How do you completely wipe out a hard drive without the aid of a CD?


I finally got this damn iMac to boot up and now it's running off of OS 9.

...I'm going to sell it and I wanted to know if there is a way to completely clear out the hard drive without having to drag and drop everything to the trash and/or reinstalling OS 9 or a new operating system.

Is there a menu somewhere that will do this?


Notorious Olive Counter
Dropping stuff in the trash doesn't really clean it up - the data is left on the drives still.

And, you can't wipe the drive while the computer's trying to run an OS off it - it would be like sawing off a branch you're sitting on. If you boot off the OS X CD, you can format the drive, with the option of wiping it thoroughly.

I know, you said "without the aid of a CD". The answer to that one is, not likely, I'm afraid.


Disk Utility. Erase the hard drive and set what kind of erase you want on it. On Tiger, you even have the option for a 35-pass wipe. That's hardcore.


If the iMac is new enough to have FireWire, you can wipe it via target mode. Turn off the iMac, connect it via firewire to another mac, then start up the iMac with the 't' key held down. The imac will boot with a firewire symbol on the screen, and its HD will show up mounted on the other mac. Then use your utility of choice to erase it.


Rosie Moderator
Staff member
It sounds like you are going to sell the iMac with out an OS installed, i.e. not workable.

If you are going to sell it, I suggest you use an OS CD to wipe the drive clean and install the basic OS.

Think about if you bought a computer, was told it works, plug it in, and get a big question mark. Please make is usable for the new owner. ;)


U.S.D.A. Prime
Short answer: you cannot completely wipe the drive clean while being booted off of the drive. You must find an alternate way to boot the computer so you can wipe the internal drive clean, like an OS install CD or another Mac/hard drive.


I'm trying to wipe my computer as well and I hooked it up to another mac but when I tried to erase everything an error came up saying unable to unmount disk. What do I do?