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Re: recovery recommendations



A simple one would be:
dd if=/dev/zero of=PARTIMAGE bs=1M count=184
(presuming that your original ISO was 185MB.  -- this leaves up to 1MB of random crap, but (in my mind), that's better than tashing the good bits of data.

You can get more accurate results by varying the block size and the count so that they multiply out properly.
modern versions of DD recognize multipliers of K -> kilobytes, M->Megabytes, G->gigabytes
  .. and those are the CS units (now called kibibytes, mebibytes, gibibytes), not the marketing units.


On Sat, Jan 22, 2011 at 5:57 AM, Matija Nalis <mnalis-ml voyager hr> wrote:
On Fri, Jan 21, 2011 at 10:51:20PM +0100, Florian Weber wrote:
> * Keep a copy of your "unrecovered" disk image! You don't want to touch the
>    original disk at all, so be prepared for making mistakes

yes, that is always the most important step. And be extra extra carefull you
don't nuke it by accident... readonly jumper on the drive (if it has one)
helps.

> * dd if=/dev/zero of=PARTIMAGE count=ISOSIZE
>    where ISOSIZE is the ISO image's size in bytes

actually, it is ISO image size in *blocks* [1], so this procedure would
actually destroy 512 times more data than original error... :-|

Anyway, let us know how it worked out...

And if this procedure fails you, I'd also second the great experiences with
http://www.cgsecurity.org/wiki/PhotoRec - works even if filesystem and
partition structures are completely foobared...  If you use it and it works
for you, don't forget to donate to the guy, there's link on the pages.

[1] by default block size is 512 bytes, can be changed with bs= parametar to
   dd(1) -- note that while you can use 1 byte as an unit, it will be terribly
   slow; so it is probably best to use let's say bs=4K, divide ISOSIZE in bytes
   by 4096, round it down to nearest integer, and use that as count= parameter.

--
Opinions above are GNU-copylefted.

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