So today, I finally retired my old work laptop. As I’m a relatively security-conscious person when it comes to my old hard disks, I thought I’d share what I did.
So today, I finally retired my old work laptop. As I’m a relatively security-conscious person when it comes to my old hard disks, I thought I’d share what I did.
First off: Even if you “delete” all the information on your hard disk, it’s still there. Yep. A format doesn’t get rid of it, and it’s possible to extract that old data. There’s only one way to permanently delete so that it is unrecoverable without physically destroying the disk: use a utility which overwrites the data with something else.
But just one time won’t do it. You have to overwrite it a bunch of times, because the old data still lurks as a magnetic “shadow” of its former self, right there on the disk underneath the data.
Enter “shred”. You can boot from any Linux Live CD (Gentoo, Ubuntu, and SuSE all have one), and there will be a little utility called “shred”. You will probably have to download and burn an ISO image first to get a copy of Linux.
Once you have the CD burned, boot to it, and type the following commands at a terminal window (The “$” and “#” indicate a prompt, you don’t type that):
$ sudo bash # shred -vfs /dev/hda
This will take a few hours, but once it’s done, you can rest assured that your old data is unrecoverable by all but the most expensive and time-consuming recovery methods, and then, it will probably be only a partial recovery, if any. Your hard drive will be safe to sell on eBay or whatever.
Now, if you want to be really pedantic, rather than overwriting the default 26 times (25 times with random data, 1 time with zeroes at the end), change the flags to “shred”:
# shred -vfs -n 100 /dev/hda
This would erase the data 101 times in a row (100x with random noise, 1 time with zeroes for a final pass). It may take a weekend to complete, but that hard drive will be clean and ready to get rid of without compromising your personal information.
As the coup de grace, of course, on this hard drive I have in the laptop before me which is being shipped back for destruction, I will install Ubuntu Linux. Just to remind whoever gets the machine that I am, after all, a budding Linux guru. Fear me.