1. Etherboot

Currently there seem to be two different packages for installing a disk-less PC-based UNIX station.

1. On sunsite in pub/linux/system/Linux-boot/netboot-nfs.tar.gz is a package that contains code for patching a 1.2.x Linux kernel to boot from an NFS mounted file-system and to accept an NFS mounted swap file. This package also comes with code for making your own BOOT-prom. Unfortunately, the BOOT-prom code suffers from two major drawbacks.
2. 1. Currently, only Western Digital and SMC Ethernet cards are supported.
   2. You need to have a DOS based 16bit C compiler and assembly code development system for making the BOOT-prom images. (for your convenience, the original kernel patches from this package are found in the directory `netboot-0.x'; please copy the entire package from sunsite, if you need more information on it. I did not write any of the files in this directory, so please refer to the respective copyright information in that directory)
3. FreeBSD comes with its own code for booting disk-less UNIX PC's. This code supports a wide variety of popular Ethernet cards (Western Digital, SMC, NE1000, NE2000, 3COM 3c503, 3COM 3c509). Actually, the code does auto-detection, so you can even have one BOOT-prom image for different cards (although, EPROM size is a limiting factor; if you want to support all different cards with the same BOOT-prom image you will probably have to remove some of the more advanced features of the code). Besides, the code can be compiled in an 32bit environment, using standard GCC. Obviously, this package does not directly support Linux.
4. • FreeBSD uses a different kind of Makefile, thus Linux/GNUmake do not know what to do with this code. (I have been told, that there is a `pmake' for Linux now; I did not know about this when I ported the code, so I had to convert the Makefile manually)
   • The package assumes that GCC outputs FreeBSD-style aout-files.
   • Not surprisingly, the code does not know how to load a Linux kernel image; let alone, how to pass a command line to the linux kernel. (for your convenience, I copied a part of the current FreeBSD source tree into the directory `netboot-freebsd'. Please consult these files for copyright information; you can download the complete FreeBSD source tree from quite a lot of FTP servers, so please use Archie for finding the one nearest to you)

Since both Western Digital and SMC Ethernet cards are a lot more expensive then NE2000 cards (you can get the latter for as little as $10 if you do not mind buying a used one), I was looking into how to obtain a BOOT-prom for an NE2000 card. For lack of an DOS development system, I decided to go with the FreeBSD code.

In the directory `patches', you can find the changes that I had to make in order to get the package support my system. You need to apply two patches to the freebsd-code:

  patch -p0 <netboot-freebsd-compiles-with-linux.patch
  patch -p0 <netboot-freebsd-loads-linux-kernel.patch

(This directory also contains a modified set of patches for patching 1.3.x kernels; as the patch file is based on the code in `netboot-0.x/lx1.2.2-patch', please consult that directory for copyright information!)

If you rather want to try standard settings, you should have a look at the files in the directory `binaries'. I pre-compiled both *.com and *.rom files for all supported ethernet cards. All images will fit in a 16KB EPROM. I could only test the NE2000 code, but I expect that for the majority of users the other files will probably work `out-of-the-box', too. Even if you want to try these images, please read on first, so you know what to do with the files!

If you want to compile your own code, you should edit netboot-freebsd/Makefile or netboot-freebsd/Makefile.linux and make the BOOT-prom images (specify Makefile.linux as your makefile if you compile under Linux).

I never tried building BOOT-prom images in an a.out environment (neither did I try compiling under FreeBSD), but I have been told that there are some old versions of `objdump' that might cause problems. So, if you are stuck with extracting the text and data segment from the compiled binaries, you should either try to update to a newer release of `objdump' or -- preferably -- compile the code in an ELF environment.

Please note, that the BOOT-prom images still support loading FreeBSD, so if you ever decide switching from Linux to FreeBSD you do not have to burn a new EPROM.

Apart from the FreeBSD file format, the BOOT-prom auto-detects Linux kernels and `tagged files'; the latter is the format that is prefered by the netboot-0.x code. If you want to use this format, you need the utilities that come with the netboot-0.x package. For your convenience I copied them into the directory `netboot-0.x' (please note, that I did not write any of the files in that directory, so please refer to the Copyright information that comes with those files).

