[PLUG] PSU library scanner, USB thumb drive with no listed files

[Russell Senior]

Do you see anything that looks like a file allocation table? It's been a
long time since I cared much about dos filesystem details.

On Sun, Jan 12, 2020 at 3:57 PM Russell Senior <russell at personaltelco.net>
wrote:

> Step 1 is to dd the whole USB drive to a backup image. Then from a copy of
> that backup image you can start trying recovery from that.
>
> On Sun, Jan 12, 2020 at 1:32 PM Keith Lofstrom <keithl at kl-ic.com> wrote:
>
>> The three book scanners near the checkout desk at the
>> PSU Millar library are somewhat difficult to use, but
>> better than my slow USB flatbed scanner at home.
>>
>> Yesterday I scanned three huge multipage files to a
>> Brand X "Cheap on Amazon" 2GB USB flash drive.  I was
>> in a hurry,  so I did not segment the files into smaller
>> chunks, or check the files with my laptop as I made them.
>>
>> Bad idea.
>>
>> I now have a flash drive which is 60% full, but no files
>> are listed in the directory.  Either the files were too
>> large for the scanner, or the 40 character file names were.
>> The flash drive is formatted for VFAT16 DOS or somesuch.
>>
>> I hope to recover the files (if not the file names) and
>> avoid another 90 minute, 200+ page scanning marathon.
>> I can grep the drive image for strings; I don't see the
>> filenames, but grep shows about 100 strings like
>> /ProcSet [ /PDF /ImageB ] -or-f /ProcSet [ /PDF /ImageC ]
>> and some fragments.  I tried using "testdisk" tools to
>> recover the three files; no joy.
>>
>> My best guess is that my overly-long scan files blew
>> the memory buffer on the PSU scanner, and it overwrote
>> garbage.  There are signs above the scanners to "save
>> frequently" which I ignored (https://www.xkcd.com/293/)
>>
>> PERHAPS SOMEONE CAN SUGGEST CLEVER TOOLS to extract the
>> pdfs from the 1.2 gigabytes of "unlabeled something" on
>> the flash drive.  Knowing how might help me help others
>> in the future.
>>
>> I expect I will only get my files by scanning them
>> again, properly, in small chunks PSU's feeble scanners
>> can handle.  Meanwhile, "don't do that" is probably the
>> most help I can offer to others.
>>
>> Keith
>>
>> P.S. - the best book scanner I've used was at MIT Barker
>> Library; it images the book open 120 degrees, face up,
>> and accomodates the natural curve of the pages.  The book
>> scanners in the Library of Congress are almost as good,
>> but you must stretch the pages flat to get focused images.
>>
>> --
>> Keith Lofstrom          keithl at keithl.com
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>