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

[Timothy Boyden]

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.


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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