After calling `make' you will have both a *.com and a *.rom file for your Ethernet card. The *.rom file is exactly 16kB long (please check, that the total size of text segment plus data segment does not exceed 16kB; the sizes are displayed during compilation) and needs to be put into the EPROM. The *.com file can be used for testing the code before burning an EPROM. You should load the *.com file from a boot-disk. I noticed that having other drivers or newer versions of DOS loaded before calling the *.com file can cause serious problems, thus I suggest you format a new DOS disk with system files (format a: /s) and then rename *.com into command.com when you copy it onto the disk (you could also specify the original name as your SHELL= in config.sys).

You will now have to setup your server to provide the necessary services for the disk-less workstation. The following instructions should get you started:

(These instructions assume, that you do *not* use the `tagged file format' that is used by the `netboot-0.x' package; if you prefer to use that format instead, you might want to have a look at ftp://ftp.ix.de/pub/ix/linux/iX-Terminal)

• The server has to provide the disk-less workstation with its IP address, which is queried using the bootp-protocol; thus you will have to install a bootp-demon, activate it in /etc/services and /etc/inetd.conf and supply an entry in /etc/bootptab; if you want to change to a subdirectory before starting the bootp-demon (see below), you will have to put the configuration file into <subdirectory>/etc/bootptab. (if you are on a local sub-net that is not directly connected to the Internet, you can for instance use the IP addresses 192.168.x.y, otherwise please ask either your network administrator or your Internet service provider for your own IP address(es))
• The BOOT-prom code loads a configuration file from either the file given in the BOOTP record (that is the file given in the bf= field), or `cfg.<IP-number>', or `/tftpboot/cfg.<IP-number>'. You will have to setup a tftp-demon for this (it has to be activated in /etc/services and /etc/inetd.conf). Make sure the configuration files are world-readable. For security reasons you might want to consider, whether you can chroot to a subdirectory before starting the tftp-demon (in this case, the demon should probably be compiled statically and you will have to supply a `lib' directory that contains the startup code (such as `ld-linux.so.1'); you might also have to install `libc.so.x') If you do change to a subdirectory for the tftp-demon, you should do the same thing for the bootp-demon (beware! the bootp- demon will return a filename for the kernel file, only if this file is visible to the demon!) The configuration file should set the host-name, the name of the kernel image (in case you did not use bootp in order to set a kernel file name), the path for the root file-system, and any command line parameters that need to be passed to the kernel; I used the following file (your mileage is likely to vary!):

  ---

      hostname appendix.uni-muenster.de
      kernel vmlinuz
      rootfs 192.168.0.1:/usr/boot/root/appendix
      linuxcmd sbpcd=0x230,SoundBlaster
  

  ---

  Press `help' at the boot-prompt for a list of the possible commands. Configuration files must not be longer than 512 bytes. If you do not supply a configuration file, you could instead have a `tagged' kernel image loaded by TFTP; the BOOT-prom will autodetect, whether it reads a configuration file or a `tagged' kernel image!
• After loading the configuration file, the BOOT-prom code attempts to mount the root file system, where it looks for the kernel image (if you used `tagged files', the kernel will be loaded by TFTP instead of NFS!). So please configure both your mount demon and your nfs demon properly. (You might have to restart these demons after changing their configuration files; you could also consider sending the inet-demon a '-HUP' signal, if you want it to reread /etc/inetd.conf) The BOOT-prom will then load the kernel image from the root file system and try to auto-detect, if this is a FreeBSD or a (compressed) Linux kernel. If it is a Linux kernel, the root file system is unmounted, a Linux command line is constructed and the kernel is started; if you applied the patches in either `netboot-0.x/lx1.2.2-patch' or `patches/lx1.3.15-patch' to your kernel, the kernel will then try to remount its root file system.
• For mounting the root file system, the kernel will probably have to use RARP first. In order for this to be successful, your server will have to have the appropriate RARP table entries (c.f. man rarp for further information; putting `/sbin/rarp -s 192.168.0.3 00:00:1B:38:F9:50' in one of my /etc/rc.d/rc... files worked for me).
• From here on, booting continues as usual.

Good luck and enjoy using your new disk-less workstation

Markus (gutschk AT math PERIOD uni-muenster PERIOD de)