impossible to restore MBR using dd

[Cliff Hones]

Matthias Bertschy wrote:
> Hello,
>
> Cygwin version: 1.5.12
> Windows XP Professional: Ver 5.1 Build 2600 Service Pack 2
>
> I am trying to use Cygwin's dd command as a post Windows XP install
> command to restore our custom GRUB to the MBR after an unattended
> installation.
> For safety reasons, I would like to restore only the first 446 bytes of
> the MBR to keep the existing partition table.
>
> The command line to use would normally be:
>    dd if=boot.MBR of=/dev/sda bs=446 count=1
> -->    dd: writing '/dev/sda': No space left on device
>          1+0 records out
>          0+0 records in
> (I also tried with bs=512 and I get the same output)
>
> After reading:
> http://sourceware.org/ml/cygwin/2001-01/msg00193.html
> I decided to try the following:
>    mount -s -b -f //./physicaldrive0 /dev/hd00
>    dd if=boot.MBR of=/dev/hd00 bs=446 count=1
> -->   dd: opening '/dev/hd00': Invalid argument
> (even if I change the device /dev/xxx name, I get the same output)
>
> I even tried directly:
>    dd if=boot.MBR of=//./physicaldrive0 bs=446 count=1
> -->   dd: opening '//./physicaldrive0': Invalid argument
>
> After so many unefficient tries, I decided to read from it, just to see:
>    dd if=//./physicaldrive0 bs=446 count=1
> -->   dd: reading '//./physicaldrive0': Is a directory
>          0+0 records out
>          0+0 records in
>
> So here is the:
>    QUESTION1: Does anyone know how to write into MBR from Windows XP
> using Cygwin's dd ?
>    QUESTION2: I am doing somathing wrong since dd sees
> //./physicaldrive0 as a directory ?
>
> Any help would be appreciated.

Using /dev/sda should work.

-- Cliff

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