Recently I had a hard drive failure that pushed me into getting a little NAS device that I could back up to S3 easily. After consolidating a lot of data to the NAS I was left with a few old hard drives that I needed to do something with as well as some existing hard drives that I've collected over the years. Some of the drives I have are from family members that I have recycled computers for but kept the hard drives out of fear that personal data might still be on them. At the same time this was happening I read an article claiming that a single drive wipe protects data.
I started digging a little more to see just how effective a single drive wipe might be and found the old wisdom in this article: Secure Deletion of Data from Magnetic and Solid-State Memory. Scanning over this older article I noticed that it had been updated with a response to the latest article on the effectiveness overwriting a drive with a single pass random data. After reading through the articles I decided that overwriting was good enough. I figure if it doesn't completely destroy the data it will make it hard enough to not be worth recovering.
The first step I took was to get a Knoppix live CD. Doing this let me remove data on any drive that I could connect to the PC. The next step was to run the shred command on each disk that I wanted to destroy (shred happens to be on the Knoppix live CD):
The options I used have the following meaning:
z – zero the drive once the random passes are done
v – verbose, shows the progress
n – number of passes to make writing random data
You can have shred make as many passes as you want and the default is 25 passes as described in Secure Deletion of Data from Magnetic and Solid-State Memory. Depending on how fast and how large the drive is this command can take a really long time to run. I decided that 3 passes would be good enough for me. I will still probably hold on to most of the disks in question just in case I want to use them later but I now don't feel like I can't toss them if I no longer need them.