That sounds sensible, but you may be a bit tight on memory.  I think
you'll find that a machine that does essentially nothing needs fairly
little memory (64 MB might be ok).  So I'd set up dom0 with perhaps
128, a domU (unpriviledged domain - it's not a subdomain of domain0)
with 64 for kdc, and a domU with more for other stuff.

You may well want ssh access to dom0, or not.   You mentioned ssh in a
domU, so that raises the issue of whether you mean a general shell
server.

xen is pretty easy to set up, if you don't hate grub so much you
become nonfucntional.  The howto is pretty reasonable, but you may
want to move where the kernels are.  Here's my grub config:

# Configure serial port to use as console. Ignore if you'll use VGA only
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
# Let the user select which console to use (serial or VGA), default
# to serial after 10s
terminal --timeout=10 serial console
# Grub config file for NetBSD/xen. Copy as /grub/menu.lst and run
# grub-install /dev/rwd0d (assuming your boot device is wd0).
default=2
fallback=0
# boot after 10s the default entry if the user didn't hit keyboard
timeout=10
# use vga
terminal console
# Load the NetBSD bootloader, letting it load the NetBSD/i386 kernel.
title NetBSD chain
  root        (hd0,0)
  chainloader +1
# Regular NetBSD - does not get boot options
title NetBSD 2.0
  root (hd0,a)
  kernel --type=netbsd /netbsd-GENERIC.gz
# Xen/NetBSD with 384 MB
title Xen 2.0 / NetBSD (hda0, vga)
  root(hd0,0)
  kernel (hd0,a)/xen.gz dom0_mem=393216
  module (hd0,a)/netbsd-XEN0.gz root=/dev/hda1 ro console=pc
title Xen 2.0 / NetBSD.ok (hda0, vga)
  root(hd0,0)
  kernel (hd0,a)/xen.gz dom0_mem=393216
  module (hd0,a)/netbsd-XEN0.ok.gz root=/dev/hda1 ro console=pc
## end of grub config file.

and what's in /:

-rwxr-xr-x  1 root  wheel  8432831 Aug 31 19:35 netbsd
-rw-r--r--  1 gdt   wheel  3965871 Aug 31 10:51 netbsd-GENERIC.gz
-rw-r--r--  1 gdt   wheel  3966100 Aug 30 09:52 netbsd-GENERIC.ok.gz
-r--r--r--  1 gdt   wheel  1668996 Aug 31 10:53 netbsd-INSTALL_XENU.gz
-r--r--r--  1 gdt   wheel  1668188 Aug 30 14:15 netbsd-INSTALL_XENU.ok.gz
-rw-r--r--  1 gdt   wheel  3140211 Aug 31 10:51 netbsd-XEN0.gz
-rw-r--r--  1 gdt   wheel  3140409 Aug 30 14:13 netbsd-XEN0.ok.gz
-rw-r--r--  1 gdt   wheel  1717546 Aug 31 10:51 netbsd-XENU.gz
-rw-r--r--  1 gdt   wheel  1717454 Aug 30 14:13 netbsd-XENU.ok.gz
-rwxr-xr-x  1 root  wheel  8432723 Aug 30 15:17 onetbsd

I just copy the gzipped kernels from releasedir/i386/binary/kernel,
and grub and xen load them gzipped.


Another issue is updating.  I do builds in dom0, and unpack sets on
domU.  The domU kernel really lives in dom0, so my build/install takes
care of that (script to copy it from releasedir to /).


-- 
        Greg Troxel <gdt@ir.bbn.com>