Linux Remote-Boot mini-HOWTO: Configuring Remote-Boot Workstations with Linux, DOS, Windows 95/98 and Windows NT

Marc Vuilleumier Stückelberg, David Clerc

v3.19, February 1999

This document describes how to set up a very robust and secure server-based configuration for a cluster of PCs, allowing each client to choose at boot-time which operating system to run. The key of this configuration is a bootprom based program, which let the user choose at boot time one of several boot images. This configuration is applicable using InCom TCP/IP Bootprom (add-on for most network cards) or any PXE-compliant Boot ROM (ready-to-use in most recent PC with built-in network cards). The most up-to-date version of this document, with hypertext links to downloadable software and other related materials, can be found at the address Linuxdoc-SGML, DVI and PostScript versions are available in the same directory. If you are interested in getting info on further developpments, send an E-mail to

1. Disclaimer and Copyrights

2. What has changed...

3. Introduction

4. The Configuration How-To

5. Remote-Boot Tools Reference Manual

6. Special TFTP Servers

1. Disclaimer and Copyrights

This document and the related software are provided as is to the Linux and Internet community, with no form of warranty. Please note that some operations related in this document may destroy the content of your hard-disk. We assume no liability for any use, correct or not, of this document and of the related software.

You are free to do anything you want with the remote-boot tools as long as you do not make money by selling them or by distributing them with a commercial product. If you want to commercialize a product derived from these tools, please contact the authors first to make a commercial agreement. These remote-boot tools will remain available for free forever, but we may authorize derived commercial tools.

These provisions shall be interpreted under and in accordance with the laws of Switzerland, canton of Geneva. All disputes, defenses, controversies or claims arrising in conncetion with this document and the related software, shall be subject to the exclusive juridiction of the courts of the canton of Geneva, Switzerland.

If you like this program, you can send us a Postcard and/or make a gift to the International Committee of the Red Cross (ICRC) or to the UNICEF.

2. What has changed...

2.1 ...since version 2.x ?

To say it frankly, almost everything. The underlying concepts are the same, but the software part has been completly redesigned to overcome the limitations of previous versions and to make it easier to use. An highlight of the new features :

Is there a program for converting old archives to the new format ?

No, because the internal format is radically different. But you can easily do the conversion by yourself:

  1. Boot an old image (unzip it to your disk)
  2. Remove calls to the old unzipreg utility and replace them by the adequate patch commands (it is very easy, see the detailed instructions below)
  3. Run the new mrzip program to create a new-style disk image

2.2 ...since version 3.0 ?

Version 3.0 was the beta-release. A dozen of sites around the world have tested it during a month and given much of their time to help us finding bugs and to suggest enhancements. Thanks to all of them for their patience, and in particular to Maciek Uhlig, Dick Velders and Jeff Teeters.

A few minor features have been added since 3.01, such as support for diskless Linux boot (by disabling the cache).

Version 3.10 introduced compatibility with Intel's Wired for Management 1.1a NetPC standard. The tools now work with any PXE-compliant boot ROM (as are most on-board boot ROMs) available today. Thanks to InCom GmbH for giving us the PXE bootprom that permitted this developpment. We also succesfully tested the tools with the PXE Boot ROM that I found incidentally in my Dell computer with onboard network card (called LanDesk Service Agent).

Version 3.11 to 3.12 added UNIX server-side tools (a PXE Proxy DHCP server for Solaris and Linux, and an enhanced TFTP server for Linux), as well as detailled informations on server-side setup and the PXE booting process.

Version 3.13 added Advanced Power Management support (PowerOff command).

Version 3.14 added minor enhancements and some corrections. We fixed a problem with the terminal under RedHat 5.1, and another problem in the syntax of the "if" command. We added some features suggested by the Laboratori de Càlcul de la Facultat d'Informàtica de Barcelona (LCFIB) :

Version 3.15 added full VESA support. BpBatch now support several video modes, to accomodate old computers not being able to display 800x600 graphics. A new parameter has been added to InitGraph to specify the video mode, and a list of detected video mode can be retrieved from the new VESA-Modes variable.

Version 3.16 fixes the following bugs:

Version 3.17 adds some minor features and fixes bugs:

Version 3.18 fixes a bug with the IncrUnzip function. Thanks to Gary Pike for its collaboration.

Version 3.19 fixed a bug in the error handling of the delete command on ext2fs, as well as the inappropriate handling of names starting with A: under Linux. The following new features were also added:

Thanks to Ruben Schattevoy for its help and contributions to this release.

