Re: how to rescue this backup data

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

> dd if=/dev/sr1 bs=2048 skip=1256112 count=1 | od -c | head -n 1
> 0000000 001   C   D   0   0   1 001  \0   L   I   N   U   X            

Ok.

>  dd if=/dev/sr1 bs=2048 skip=1256112 count=1 \
>   | dd bs=1 skip=158 count=4 | od -d
> 0000000 46890  4864
> This value surprised me a bit, it is unlikely
> even close to a possible offset.

Indeed. 4864 is much too high.

The bytes in question are:

> 0000220  ...  267   *
>          ...    b72a
> 0000240 023  \0  \0 023   * 267  
>         1300      0013    2ab7 

man ascii ... 
Your od -d probably interprets 16 bit words MSB.
We need LSB, resp. have to read the MSB duplicate
= 0x00132ab7 :

  $ expr 19 '*' 65536 + 42 '*' 256 + 2 '*' 64 + 6 '*' 8 + 7
  1256119

That would be an offset of about 2.4 GB.
(please check my conversion of 0x132ab7 by
 a hex calculator)

So my bet is 
  1256119 - 28 = 1256091
provided that your first sessions show
  1c00 0000
at byte 158 (octal 0236) of block 16.


Have a nice day :)

Thomas