the given medium. Which means you can carry them in your pocket and use them on other computers. They do not, by default, touch the hard drive, so they are completely safe to use.

Live CDs originally came from the old boot-disk-for-diagnosis idea. For example, Knoppix, known for its hardware detection, is often used for testing hardware. While Knoppix may not use the best driver for the hardware, if the hardware is functional it should work. If the hardware doesn’t work in Knoppix, it very likely needs to be replaced.

Some Live distros, like Helix are tuned to a special purpose. In the case of Helix, that purpose is forensics or data recovery. For penetration testing (network security), Backtrack is popular.

Test-drive a distro before installing it

Live CDs have now become a way to test-drive a distro before installing it. This can be really useful when dealing with finicky hardware. Instead of wasting time installing different distros to find one that supports your wireless card easily, you can just try the Live CD for a few minutes. These test-drive Live CDs also give you a chance to feel out how a distro functions. Different distros have different default configurations, desktop environments, and different ways of doing things. You can try a few out without going through an installation to find the one that suits your personal workflow.

You can also use a Live CD as a way of gaining familiarity with a distro before installing it. A new environment can be a bit intimidating, and that can make installation scary. Spending some time in the live environment to get your footing and “practice” your usual tasks while knowing that you can easily go back to your old system where nothing has changed can take away a lot of the anxiety associated with making such a big change to your computer.

You’re secure

In addition, a desire for added security can be a good reason to use a Live CD. When using public terminals or computers whose owners you know are unlikely to ever have run a virus scan a Live CD can be very handy. What if that random computer has spyware? What if there’s a keylogger? What if someone used the USB Hacksaw on the computer? If you boot from a Live CD, none of those (well, except a hardware keylogger) will affect you. Your stuff is still secure.

Of course, a Live CD can also be a way around security. From a Live CD, you have full root access to the underlying system. This is one of the reasons they are used for system repairs. It’s like taking the hard drive out, putting it in an enclosure, and hooking it up to another running system to mess with it, except a lot more convenient, since you don’t need the other computer and the enclosure. Ways of blocking others from doing this to access your hard drive include setting the CD drive to not be bootable and then adding a BIOS password to keep anyone from changing that, but with physical access that’s easy enough to circumvent. With physical access, whether they’ve got a Live CD or an enclosure, there is no such thing as security anyway. That is why many companies and governments are requiring that their employees’ laptops use full-disk encryption nowadays.

Create your own Live CD

What’s becoming popular now is rolling your own custom Live CD. Revisor is a new tool for creating customized Fedora Live CDs and install disks.

For Ubuntu, there are Reconstructor and Remastersys, though Remastersys works for other Ubuntu-based systems like Linux Mint as well. Besides these GUI tools for creating Live CDs, those who are already using Linux can create custom Live CDs for their friends by using the mklivecd tool to make a Live replica of the installed system. You can carry a customized operating system built to suit your needs and preferences in your purse!

Mackenzie is a college student who likes to promote Linux and Free/Libre Software. Most of her free time is spent on the computer, helping new users, or hanging out with some of the friends she’s made in the Linux community. Check out her blog, Ubuntu Linux Tips & Tricks.