[Macpartners] Zeroing sectors of just one volume (on a partitioned drive)

[Kerem B Limon]

Quoting Timothy Boyden <trboyden at MIT.EDU>:

> According to this posting, apparently you can do the same thing using 
> the UNIX 'dd' command:
> 
> ***********
> bdl
> 08-16-2002, 05:03 PM
> Best way I've found to wipe a drive, data, partition table and all is to 
> just use the 'dd' command under linux (or possibly BSD, I can't confirm 
> atm). You just issue the command
> 
> 
> $ dd if=/dev/zero of=/dev/hda bs=1M count=38172
> 
> 
> Where the device is your drive device and the count value is the size of 
> your hdd.
> Some SCSI controllers also have this function built in, when you boot up 
> and enter the SCSI utility screen you'll see it.
> 
> ************
> 
> Instead of the output file being the drive, you could point it to your 
> partition. 'dd' is a powerful command and if your not sure how to use it 
> properly I would reccomend not trying it. There is lots of information 
> online about it if you want to give it a try though.
> 
> 

Ah, yes. Of course, unless you provide some random input (possibly from
/dev/random, if it exists on the system), this is just zeroing and not random
overwrite, but that's what David originally wanted, anyway, I think.

-Kerem

> Tim Boyden
> MIT Department of Facilities
> IT Group
> 
> 
> Timothy Boyden wrote:
> 
> > Although not free, SuperScrubber from Jiiva Software 
> > (http://www.jiiva.com) $29.99 claims to securely erase data from 
> > internal or external hard drives and partitions.
> >
> > Honestly I'm not sure how secure this approach would be given that due 
> > to defragmentation data gets written all over a hard drive so even if 
> > you did zero just one partition, data from that partition may still be 
> > on other parts of the drive and recoverable through professional means.
> >
> > A better approach would be to copy the data you want to keep to 
> > another drive, zero the old drive and copy the saved data back to the 
> > old drive. It's going to take awhile to zero the drive anyways so the 
> > extra step of copying the good data won't mean much in the end. Also 
> > it's a safer method given something could happen to the good data 
> > during the zeroing process of the one partition.
> >
> > Tim Boyden
> > MIT Department of Facilities
> > IT Group
> >
> > David M Rosenberg wrote:
> >
> >> With Apple's Disk Utility (version 10.4.4 in MacOS X 10.3.9), when
> >> you go to erase an entire drive there is an "Options..." button that
> >> has checkboxes for the following two options:
> >>
> >> Zero all data (writes zeros to all sectors of disk)
> >>
> >> 8 Way Random Write Format
> >> (writes random data over entire disk eight times)
> >>
> >> However, if I go to erase one volume on a disk drive, the "Options..."
> >> button is disabled and I don't see a way of zeroing all the sectors of
> >> just one volume.
> >>
> >> Does anyone know how to zero all the sectors of one volume without
> >> effecting other volumes on the same drive with either Apple's Disk
> >> Utility or some other free utility?
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Kerem B. Limon
kerem.limon at mit.edu /e-mail