Lately, my favorite Linux live-cd is SLAX. I run Gentoo on my main system, but a live-cd is useful in a number of situations. I've used KNOPPIX in the past, but it is getting to be a little heavy for my tastes, with versions now taking up the better part of a DVD. SLAX is nice and small, just under 200Mb currently - quicker to download and burn in those "I need a live-cd NOW" situations. Since I'm more interested in having a toolkit that I can use in certain situations as the need arises, rather than a fullblown system for day to day use, the smaller live-cds fit my needs better.

Ironically, my primary use of Linux live-cds over the past few years has been as a tool to rescue Windows systems that have become unbootable, either from spyware/viruses, hardware failures (thanks Dell! Twice!), or random acts of Windows weirdness. In those sitations, I will boot from the SLAX CD, copy the Windows data across the network to my primary Linux box via samba, wipe the disk with dd (so the Windows installer doesn't try to "repair" the bad system), then rebuild and copy the data back over samba.

This weekend we decided to clear out a closet of old computers and donate them to charity. The problem was that most of them had been used in a family business and contained confidential client data that we didn't want to ship out to the world. Some of the machines were bootable, some were not, but clearly, booting into Windows and trying to delete the files from a running system was a bad idea (first, it is hard to know you've gotten everything, and secondly you can't wipe the entire system while it is running). So, time to boot into a SLAX live-cd. In this case, a plain dd would have done the trick, but just to cover every base (i.e. to prevent getting sued) I used the shred utility. The shred utility will overwrite the data multiple times with random data patterns to prevent data recovery by even the most expensive recovery equipment.

Happily, I found that shred was installed on the SLAX CD, so it was a simple matter of issuing shred -v /dev/hda to wipe the entire disk. This wipes the entire hard drive device at once, and is superior to mounting the drive and wiping the files (especially if you had a journaling filesystem on the drive where shred cannot guarantee that the wiping will succeed). When run as above, shred will overwrite the data 25 times. From what I've read, 7 times should be sufficient to defeat known capabilities to perform recovery, so 25 should be extreme overkill. If you want to save time, you can switch to 7 (or however many) overwrites by issuing shred -v -n 7 /dev/hda instead. I was lazy and not in any particular hurry so I let it run the full 25. (By the way, SLAX auto-mounts all the hard drive partitions it finds, so you should unmount those before running shred on the drive.)

I ran this procedure on everything from Pentium II's, AMD K6's, and Pentium III's with no hitches whatsoever. Nice job SLAX!