PXE boot seems to use incorrect NFS root

[William Rose]

Hi,

I'm trying to set up my gateway machine to offer a FreeBSD live boot to
PXE capable clients, namely my Compaq TabletPC.  The TabletPC has a
Intel Pro 100/M, which seems to work fine (after I patched the if_fxp.c
file with the new device id).  I have working TFTP, DHCP and NFS servers
(as far as I can tell).  I have a generic kernel plus options BOOTP,
BOOTP_NFSROOT, BOOTP_NFSV3 and BOOTP_COMPAT.

I have created a new diskless root manually -- not by using the
technique suggested in the article on freebsd.org.  But I've fixed
/etc/fstab to reflect the NFS mounted root.  I'm not trying to run X
(yet).  This is more to get a booting FreeBSD on a system that does not
have a CD-ROM, floppy or normal keyboard (USB keyboard and mouse only). 
So I tend to run into problems as I can't get usbd to run, and this is
why I have only been able to do very limited debugging.

What happens is that the PXE code runs, gets an IP address and loads the
pxeboot program via TFTP.  This is then able to mount the NFS volume I
specify in the root-path option in /etc/dhcpd.conf.  It loads the kernel
and modules, boots, detects devices (including my NIC), and runs DHCP to
get an IP again and the root-path so it can mount the NFS root.

It fails shortly thereafter:

[snipped up to DHCP Ack with option root-path]
  Adjusted interface fxp0
  Shutdown interface faith0
* Mounting root from nfs:192.168.0.1:/pxeboot
  no such device 'pxeboot'
  setrootbyname failed
  NFS ROOT: 192.168.123.1:/pxeboot
  Interface fxp0 IP-Address 192.168.0.7 Broadcast 192.168.0.255
[blah blah blah]
  fstab: /etc/fstab:0: No such file or directory
[blah blah blah]

... and drops to a shell I can't use (keyboard has stopped working now).
The value on the line marked by (*) seems to be coming from the
/etc/fstab on the exported /pxeboot root fs I have created (not option
root-path as I expected).

Is this all my own silly fault for not using the approved technique? 
What have I left out?  I can send snippets of dhcpd or other
configuration files if helpful.

cheers,
Will