Linux Server Hacks, Volume Two

Hack #98. Permanently Delete Files

Deleting a file typically just makes it harder to find, not impossible. Using a simple utility to write over files that you delete can help ensure that your data is gone for good.

We all store personal, secret, or potentially embarrassing data on our machines at one time or another. Whether it's last year's tax returns, instructions to your bank in the Cayman Islands, or a risque picture of your husband or wife, everybody has some data that they don't want anyone else to see, and no one keeps their computers forever. What do you do with your old machines? In business environments, they often simply get passed down the user food chain until they die. Are they wiped clean before each transfer? Rarely.

As we all know from the various Windows utilities that have been around for years to enable you to recover files (and from "Recover Deleted Files" [Hack #97] and "Recover Lost Files and Perform Forensic Analysis" [Hack #100] ), just because you've deleted a file doesn't mean that it's actually gone from your disk. There's a good chance that the data blocks associated with any deleted file are still present on your disk for quite a while, and could be recovered by someone who was desperate or persistent enough.

You probably won't be surprised to hear that Linux, the OS of a thousand utilities, provides an out-of-the-box solution for truly deleting files. To recover a deleted file, you must reassemble the file, either by walking through the free list ...