[nflug] Disk Image/Restore

Cyber Source peter at thecybersource.com
Wed Jul 26 09:23:16 EDT 2006


Jonathan Skulski wrote:
> On 7/25/06, Cyber Source <peter at thecybersource.com> wrote:
>> >> If we say, put xp on a
>> >> drive that previously had grub on the mbr, we could ghost, dd, tar
>> >> the xp copy onto the drive and then it would fail to boot UNTIL we
>> >> blank the mbr.
>> >
>> > Huh. I know win* does _something_ to my MBR. Because anytime I've
>> > reinstalled any windows it overwrites it and I have to re-run grub
>> > if I want to get to Linux. But I didn't think that the bios
>> > was smart enough to look beyond the first HD sector for boot
>> > information. So if I did a "dd if=/dev/zero of=/dev/hda bs=512
>> > count=1" to get rid of my MBR and my windows partition is set to
>> > bootable (and its the first partition) I could still boot windows?
>> >
>> > -Josh
>>
>> yes, that command is just blanking the mbr just like fixmbr (xp) and
>> fdisk /mbr (dos/98)
>
> Well Josh's question was whether or not blanking the mbr would allow
> win98/xp to boot. Which it does not. I just did a
>
> $ dd if=/dev/sda of=mbr.txt count=1 bs=512
>
> and it was definately was not all zeros (hexdump)
> then i tried a
>
> $ dd if=/dev/zero of=/dev/sda count=1 bs=512
>
> and it didn't boot.
>
> Conclusive proof that:
> -  Windows XP definately needs some sort of instruction in the mbr
> -  fdisk /mbr != dev if=/dev/zero of=/dev/sda count=1 bs=512
>
>
> jsk
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If you were to completely write zeros to the entire drive, then copy in 
your 98 or xp, you would not have to blank the mbr, it would just fire 
up. We've only done this stuff a thousand times around here. What I do 
know, is that it doesn't hurt to run either fixmbr or fdisk /mbr to make 
sure that the previous mbr is not an issue with the new copy.
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