Occasionally I give away (or sell) an old Mac that I'm not using anymore. Before I do that, I want to make sure that none of my personal data remains on the drive, but I'm too lazy to reformat the drive and reinstall the OS. Instead, I do the following:
- Create a new Administrator account
- Log in using the new Administrator account
- Delete all the other existing user accounts (this step deletes all home folders, and therefore hopefully all personal information in those home folders)
Open a Terminal window and enter this command:
dd if=/dev/random of=bigfile.bin
Let that command run until bigfile.bin has eaten up all of the free space on the drive, and the command terminates with an "error, out of disk space" message.
- Delete bigfile.bin to free up disk space again.
I think that for all practical purposes, filling up the hard drive's free space with random data should make it impossible for anyone to use an "undelete" utility to recover any files that were deleted in step 3.
The question is, is this process actually sufficient? Or is there something that I'm overlooking that could allow my personal data to "leak" despite the above? (Note that I don't consider the applications installed in the /Applications folder to be personal data)