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Date:      Sun, 03 May 2015 10:22:29 -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:  <55463BBE.9000904@hiwaay.net>
In-Reply-To: <1701096.lYLT1Yt70m@amd.asgard.uk>
References:  <5543FAA3.7050907@hiwaay.net> <20150503002420.fdcc9310.freebsd@edvax.de> <5545553F.50602@hiwaay.net> <1701096.lYLT1Yt70m@amd.asgard.uk>

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On 05/03/15 05:36, Dave wrote:
> On Saturday 02 May 2015 17:59:02 William A. Mahaffey III wrote:
>> 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 ....
>>
> That might be enough if you are then going to put it in a drawer, not use
> it all, then restore those same few MB later.
>
> If you are planning on installing UBCD onto it in a some form of bootable
> filesystem them I'd suggest you need to DD *at least* the size of UBCD so
> you can restore any/all existing data.
> You could just DD the entire pendrive and pipe it through tar/gzip if you
> really want to be able to put back exactly as you found it since you don't
> really know exactly where on the drive the data is.
>
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>

I'm not sweating the data, just the functionality .... If I overwrite it 
w/ UBCD or something similar, I know I lose all data there, so that's no 
problem, I just want to (possibly) be able to revert to previous 
functionality ....

-- 

	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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