clearing the 4-byte DiskID in the MBR

[Niel Drummond]

greets,

I've been trying to move around my multi-boot system so that all my OS's
are on one HD.. Although I'm having success at doing this, I've come
across a strange symptom described below

http://www.goodells.net/multiboot/partsigs.htm

i.e. my old windows partitions are still appearing in the new
configuration, despite having them hidden within the partition table.

The page above describes a number of solutions: the easiest
one is to wipe the MBR using the usual 'fdisk /mbr', and remove all the
old partitions... However, I'm reluctant to do this, because I have a boot
loader installed in the MBR. All that is needed really, is to remove the
so-called 4-byte DiskID that sits between the boot code and the partition
table in the MBR.

Presumably this could be done with a simple 'dd' command in linux, but I
am quite wary since my previous attempts at fixing boot sectors with dd
has failed, and failing with the MBR might cause quite a problem. Is there
an editor for the MBR about, or a simpler way of doing this ?

regards,

- n

 

[Peter]

I've been trying to move around my multi-boot system so that all my OS's

are on one HD.. Although I'm having success at doing this, I've come
across a strange symptom described below

http://www.goodells.net/multiboot/partsigs.htm

i.e. my old windows partitions are still appearing in the new
configuration, despite having them hidden within the partition table.

I assume that happens with Win2K and not XP (according to supplied doc)?
Clearing DiskID would cause Windows 2000 to regenerate DiskID and reassign
letters for other partitions (hidden or not). You would have to mark those
partitions as non-Windows-recognizable to achieve your goal. Can any boot
manager do that? I doubt.

 

[Zvi Netiv]

greets,

I've been trying to move around my multi-boot system so that all my OS's
are on one HD.. Although I'm having success at doing this, I've come
across a strange symptom described below

http://www.goodells.net/multiboot/partsigs.htm

i.e. my old windows partitions are still appearing in the new
configuration, despite having them hidden within the partition table.

The page above describes a number of solutions: the easiest
one is to wipe the MBR using the usual 'fdisk /mbr', and remove all the
old partitions... However, I'm reluctant to do this, because I have a boot
loader installed in the MBR. All that is needed really, is to remove the
so-called 4-byte DiskID that sits between the boot code and the partition
table in the MBR.

Presumably this could be done with a simple 'dd' command in linux, but I
am quite wary since my previous attempts at fixing boot sectors with dd
has failed, and failing with the MBR might cause quite a problem. Is there
an editor for the MBR about, or a simpler way of doing this ?

Any disk sector editor will do that. The question is if you know the offset of
the diskID for your particular boot manager. Its offset differs in Windows 9x
and W2K/XP style MBR.

Regards

 

[Joep]

greets,

I've been trying to move around my multi-boot system so that all my OS's
are on one HD.. Although I'm having success at doing this, I've come
across a strange symptom described below

http://www.goodells.net/multiboot/partsigs.htm

i.e. my old windows partitions are still appearing in the new
configuration, despite having them hidden within the partition table.

The page above describes a number of solutions: the easiest
one is to wipe the MBR using the usual 'fdisk /mbr', and remove all the
old partitions... However, I'm reluctant to do this, because I have a boot
loader installed in the MBR. All that is needed really, is to remove the
so-called 4-byte DiskID that sits between the boot code and the partition
table in the MBR.

Presumably this could be done with a simple 'dd' command in linux, but I
am quite wary since my previous attempts at fixing boot sectors with dd
has failed, and failing with the MBR might cause quite a problem. Is there
an editor for the MBR about, or a simpler way of doing this ?

regards,

MBRtool (free) from www.diydatarecovery.nl has an option for that.

 

[Niel Drummond]

MBRtool (free) from www.diydatarecovery.nl has an option for that.

thanks, problem solved without a hitch ;-)

The DiskID or 'Volume ID' as MBRtool puts it, is located at an offset of
440 bytes, is 4 bytes long, and is only relevant to win2K / XP / NT.
There is additional documentation in the MBRTool manual, save to say that
different configurations handle the DiskID differently.

Also note, contrary to the article I posted earlier, with Win2K there is
no need to remove the old partitions -- I temporarily marked them with a
non-windows system id, which seemed to work fine.

regards

- n

 

[Irwin]

What do you mean "still appearing in the new configuration"? Where are
they appearing? In Windows explorer? In the boot menu? If in explorer
even when hidden, that is strange. If in boot menu, you might need to
edit boot.ini since it doesn't know that you hid them.