However, no other segment of IT has made Live Disks so much a part of their culture as the open source community.
Most major Linux distributions use Live Disks for installation because they are a quick way to test-drive an operating system without changing a computer's setup or endangering its contents. When using a Live Disk, at worst, you may need to reset the BIOS temporarily to boot from an external device, and users have to set about deliberately to alter files on the hard drive.
Live Disks are especially handy for checking hardware support on a machine before purchasing -- assuming, that is, you can find a store clerk who knows what Live Disks are and has no fear that they might contain malware.
Another common use for Live Disks is for creating spins or remixes. These are variants of an official disk image to localize it for a particular culture or desktop environment. Tools like Fedora's livecd-creator make this task possible even for inexperienced users, requiring little more than the ability to follow instructions.
Other Live Disks are designed for system recovery, administration tasks or as stand-alone operating systems for a specialty purpose, such as video editing. Increasingly, these specialty disks are put on flash drives, and provide persistence, or the ability to save files to the drive, which early Live Disks lacked.
Like distributions, Live Disks come and go. However, among the hundreds of Live Disks available for the download, a few especially useful Live Disks have survived for a number of years and stand out either because of their basic functionality or their selection of applications:
One of the first Live Disks, Knoppix is still one of the most popular. Released in English and German, Knoppix comes in a compressed CD or DVD, and is the basis for dozens of derivatives.
In many ways, Knoppix is an all-in-one Live Disk. Users can install it -- although relatively few ever do -- demo Linux with it, or use it as a basic rescue disk. It is especially known for its extensive hardware support. This versatility makes it handy to have around.
2. & 3. GNOME Partition Editor (GParted) and Parted Magic
Disk partitioning is mostly important during installation. However, if you have multiple operating systems installed or use multiple partitions to make recovery easier if disk corruption happens, then you may find yourself using disk partitioning several times during the life of your hard drive.
You could use GNU Parted to partition. However, while GNU Parted does a perfectly adequate job, you may prefer to use a tool with an interface instead.
That's where GParted and Parted Magic become useful. More or less equivalent to each other, both support creating, moving, resizing and deleting the most common filesystems, including not only ext4, linux-swap and NTFS, but also btrfs and reiser4. Both depict hard drives as a bar-graph, with each filesystem color-coded. If there is an overwhelming reason for using one instead of the other, I haven't noticed it. One or the either should be part of your basic toolkit.
Super GRUB Disk's toolset has changed as distributions switched from legacy GRUB to GRUB2 for a boot manager. However, the latest version still allows you to boot a Linux system and then restore the boot manager with the command grub-install /dev/sda. It also includes useful features such as booting OS X and booting from a USB drive into systems with no USB support in the BIOS.
Super GRUB2 Disk is also the core of Rescatux, a more ambitious -- and, naturally, much larger -- rescue disk.
With tools to check and fix filesystems, to re-create the user's list for the sudo command and to change passwords, Rescatux is primarily designed for Linux. However, the current release also restores Window's master book record and removes Windows passwords, with more features for recovering Windows systems planned.
However, what makes Rescatux particularly useful is that these functions are presented in the form of wizards. Consequently, Rescatux is a recovery tool that requires minimal knowledge, making it usable by anyone. (If you are trying to recover a Windows system, you might also look at BootMed.)
DBAN's purpose is to delete the contents of any hard drive on a system. The project site is quick to state that DBAN comes with no guarantees, but I know of at least one non-profit that finds it reliable enough to wipe old systems before refurbishing them and passing them along. You might want to use it as the last thing you do on an old system to remove all your personal information or as a last-ditch effort to remove viruses and spyware from Windows.