xref: /src/usr.sbin/ndbootd/README

README for ndbootd-0.1

Copyright (c) 2001 Matthew Fredette.  All rights reserved.

See the file COPYING for no-warranty and distribution terms.

ndbootd is a daemon that serves Sun's old Network Disk (ND) protocol.
This protocol was designed by Sun before they designed NFS.  ND simply
makes the raw blocks of a disk available to network clients.  Contrast
this with the true namespace and file abstractions that NFS provides.

The only reason you're likely to encounter ND nowadays is if you have
an old Sun-2 machine, like the 2/120 or 2/50.  The Sun-2 PROMs can
only use ND to boot over the network.  (Later, the Sun-3 PROMs would
use RARP and TFTP to boot over the network.)

ndbootd is a very simple ND server that only supports client reads.

usage: ndbootd [OPTIONS] BOOT1-BIN
where OPTIONS are:
  -s, --boot2 { BOOT2-BIN | DIR }
                          find a second-stage boot program in the file
                          BOOT2-BIN or in the directory DIR
  -i, --interface NAME    use interface NAME
  -w, --window-size COUNT 
                          send at most COUNT unacknowledged packets [default=6]
  -d, --debug             set debug mode

ndbootd exports a disk that the clients consider to be /dev/ndp0 (ND
public unit zero).  The disk is available to any client listed in
/etc/ethers (Sun-2 PROMs don't do RARP, but they do learn their IP
address from the first ND response they receive from the server.)

BOOT1-BIN is a file containing the mandatory first-stage network boot
program.  The layout of the exported disk is:

block 0: normally a Sun disklabel (but ignored by the PROM)
blocks 1-15: the first-stage network boot program

With the --boot2 option, ndbootd will also make a second-stage network
boot program available to clients.  When --boot2 is used with a
filename BOOT2-BIN, that file is the second-stage network boot program
to be served to all clients.

When --boot2 is used with a directory name DIR, ndbootd finds a
client's second-stage network boot program by turning its IP address
into a filename in that directory, in the same manner later Sun-3
PROMs do when TFTPing (i.e., if a client has IP address 192.168.1.10,
ndbootd expects to find DIR/C0A8010A.SUN2).  The expected use of
--boot2 is with the /tftpboot directory, making ndbootd a functional
replacement for tftp when used with an ND-aware first-stage boot
program.

Any second-stage network boot program always begins at block 16 of the
exported disk, regardless of the length of the first-stage network
boot program.

Whether or not there is a second-stage network boot program, the
exported disk appears to have infinite length.  The content of all
blocks not used by the first- or second-stage network boot programs is
undefined.

All first- and second-stage network boot programs must have had their
exec headers stripped off.

Normally, ndbootd listens on the first up and running IP interface it
finds.  Use the --interface option to give a specific interface.

One parameter of the ND protocol is a sort of window size.  This is
the number of 1-kilobyte packets that can be transmitted before
waiting for an acknowledgement.  To change this from the default 6,
use the --window-size option.

When debug support is compiled in (it is by default), the --debug
option turns on debugging.

ndbootd has only been compiled and tested under NetBSD with BPF
support, although there is a fair autoconf framework, and the raw
interface support is broken out, which should allow for reasonable
porting.

Note that ndbootd was developed specifically to help me to boot my
experimental NetBSD port on my Sun-2/120.  In this scenario, the
first-stage network boot (bootyy) continues to use ND to load in the
second-stage boot program (netboot), which can do a full
RARP/bootparams/NFS boot.  (If the program netboot ever fit in 16
blocks, we could eliminate bootyy, but this is unlikely.)

(Aside: it is unusual for a network boot to have two stages of boot
programs before the kernel; this is normally only done on real disks.
But to the Sun-2 PROMs, /dev/ndp0 is just like a real disk in that it
provides no EOF condition (like a tape boot gets, or like the Sun-3
TFTP method gets), so it only loads a fixed number of blocks.)

Whether ndbootd can be used to netboot SunOS on a Sun-2 is unknown, but
the hope is that you can use the SunOS-provided sun2.bb file as the
first-stage boot program, not use any --boot2 option, and ndbootd will
perform as the SunOS ndbootd did.

To configure ndbootd for compiling, run the 'configure' script,
followed by make.  To report bugs in compiling or using ndbootd, email
fredette@alum.mit.edu, and please include as much information as you
can about what you're trying to do and what goes wrong.  I don't have
much time to do support, but I'll try.