IMPORTANT NOTE:

As of Feb. 11, 2002 (and indeed, for quite some time before that),
the /etc/rc.diskless{1,2} scripts support a slightly different
diskless boot process than the one documented in the rest of
this file (which is 3 years old).

I am not deleting the information below because it contains some
useful background information on diskless operation, but for the
actual details you should look at /etc/rc.diskless1, /etc/rc.diskless2,
and the /usr/share/examples/diskless/clone_root script which can
be useful to set up clients and server for diskless boot.

--- $FreeBSD: head/share/examples/diskless/README.BOOTP 240518 2012-09-14 21:28:56Z eadler $ ---
------------------------------------------------------------------------

		        BOOTP configuration mechanism

			    Matthew Dillon
			    dillon@backplane.com

    BOOTP kernels automatically configure the machine's IP address, netmask,
    optional NFS based swap, and NFS based root mount.  The NFS server will
    typically export a shared read-only /, /usr, and /var to any number of
    workstations.  The shared read-only root is typically either the server's
    own root or, if you are more security conscious, a contrived root.

    The key issue with starting up a BOOTP kernel is that you typically want
    to export read-only NFS partitions from the server, yet still be able to
    customize each workstation ( or not ).

    /etc/rc.diskless1 is responsible for doing core mounts and for retargeting
    /conf/ME ( part of the read-only root NFS mount ) to /conf/$IP_OF_CLIENT.
    /etc/rc.conf.local and /etc/rc.local, along with other machine-specific
    configuration files, are typically softlinks to /conf/ME/<filename>.

    In the BOOTP workstation /conf/$IP/rc.conf.local, you must typically
    turn *OFF* most of the system option defaults in /etc/rc.conf as well
    as do additional custom configuration of your environment

    The /usr/src/share/examples/diskless directory contains a typical
    X session / sshd based workstation configuration.  The directories
    involved are HT.DISKLESS/ and 192.157.86.12/. 

    Essentially, the $IP/ directory ( which rc.diskless looks for in
    /conf/$IP/ ) contains all the junk.  The HT.DISKLESS directory exists
    to hold common elements of your custom configuration so you do not have
    to repeat those elements for each workstation.  The example /conf 
    structure included here shows how to create a working sshd setup ( so
    you can sshd into the diskless workstation ), retarget xdm's pid and error
    files to R+W directories if /usr is mounted read-only, and retarget
    syslogd and other programs.  This example is not designed to run out of
    the box and some modifications are required.

    >> NOTE <<  HT.DISKLESS/ttys contains the typical configuration required
    to bring X up at boot time.  Essentially, it runs xdm in the foreground
    with the appropriate arguments rather then a getty on ttyv0.  You must
    run xdm on ttyv0 in order to prevent xdm racing with getty on a virtual
    terminal.  Such a race can cause your keyboard to be directed away from
    the X session, essentially making the session unusable.

    Typically you should start with a clean slate by tar-copying this example
    directory to /conf and then hack on it in /conf rather then in 
    /usr/share/examples/diskless.

				BOOTP CLIENT SETUP

    Here is a typical kernel configuration.  If you have only one ethernet
    interface you do not need to wire BOOTP to a specific interface name.
    BOOTP requires NFS and NFS_ROOT, and our boot scripts require MFS.  If
    your /tmp is *not* a softlink to /var/tmp, the scripts also require NULLFS

# BootP
#
options         BOOTP           # Use BOOTP to obtain IP address/hostname
options         BOOTP_NFSROOT   # NFS mount root filesystem using BOOTP info
options         "BOOTP_NFSV3"   # Use NFS v3 to NFS mount rootoptions
options         BOOTP_COMPAT    # Workaround for broken bootp daemons.
#options         "BOOTP_WIRED_TO=de0"

options         MFS                     # Memory File System
options         NFS                     # Network Filesystem
options         NFS_ROOT		# Nfs can be root
options		NULLFS			# nullfs to map /var/tmp to /tmp

				BOOTP SERVER SETUP

    The BOOTP server must be running on the same logical LAN as the
    BOOTP client(s).  You need to setup two things:

    (1) You need to NFS-export /, /usr, and /var.

    (2) You need to run a BOOTP server.  DHCPD can do this.


    NFS Export:

	Here is an example "/etc/exports" file.

/ -ro -maproot=root: -network 192.157.86.0 -mask 255.255.255.192
/usr -ro -maproot=root: -network 192.157.86.0 -mask 255.255.255.192
/var -ro -maproot=root: -network 192.157.86.0 -mask 255.255.255.192

    In order to be an NFS server, the server must run portmap, mountd,
    nfsd, and rpc.statd.  The standard NFS server options in /etc/rc.conf
    will work ( you should put your overrides in /etc/rc.conf.local on the
    server and not edit the distribution /etc/rc.conf, though ).

    BOOTP Server:

	This configuration file "/etc/dhcpd.conf" example is for 
	the '/usr/ports/net/isc-dhcp' dhcpd port.

	    subnet 192.157.86.0 netmask 255.255.255.192 {
		# range if you want to run the core dhcpd service of
		# dynamic IP assignment, but it is not used with BOOTP 
		# workstations
		range 192.157.86.32 192.157.86.62;

		# misc configuration.
		#
		option routers 192.157.86.2;
		option domain-name-servers 192.157.86.2;

		server-name "apollo.fubar.com";
		option subnet-mask 255.255.255.192;
		option domain-name-servers 192.157.86.2;
		option domain-name "fubar.com";
		option broadcast-address 192.157.86.63;
		option routers 192.157.86.2;
	    }

	    host test1 {
		hardware ethernet 00:a0:c9:d3:38:25;
		fixed-address 192.157.86.11;
		option root-path "192.157.86.2:/";
		option option-128 "192.157.86.2:/images/swap";
	    }

	    host test2 {
	    #    hardware ethernet 00:e0:29:1d:16:09;
		hardware ethernet 00:10:5a:a8:94:0e;
		fixed-address 192.157.86.12;
		option root-path "192.157.86.2:/";
		option option-128 "192.157.86.2:/images/swap";
	    }

    SWAP.  This example includes options to automatically BOOTP configure
    NFS swap on each workstation.  In order to use this capabilities you
    need to NFS-export a swap directory READ+WRITE to the workstations.

    You must then create a swap directory for each workstation you wish to
    assign swap to.  In this example I created a dummy user 'lander' and
    did an NFS export of /images/swap enforcing a UID of 'lander' for
    all accesses.

	apollo:/usr/ports/net# ls -la /images/swap
	total 491786
	drwxr-xr-x  2 root    wheel        512 Dec 28 07:00 .
	drwxr-xr-x  8 root    wheel        512 Jan 20 10:54 ..
	-rw-r--r--  1 lander  wheel   33554432 Dec 23 14:35 swap.192.157.86.11
	-rw-r--r--  1 lander  wheel  335544320 Jan 24 16:55 swap.192.157.86.12
	-rw-r--r--  1 lander  wheel  134217728 Jan 21 17:19 swap.192.157.86.6

    A swap file is best created with dd:

	# create a 32MB swap file for a BOOTP workstation
	dd if=/dev/zero of=swap.IPADDRESS bs=1m count=32

    It is generally a good idea to give your workstations some swap space,
    but not a requirement if they have a lot of memory.