3. Introduction

The configuration described here was developped since Summer 1996 at the CUI, University of Geneva. The Computer Science Department uses several servers and a number of PCs, which fall into two classes:

We developped the current configuration with the following aims: These constraints lead us to base our configuration on bootprom tools. We first developped new tools for the excellent TCP/IP Bootprom from InCom GmbH. Now that a standard for preboot execution environments as finally emerged, we ported the tools so that it now also works for any PXE-compliant bootprom. PXE boot roms, also called LanDesk Service Agent, are now distributed with almost all on-board network adapter. For more info on PXE and Intel Wired for Management standard in general, read from

3.1 Boot ROM and Hard-disk

Bootproms exist for quite a long time, but until recently, they were solely used with diskless computers. Since 1996, this How-to has been claiming that bootproms are even more interesting for computers which have a local harddisk, since they allow to take profit of both sides:

Today, we have the pleasure to see that all computer manufacturers have come to the same point and provide boot roms as part of new computer standards.

Note that you can still use the tools described below in an old fashioned way, that is as a simple kernel/ramdisk loader, even for diskless computers. However, we do not encourage this use.

3.2 The Network

The University of Geneva owns a class B domain, subdivided into several subnets. The CUI uses four subnets, among them one is dedicated to students.

Originally, our PCs were concerned about two network protocols: IPX and IP. On the IPX side, we used a single Novell Netware 3 server for sharing software and users files for DOS and Windows. On the IP side, we used a SUN server for sharing software and users partitions for Linux, with NFS.

In our latest configuration, we do not any more use IPX. There is a single Unix server (which could be Linux as well as a SUN), sharing software and user files using NFS for Linux clients and using SMB (NetBIOS) over TCP/IP for Dos and Windows clients. In this way, we have a single home directory used by all operating systems.

3.3 How it Works

  1. When a client PC is turned on, it first performs the traditional system checks before the TCP/IP Bootprom or PXE Boot ROM takes the control.
  2. The bootprom issues a BOOTP/DHCP request in order to get its IP configuration parameters.
  3. If the server knows the PC issuing the request, it will send back a BOOTP/DHCP reply with informations such as the client's IP address, the default gateway, and which bootdisk image to use.
  4. In case of a PXE boot ROM, there might be some more exchanges between the client and the server to determine installation parameters.
  5. The bootprom then downloads the boot image from the server using the TFTP protocol. The boot image happens to be a small program called bpbatch, our boot-time batch file interpreter.
  6. The batch interpreter is started. At this time, it is almost alone in the computer memory. There is no operating system loaded, except the preboot execution environment (offered by the Boot ROM).
  7. The batch interpreter look in the BOOTP/DHCP reply for command-line options, and in particular for the name of the batch to execute.
  8. According to the instructions in the batch file, it will for instance:
    1. Load a national keyboard mapping
    2. Authenticate the user according to a remote server (Unix, Radius or Windows NT)
    3. Let the user choose between the available operating systems
    4. According to the operating system choosen, repartition the hard-disk and quick-format some partitions
    5. Check if an up-to-date compressed image of the selected OS is present at the end of the disk. If not, it download it using TFTP
    6. Uncompress the selected OS to the main partition
    7. If the selected OS is Linux, load a kernel and start it
    8. If the selected OS is DOS or Windows, simply let the computer boot on its fresh new hard-disk
    For DOS and Windows 3.1, we use the freely available Microsoft LanManager for DOS (search the network for the mirror nearest to you; the distribution consists of three files named disk1 to disk4) as SMB client. Microsoft LanManager supports dynamic configuration using DHCP. After logging in, the user is faced to DOS, and can start Windows 3.1 by typing the traditional win command. Note that at this point, DOS and Windows 3.1 appear to be installed locally. For Windows 95 and Windows NT, we also use Microsoft SMB client (called Client for the Microsoft Network), that supports dynamic configuration using DHCP. We reduce network load using Shared LAN Cache, a nice and powerful network-to-disk cache program.
Students computers can be turned off the hard way at any time without risks, since the hard disk is reinitialized at each start.

For "safe" computers (ie. for assistants computers), once the computer has been booted once using the above described system, the boot script simply redirect the boot to the local hard-disk, without cleaning it again. This allow users to leave data on their local hard disk. But whenever the configuration gets corrupted, the user can simply choose from the boot menu in order to have a fresh installation.

3.4 Related non-commercial documentations

This configuration has been successfully reproduced at several places around the world. A few people have written some hints and tricks that complement this How-To. If you did so and that your page is not already referenced in this documentation, please send an e-mail to And if you experience problems while reproducing this configuration, have a look at these pages !

You can also send me your BpBatch script if you want me to include it in the sample scripts collection.

4. The Configuration How-To

First, arrange to have the following two machines within arm's reach:

If you want to test the configuration but you do not yet have a bootprom, you can download the TCP/IP BootProm demo diskette from InCom GmbH at This diskette will make your computer behave like if it had a TCP/IP Bootprom plugged in.

If you already have a Boot ROM, you need to enable it. If you are using Incom TCP/IP Bootprom, you can do that using a special program from your network card manufacturer. If you have a PXE Bootprom, you can do it simply from BIOS setup, by changing the default boot device.

