Diskless X Server: a how to guide

Jerry Kendall



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With the help of some friends on the FreeBSD-hackers list, I have been able to create a diskless X terminal. The creation of the X terminal required first creating a diskless system with minimal utilities mounted via NFS. These same steps were used to create 2 separate diskless systems. The first is altair.example.com. A diskless X terminal that I run on my old 386DX-40. It has a 340Meg hard disk but, I did not want to change it. So, it boots from antares.example.com across a Ethernet. The second system is a 486DX2-66. I set up a diskless FreeBSD (complete) that uses no local disk. The server in that case is a Sun 670MP running SunOS™ 4.1.3. The same setup configuration was needed for both.

I am sure that there is stuff that needs to be added to this. Please send me any comments.

1 Creating the boot floppy (On the diskless system)

Since the network boot loaders will not work with some of the TSR's and such that MS-DOS® uses, it is best to create a dedicated boot floppy or, if you can, create an MS-DOS menu that will (via the config.sys/autoexec.bat files) ask what configuration to load when the system starts. The later is the method that I use and it works great. My MS-DOS (6.x) menu is below.

Example 1. config.sys

menuitem=normal, normal
menuitem=unix, unix
normal config.sys stuff

Example 2. autoexec.bat

goto %config%

normal autoexec.bat stuff
goto end

cd \netboot


2 Getting the network boot programs (On the server)

Compile the “net-boot” programs that are located in /usr/src/sys/i386/boot/netboot. You should read the comments at the top of the Makefile. Adjust as required. Make a backup of the original in case something goes wrong. When the build is done, there should be 2 MS-DOS executables, nb8390.com and nb3c509.com. One of these two programs will be what you need to run on the diskless server. It will load the kernel from the boot server. At this point, put both programs on the MS-DOS boot floppy created earlier.

3 Determine which program to run (On the diskless system)

If you know the chipset that your Ethernet adapter uses, this is easy. If you have the NS8390 chipset, or a NS8390 based chipset, use nb8390.com. If you have a 3Com® 509 based chipset, use the nb3C509.com boot program. If you are not sure which you have, try using one, if it says “No adapter found”, try the other. Beyond that, you are pretty much on your own.

4 Booting across the network

Boot the diskless system with out any config.sys/autoexec.bat files. Try running the boot program for your Ethernet adapter.

My Ethernet adapter is running in WD8013 16bit mode so I run nb8390.com

C:> cd \netboot
C:> nb8390

Boot from Network (Y/N) ?  Y

BOOTP/TFTP/NFS bootstrap loader     ESC for menu

Searching for adapter..
WD8013EBT base 0x0300, memory 0x000D8000, addr 00:40:01:43:26:66

Searching for server...

At this point, my diskless system is trying to find a machine to act as a boot server. Make note of the addr line above, you will need this number later. Reset the diskless system and modify your config.sys and autoexec.bat files to do these steps automatically for you. Perhaps in a menu. If you had to run nb3c509.com instead of nb8390.com the output is the same as above. If you got “No adapter found” at the Searching for adapter... message, verify that you did indeed set the compile time defines in the Makefile correctly.

5 Allowing systems to boot across the network (On the server)

Make sure the /etc/inetd.conf file has entries for tftp and bootps. Mine are listed below:

tftp   dgram   udp wait    nobody  /usr/libexec/tftpd  tftpd /tftpboot
# Additions by who ever you are
bootps  dgram  udp  wait  root  /usr/libexec/bootpd bootpd /etc/bootptab

If you have to change the /etc/inetd.conf file, send a HUP signal to inetd(8). To do this, get the process ID of inetd with ps -ax | grep inetd | grep -v grep. Once you have it, send it a HUP signal. Do this by kill -HUP <pid>. This will force inetd to re-read its config file.

Did you remember to note the addr line from the output of the boot loader on the diskless system? Guess what, here is where you need it.

Add an entry to /etc/bootptab (maybe creating the file). It should be laid out identical to this:


The lines are as follows:

altair the diskless systems name without the domain name.
ht=ether the hardware type of “ethernet”.
ha=004001432666 the hardware address (the number noted above).
sm= the subnet mask.
hn tells server to send client's hostname to the client.
ds= tells the client who the domain server is.
ip= tells the client what its IP address is.
gw= tells the client what the default gateway is.
vm=... just leave it there.

Note: Be sure to set up the IP addresses correctly, the addresses above are my own.

Create the directory /tftpboot on the server it will contain the configuration files for the diskless systems that the server will serve. These files will be named cfg.ip where ip is the IP address of the diskless system. The config file for altair is /tftpboot/cfg. The contents is:

hostname altair.example.com

The line hostname altair.example.com simply tells the diskless system what its fully qualified domain name is.

The line rootfs tells the diskless system where its NFS mountable root filesystem is located.

Note: The NFS mounted root filesystem will be mounted read only.

The hierarchy for the diskless system can be re-mounted allowing read-write operations if required.

I use my spare 386DX-40 as a dedicated X terminal.

The hierarchy for altair is:


The actual list of files is:

-r-xr-xr-x  1 root  wheel  779984 Dec 11 23:44 ./kernel
-r-xr-xr-x  1 root    bin  299008 Dec 12 00:22 ./bin/sh
-rw-r--r--  1 root  wheel     499 Dec 15 15:54 ./etc/rc
-rw-r--r--  1 root  wheel    1411 Dec 11 23:19 ./etc/ttys
-rw-r--r--  1 root  wheel     157 Dec 15 15:42 ./etc/hosts
-rw-r--r--  1 root    bin    1569 Dec 15 15:26 ./etc/XF86Config.altair
-r-x------  1 bin     bin  151552 Jun 10  1995 ./sbin/init
-r-xr-xr-x  1 bin     bin  176128 Jun 10  1995 ./sbin/ifconfig
-r-xr-xr-x  1 bin     bin  110592 Jun 10  1995 ./sbin/mount_nfs
-r-xr-xr-x  1 bin     bin  135168 Jun 10  1995 ./sbin/reboot
-r-xr-xr-x  1 root    bin   73728 Dec 13 22:38 ./sbin/mount
-r-xr-xr-x  1 root  wheel    1992 Jun 10  1995 ./dev/MAKEDEV.local
-r-xr-xr-x  1 root  wheel   24419 Jun 10  1995 ./dev/MAKEDEV

If you are not using devfs(5) (which is the default in FreeBSD 5.X), you should make sure that you do not forget to run MAKEDEV all in the dev directory.

My /etc/rc for altair is:

export PATH
# configure the localhost
/sbin/ifconfig lo0
# configure the ethernet card
/sbin/ifconfig ed0 netmask 0xffffff00
# mount the root filesystem via NFS
/sbin/mount antares:/DiskLess/rootfs/altair /
# mount the /usr filesystem via NFS
/sbin/mount antares:/DiskLess/usr /usr
/usr/X11R6/bin/XF86_SVGA -query antares -xf86config /etc/XF86Config.altair > /dev/null 2>&1
# Reboot after X exits
# We blew up....
exit 1

Any comments and all questions welcome.

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