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Date:      Sat, 02 May 2015 17:59:02 -0453
From:      "William A. Mahaffey III" <wam@hiwaay.net>
To:        freebsd-questions@freebsd.org
Subject:   Re: How to restore a USB drive converted to bootable
Message-ID:  <5545553F.50602@hiwaay.net>
In-Reply-To: <20150503002420.fdcc9310.freebsd@edvax.de>
References:  <5543FAA3.7050907@hiwaay.net> <441tiz3wrx.fsf@lowell-desk.lan> <5544DBA2.1030102@hiwaay.net> <20150502233854.c80bc5ae.freebsd@edvax.de> <55454CDA.3020209@hiwaay.net> <20150503002420.fdcc9310.freebsd@edvax.de>

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On 05/02/15 17:30, Polytropon wrote:
> On Sat, 02 May 2015 17:23:13 -0453, William A. Mahaffey III wrote:
>> On 05/02/15 16:45, Polytropon wrote:
>>> On Sat, 02 May 2015 09:20:09 -0453, William A. Mahaffey III wrote:
>>>> On 05/02/15 09:06, Lowell Gilbert wrote:
>>>>> "William A. Mahaffey III" <wam@hiwaay.net> writes:
>>>>>
>>>>>> I am about to do some OS installs (NetBSD & OpenBSD, as it happens) on
>>>>>> boxen under construction. I would also like to use UBCD on a flash
>>>>>> drive to memcheck those boxen prior to installation. If I prep a USB
>>>>>> thumb drive as either a bootable UBCD drive or an over-the-WWW
>>>>>> installer, I wipe out the drive for its original use. Is there a way
>>>>>> to restore the drive back to its original functionality if I wanted to
>>>>> Is "wipe the drive and reformat" what you need to hear, or do you have
>>>>> more requirements that you haven't made clear?
>>>>>
>>>> Wipe & reformat, preferably from CLI under FBSD 9.3R-p13 for
>>>> convenience, is what I'm after. Clearly creating a bootable UBCD or
>>>> installer will wipe out whatever was
>>>> there before, so I just want to get back to 'virgin' USB drive.
>>> In that case, the command
>>>
>>> 	# dd if=/dev/zero of=/dev/da0 bs=1m count=1
>>>
>>> should be fine. If there is any offending GPT metadata located
>>> at the end of the USB drive, estimate the size and also erase
>>> the last few MBs (use skip= to do so). There is no need to
>>> actually zero out the _whole_ drive.
>> *Aaaaaaaaaaaaaaahhhhh*, I wasn't sure about that (zero the whole drive),
>> thanks :-) ....
> There are only few significant "data zones" on the USB drive.
> The boot sector and partition table are located at the beginning,
> and _maybe_ GPT metadata at the end. Removing both makes the
> remaining bits and bytes practically useless (except when you
> take it to forensics, but you don't want to recover things
> anyway, so the result should work for you).
>
> However, if you want a USB drive "new" (as in "I just bought it
> from the shop, it's fresh out of the package!"), then you have
> to write a MSDOS (FAT) file system, install some crapware, some
> ridiculous "drivers", and "value added" software, maybe with
> some spying tools, malware, nagware, and non-working "encryption"
> tools. Add several partitions and make them smaller than the
> real size of the drive. And add a "Facebook" link. :-)
>
>
>

I was thinking of dd-ing the 1st MB or 2 off into a file, then restoring 
from that file when done, that would skip all the extra features you 
mention ;-). Would 1 or 2 MB be enough to get all of the FS info ? I 
wasn't aware you didn't have to zero everything out, that simplifies 
things a fair bit ....

-- 

	William A. Mahaffey III

  ----------------------------------------------------------------------

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.




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