Add kernel configuration via bootp to kernel.  You can see more options
in LINT, these are a good set

  # Kernel BOOTP support  
  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 root
  options         BOOTP_COMPAT    # Workaround for broken bootp daemons.

Setup Bootp server or DHCP server, here is an example entry for /etc/bootptab
refer to the man page bootpd for more information.

       .default:\
             :sm=255.255.255.0:\
             :gw=your.gateway.ip:\
             :hn:ht=ether:vm=rfc1048:\
             :rp="rootfs.ip:/rootfs/path":\
             :T128="swapfs.ip:/swapfs/path":\
             :T129=swapsize:\
             :T130="root,mount,options":\
             :T131="swap,mount,options":\
             :ra=255.255.255.255:
       client01:bf="kernel":ha=00400530d6d9:tc=.default:
 
Enable bootpd in inetd by uncommented the "bootps" line.

Setup tftpd, copy your kernel into you tftpboot directory.  Note you should
make the kernel accessible in both the rootfs and the tftpboot area.

Enable tftpd by uncommenting tftp in /etc/inetd.conf.  If you give the
full kernel path then remove the /tftpboot directory option in inetd.conf.
Again for more information look at man tftpd.

Send a SIGHUP to the inetd process.

Make sure you export the rootfs, in /etc/exports and SIGHUP mountd if
needed.  Refer to the man page mountd for more information.

The swapfile if specified will need to be created.  Just do a "dd" of
/dev/zero for the size you want into the path specified in the bootptab
with the IP address appended for example:
	/usr/exports/swap/swap.192.168.1.1

Now you should be ready to boot diskless.

Note there are some usefull boot time configuration file in /etc/rc.diskless.

Note2 NFS mount of root was broken in current it has been fixed.