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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.
A Ubuntu-derived distribution, Puredyne bills itself as an "operating system for creative multimedia" designed to run on a USB drive.
More specifically, Puredyne contains free software tools for audio, graphics and multimedia, as well as for streaming and version control. In each of these categories, the tools range from command line tools to the latest available on the desktop. Its graphic tools, for example, include both ImageMagick for batch processing files from a terminal, GIMP for photo editing and Inkscape for creating your own graphics.
Just as importantly, Puredyne includes a range of equivalent tools. Version control tools, for instance, include Subversion, Mercurial, and Bzr, only one of which any user is likely to want. This variety makes Puredyne a showcase of free software tools, as well as an environment well suited for productivity.
No list of Live Disks would be complete without a forensics disk for investigating system failures and restoring them. CAINE (Computer Aided INvestigative Enivronment) is only a few months old so far as I can tell, but worth mentioning for the thoroughness of its selection of applications.
To start with, CAINE incudes an extensive list of standard security tools, including john, wireshark, LVM2 and FRED. In addition, CAINE includes WinTaylor for analyzing Windows systems. It also includes a report creator with a simple but effective interface.
The function of this Live Disk is self-explanatory. What is less obvious until you try it is Redo's versatility. It can be used on both Linux and Windows, stand-alone machines and networks, and not only for backup, but also for recovering lost files and configuring partitions. Among these tools, the backup is especially noteworthy for its simplicity. Needed drivers or documentation can be downloaded as well via Redo's own Internet connection.
Sugar began as the interface for the One Laptop Per Child project. However, for several years, it has been an independent project overseen by Sugar Labs, which develops a desktop environment for early childhood education. Sugar on a Stick is a Fedora re-spin whose goal is to encourage the use of Sugar among its target audience.
From the perspective of a user familiar with standard desktops like GNOME or KDE, Sugar is a radical simplification. Its home view displays available activities -- the term used rather than application to emphasize the educational aspects -- in a circle. Activities are launched full-screen. A unique feature is its neighborhood view, which shows nearby Sugar users with whom users could interact.
Those with children might want to investigate Sugar on a Stick as a way to introduce them to computers.
Do you want to explore security and privacy? If so, then Tails is one of the most painless places to start.
Tails is a live system designed for safe and anonymous Internet use via the Tor Project. The makers of Tails, many of whom prefer to remain anonymous, have made security and privacy available to anyone who can boot a Live Disk. It even includes a camouflage option when you are using it in public, disguising itself as Windows XP to deflect curiosity from passersby.
However, as useful as Tails is in itself, what may be even more valuable are the online help provided by the project and the links to Tor's documentation. Half an hour's reading will leave you aware of the legitimate reasons for privacy and the basic principles needed -- all of which you can then see in action via Tail's Live CD.
A Part of the Culture
These are only a sampling of the Linux Live Disks available, but they give some sense of the variety.
Almost certainly, the list is incomplete, but it gives a sense of how much Live Disks are a part of free software culture. Somewhere on that list, you are sure to find one that interests you. Live Disks are so much a part of the user culture that, sooner or later, you will find yourself using one -- and probably several.