Wiping Free Space on Drive

A friend of mine has an old iMac (the kind with the half-globe base) that she needs to get rid of. Before I’ll let her do that, I want to clean it up and securely erase the free space. She no longer has the installation media and the system does not have WiFi. Now, I’m not a Mac person (since the Mac II days) and don’t know what software to use for this.

Is there a (preferably free) utility that anyone can recommend?


I presume she is running an eRly version of MacOS X (possibly Tiger).

Make a new admin user. Delete her user account. You might get the option to securely erase it.

Then start Disk Utility which is in Applications -> Utilities and should have an option to erase the free space

I use this:

dd if=/dev/zero bs=2m of=~/junkfile

Let it run til it fills the drive and then delete it.

How old is the iMac? where in San Diego are you? perhaps I can help… Somewhere around here I have the original CD for Tiger (or later I think)

How old is the computer? Drop it - problem solved.

Not in San Diego at the moment, Dave. Visiting the friend in Chicago.

As for it’s age, she got it back in 2003 or 2004. I’m not sure what OS version is one it.

Tim, I think your approach will likely be the one I resort to if Disk Utility doesn’t get it done.

There’s a lot of road excavation and repairs going on around here. Maybe I’ll see if I can give it an asphalt burial. :slight_smile:

If you are going to recycle the computer (not give it away or sell it)… .The Disk Utility has a 7pass DOD level reformat option… this will insure that NOTHING could ever be recovered… However bear in mind it can take a day or two to run depending on how large the disk is////

The other option… is a Drill Press :slight_smile:

+1 Dave :slight_smile: - For simple destruction, we also use a Makita drill with a 1/2" carbide-tipped bit followed by a couple of blows with a 12# sledge hammer.

Thermite is your friend :smiley:

yeah, but Law Enforcement kinda frowns on thermite possesion

like AC/DC says “TNT” :smiley:

Throw-away culture … how sad …

… at some point you’ll learn that there’s no such thing as a throw-away planet …

That historical computer with Good Old Software, Games, and so on? :o

I don’t intend to destroy it. If that were my intention, I’d simply disassemble it and repurpose the components. I need to wipe it since she intends to donate it to charity.

In that case, booting form a Mac OS DVD/CD and Opening the “Disk Utility” then doing a secure erase on the complete drive followed by a reinstall of Mac OS will be your best bet.

Then do the most destructive level of reformat that DiskUtility offers, there really isn’t any secure way to sanitize just “free space”, meaning you’d have to reformat the drive, and reinstall macOS… check with a local Apple Store, they might do it for you (as they have access to older versions of OSX), since you don’t have a copy

If you just do a “standard” reformat, it doesn’t erase anything, just reconfigs all the file tables, marking areas as rewriteable

diskutil secureErase freespace (level 0-4) /Volumes/(Drive Name)

from http://osxdaily.com/2016/04/28/erase-free-space-mac-command-line/

??? What makes you think / say that?

If we would be talking about SSDs then you’d have a point, but hard disks? No.

Between 25 and 30 years ago this does nothing more than a standard initialization * (in the System 7 / 8, Pre 9 times).

Now ? I do not know. I do not have tools to read the hard disk contents (read blocks as as hex, not read files).

  • I am talking about the process that takes hours to complete, not erase who takes some seconds to whipe the items pointers in the hard disk Table of Contents.

Dave, on standard HD, do we need to do that to be sure nothing (no data) from the hard disk survice ?
(do not be fooled by TV "specialists, they said “white lies” for the scenario !).