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Subject: Re: Unusual Question
To: Doug Hardie <bc979@lafn.org>, David Christensen <dpchrist@holgerdanske.com>
Cc: freebsd-questions@freebsd.org
References: <888578F8-AD68-4993-823C-152789F3C929@mail.sermon-archive.info>
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From: Arthur Chance <freebsd@qeng-ho.org>
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Date: Fri, 14 Jul 2017 08:26:50 +0100
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On 14/07/2017 07:11, Doug Hardie wrote:
> 
>> On 13 July 2017, at 21:44, David Christensen <dpchrist@holgerdanske.com> wrote:
>>
>> On 07/09/17 02:57, Doug Hardie wrote:
>>> I have a FreeBSD 9.3 remote server that needs to be purged.  I know that rm -rf / will remove all the directory entries, but I need to write over the drive.  I thought that dd if=/dev/zero of=/dev/ada0 might do the trick, but it gives an not permitted error.  The whole thing can crash and burn at the end.  This is an unmanned site so moving drives is not viable.
>>
>> If the machine has BIOS and the system drive isn't too large, write an assembly program that fits into the MBR bootstrap code area to wipe the rest of the drive, assemble the program, write it into the MBR, and reboot.
>>
>>
>> Bonus: the program deletes the MBR when done wiping the rest of the drive.
> 
> Neat idea, but I have a number of these systems and they all use different disk drives.  That would be a lot of work writing drivers for each type.

How about using the BIOS extended write sector call (INT 13h, AH=43h) in
your code? That should be portable.

-- 
An amusing coincidence: log2(58) = 5.858 (to 0.0003% accuracy).