perplexing installation error

[Greg Troxel <gdt%ir.bbn.com@localhost>]

I have a (vanilla P4 intel mobo) machine running current from last
week, and up to date xentools and xenkernel, booting into dom0 just
fine.

I am trying to install a domU in a 16G file, created with dd and
/dev/zero sparsely (wrote last k or so, rest is a hole).

The domU boots the -current install iso, and correctly figures out
that the disk is 16G.  When it starts to write to the disk, it fails with:


       Status: Command failed
      Command: disklabel -w -r -f /tmp/disktab xbd0 '[redacted].ir.bbn.com'
       Hit enter to continue
  
--------------------------------------------------------------------------------
  disklabel: can't read filecore boot block: No such file or directory

Do I need to make a disklabel first?  I would think netbsd could
install to a totally blank disk.    I will read disklabel sources, but
would appreciate any clues.



my xen config file (i figured out that disk 0 comes last):

#  -*- mode: python; -*-

#kernel = "/netbsd-XENU.gz"
kernel = "/netbsd-INSTALL_XENU.gz"

# Memory allocation (in megabytes) for the new domain.
memory = 256

# A handy name for your new domain. This will appear in 'xm list',
# and you can use this as parameters for xm in place of the domain number.
name = "[redacted]"

# Which CPU to start domain on (only relevant for SMP hardware)
cpu = -1   # leave to Xen to pick

vif = [ 'mac=[redacted], bridge=bridge0' ]

disk = [ 'file:/usr/obj/auto-current/releasedir/i386/installation/cdrom/netbsd-i
386.iso,cd0a,r', 'file:/n0/xen/[redacted]-wd0,wd0d,w' ]

# Set root device. This one does matter for NetBSD.
root = "/dev/wd0d"
# extra parameters passed to the kernel
#extra = ""

#autorestart = True