grub2, pxe, and default boot

[Mahlon E. Smith]

Hey all!  New to the list, and fairly new to Grub2.

I've got about 400+ machines as part of a farm.  They are re-imaged
routinely on demand, each image a different preset for the role it needs
to play (even swapping OS at times.)

Traditionally, we used pxelinux to image this stuff remotely.  I really,
really would prefer to use Grub2 for this, but I've run into a small
problem that I'm hoping the list here can lend a hand with.

The machines are set to network boot as a default.  I'd like to keep
this behavior, and let the timeout fallthrough to the primary hard
drive.  (This way, I can use tftp-hpa to rewrite read requests for
'grubenv' to get per-machine environmental vars, and remote-control the
imaging. That part of this process is working great.)

It looks like I can accomplish this via:

    set root=(hd0,1)
    chainloader +1
    boot


The problem is that there aren't any drives loaded by default from the
(pxe) environment.

    sh:grub> ls
    (pxe)


I discovered that I could 'insmod biosdisk', and lo-and-behold get my
hd* nodes (woo!):

    sh:grub> insmod ext2
    sh:grub> insmod biosdisk
    sh:grub> ls
    (hd0) (fd0) (pxe)


However, I can't actually -use- hd0 for anything.  I'm not sure why.
I'm guessing it has something to do with what filesystem it thinks hd0
is:

    sh:grub> ls -lh
    Device hd0: Filesystem type pxefs    <---- uh oh
    Device fd0: Unknown filesystem
    Device pxe: Filesystem type pxefs

    sh:grub> chainloader (hd0,1)+1
    error: no such partition


... and here's where my diagnostic abilities stop.  :)

Can anyone suggest other things to try, reasons why this might be
happening, or other ways to achieve my goal?  Could this just be a bug?

All input welcome and appreciated.

--
Mahlon E. Smith  
http://www.martini.nu/contact.html