bcdedit - stampdisk (parameter) External links Options

[joakim]

The bcdedit.exe tool has lots of parameters and many of them are well documented.

One parameter that I have not seen described anywhere, except on 1 line in the documentation, is STAMPDISK.

It is supposed to sign raw disk when booting winpe.

I have not been able to set this one to any bcd entry yet.

By stringdumping the newer version of bcdedit.exe, I suspect the right usage should be STAMPDISKS and not STAMPDISK.

Have anybody been able to load raw disk images to ram and boot from it, using the new OS? All my tests end with the famous ...7B.

Does anybody know how this STAMPDISKS/STAMPDISK correlates and works with the device specific options about ramdisk?

Btw, I also tried booting winpe(7) with a nested vhd inside a rawdisk mapped to ram with grub4dos. It crashed with 7B halfway into the bootprocess (not very surprising though). The interesting part here is that the booting started and executed winload.exe from such a nested vhd-setup.

Joakim

[was_jaclaz]

The only references I could find was for STAMPDISK (without the S).
http://download.microsoft.com/download/9/c...Dedit_reff.docx

STAMPDISK Boolean Enables stamping of RAW disks during a WinPE boot.

Available only on Windows Server 2008 Beta 3 and later.

http://www.ads-training.com/Lists/The%20Ac...CDedit_reff.doc

It apparently allows "stamping" a disk signature on a RAW device (i.e. and unpartitioned one) but I am completely failing to understand what would be a practical use of it.

jaclaz

[joakim]

That is the doc I was referring to, and the only place I have ever seen it mentioned, except inside bcdedit.exe itself.

I am sure it is there for a reason, and since it clearly is for winpe usage, I would be interested to know what excactly for...

Joakim

[was_jaclaz]

I am sure it is there for a reason, and since it clearly is for winpe usage, I would be interested to know what excactly for...

Yep.
But my question was, if I may insist, a bit more subtle :
Let's assume that this, as per (very scarce) docs, allows the BOOTMGR to write a disk signature on a RAW disk, WHAT would "writing a disk signature on a RAW disk" be useful for?



jaclaz

[joakim]

Let's assume that this, as per (very scarce) docs, allows the BOOTMGR to write a disk signature on a RAW disk, WHAT would "writing a disk signature on a RAW disk" be useful for?

Exactly.

If RAW means unpartitioned and unformatted disks, it makes no sense as bootmgr cannot partition anyway, and the tools available later when winpe has fully booted, will do the signing if necessary. Ie, I guess it's meant to have a purpose in the early bootprocess. My initial guess was ramdisk usage, but not sure. It also states which OS's that makes use of it... And by coincidence, that is those capable of native boot vhd (if beta 3 is mostly the same as R2).

Any guesses?

Joakim

[was_jaclaz]

Yes, the only other "reference" if anything in a PowerPoint file can be defined such is here:
http://209.85.129.132/search?q=cache:RMMSG...mpdisk&cd=3
http://download.microsoft.com/download/5/b...CPA051_WH06.ppt

Deployment Guidelines
Identifying disks
Windows Boot Environment uses disk signatures to identify partitions on disks
Avoids ambiguity of firmware enumeration dependencies
Always ensure a unique disk signature is present on disks
A special consideration to make for disk duplication
Special cases
Special designation for the boot partition
For un-partitioned disks, boot loader will not stamp disk signature
User must partition disk
A reboot may be necessary

I guess that RAW in this context means any disk that has not MBR "magic bytes" signature 55AA and partition table values.

I really cannot imagine an use for a disk signature on an "empty" disk (since BOOTMGR in itself cannot partition/format it.

jaclaz

[joakim]

I guess that RAW in this context means any disk that has not MBR "magic bytes" signature 55AA and partition table values.

What I think it refers to, is the 4 bytes at offset 440 in mbr.

But that does not solve anything.

And it makes no sense to have bootmgr write a signature as part of a repair/recovery process either, as the more advanced tools will become available when winpe is booted.

Joakim

[was_jaclaz]

What I think it refers to, is the 4 bytes at offset 440 in mbr.

Yep, that's the disk signature, apart from NT based systems, which, if a disk signature is not present do force one when mounting the disk, all other operating systems do not use it.

The only occasion when something like this would be useful would be to force a disk signature on a disk that is already partitioned/formatted under another OS, say DOS or Linux and has 00 00 00 00 as signature.
But such a disk is not actually RAW as the reference seems to hint.
Unless it means with an unknown filesystem, say for example reiserFS or Ext2/Ext3FS for which there is not a filesystem driver in the early part of booting.
In which case it would be a way to "tag" a disk even if it's parititoning/formatting is UNKNOWN (but which cannot be defined "RAW").

jaclaz

[joakim]

And if so is its function, it does by definition not make any sense, as it is to be set on winpe entries in the bcd (which of course is not nix based anyway and does not have drivers for such filesystem).

This is annoying!

[karyonix]

Maybe useful for Windows Installation.
Boot loader can read drive 0x80's signature, drive 0x81's signature, ...
Windows can use signatures to identify which drive is 0x80, which drive is 0x81, ...
Windows Setup will install boot manager to drive 0x80 to make it bootable.

If you have two RAW harddisks without signature and boot Windows Setup from DVD.
Windows can see two drive but don't know which one is 0x80. Setup may guess wrong and install boot manager to second harddrive which BIOS will not load at startup.