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Date: Fri, 7 Oct 2011 12:53:22 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Arnaud Lacombe <lacombar@gmail.com>
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Cc: Poul-Henning Kamp <phk@phk.freebsd.dk>, freebsd-current@freebsd.org,
	Benjamin Kaduk <kaduk@mit.edu>
Subject: Re: aliasing (or renaming) kern.geom.debugflags
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On Fri, 7 Oct 2011, Arnaud Lacombe wrote:

> Hi,
>
> On Fri, Oct 7, 2011 at 2:13 PM, Warren Block <wblock@wonkity.com> wrote:
>> On Fri, 7 Oct 2011, Poul-Henning Kamp wrote:
>>
>>> In message <alpine.GSO.1.10.1110071341430.882@multics.mit.edu>, Benjamin
>>> Kaduk
>>> writes:
>>>
>>>> Now, an ordinary user who is
>>>> doing this for the first time might ask, "why do I need to do something
>>>> with 'debugflags' in order to make a USB stick?
>>>
>>> Which is the exactly right question to ask.
>>>
>>> The procedure documented is clearly flawed.
>>
>> Probably a misunderstanding on my part, since I suggested it to Glen. Can't
>> recall the circumstances exactly.
>>
>> The next question would be: what is the correct procedure?
>>
> I'd guess the procedure involves shooting your feet:
>
> from `sys/geom/geom_subr.c':
>
>        /* If foot-shooting is enabled, any open on rank#1 is OK */
>        if ((g_debugflags & 16) && pp->geom->rank == 1)
>                ;

Well, yes.  The goal is to unprotect the device, regardless of what may 
already be on it.  Then the user can overwrite it with the memory stick 
image.

The current documentation is

   sysctl kern.geom.debugflags=16
   dd if=memstick.img of=/dev/whatever0 bs=64k