For student computers, we configured the boot on network first, and disabled hard-disk and floppy-disk boot. For assistant computers, we also configured network-boot first, but we allow hard-disk and floppy-disk boot.

4.1 Server-side configuration

On the server, you will need the following services:

  1. A BOOTP/DHCP server
  2. May be a Proxy DHCP server
  3. A TFTP server
Note for PXE Boot ROM users: We found after severals hours of tedious search that PXE Boot ROMs with version before 0.99 do not follow the IP protocol and discard all packets that have the Don't Fragment (DF) flag set. That means, you will have to disable Path MTU Discovery on the server, or the Boot ROM will not see any of its packets. On Solaris, use ndd /dev/ip ip_path_mtu_discovery to see if you have it enabled and ndd -set /dev/ip ip_path_mtu_discovery 0 to disable it. However, this fix only works for non-broadcast packets (ask SUN why...). That means, it will work for TFTP but not for DHCP :-(. Intel has recently fixed this bug, and if you bought your computer after June 1998, you surely have a corrected PXE implementation.

Setting up DHCP

The role of the DHCP server is to give to the client an IP address and to make it load the file named bpbatch.P from the TFTP server. DHCP is a superprotocol over BOOTP. If you are using InCom TCP/IP Bootprom, you may live without DHCP (using an old BOOTP server).

On Windows NT, you will probably use the native DHCP server. If you are using InCom TCP/IP Bootprom, you will have to use a special trick to specify the boot file name (get more info from InCom WWW site). If you are using a PXE Bootrom, you will need a Proxy DHCP server, but no other trick is needed as the boot file name will be provided by the Proxy DHCP server.

On Linux, the best choice is the standard DHCP server from the Internet Software Consortium. If you are using a PXE Bootrom, in addition to the usual options, you will need to add the following ones:

On Solaris, you can either use the Internet Software Consortium DHCP server (available on the Web), or use Solaris DHCP server (available since Solaris 2.5). However, as Solaris DHCP server does not seems to be able to insert a client class identifier in its DHCP offer, you must install a Proxy DHCP server. Morever, this Proxy DHCP server must reside on another computer since Solaris DHCP server locks the DHCP port.

We suggest giving infinite lease time for remote-boot clients. Don't forget that BOOTP/DHCP requests are bounded by subnets. If the client and the server do not reside on the same subnet, you should install a BOOTP/DHCP Relay agent on any computer between the two. For now, just assume that both machines are on the same subnet.

Setting up a Proxy DHCP

The role of the Proxy DHCP server is to overcome limitions of some DHCP servers and to provide PXE specific extensions. A proxy DHCP server only makes sense for a PXE Boot rom.

As BpBatch itself is quite powerfull, you wont need to use any PXE specific DHCP extension (menus, etc.). However, if your DHCP server is not able to show minimal PXE compliance, you will need a Proxy DHCP server or your PXE Boot ROM will not accept to go further.

On Windows NT, you can try to use Intel WfM PDK (available from their web site), but it is not very easy to use. We rather suggest having a Linux machine on the subnet and using our small Proxy DHCP. The major advantage of our Proxy DHCP Server for BpBatch is that our server will let you specify an option 155 vendor tag that will be interpreted by BpBatch as a command line.

On Linux and Solaris, you can run our Proxy DHCP program, that simply takes as argument the TFTP server IP address, boot file name and optional arguments, and does everything for you. If the DHCP port on the server is already requested by another daemon, the proxy DHCP server will run on port 4011. In this case, it is necessary that the other daemon on DHCP port answer a DHCP offer with client class PXEClient so that the PXE client knows that it must try on port 4011.

If you want to understand better PXE extensions to DHCP, there is an extensive description available on Intel WWW site. However, be warned that the documents are quite confusing, as the protocol has been extended to a number of optional stages, in order to allow for a maximal flexibility. The key to understand it is that all what a PXE client needs is a complete enhanced DHCP answer. If it receives only a standard DHCP offer, it will look further until it gets

  1. a client class (T60) set to PXEClient
  2. vendor encapsulated options (T43) (possibly empty, ie. hex ff)
  3. a non-empty boot filename
The PXE specific negociation ends as soon as all these infos are received, but can lead to a very complex process (install server discovery, etc.) if some are missing.

Setting up TFTP

The TFTP server is a very simple file server. In its basic version, TFTP use 512 bytes data blocks, which are quite inefficients. InCom TCP/IP Bootprom and PXE Boot ROMs allow to use larger blocks (1408 bytes), which speeds up transfers a lot. However, this can only work with an enhanced TFTP server.

On Windows NT, we suggest using InCom enhanced TFTP server, available on their web site.

On Linux, you can use our enhanced TFTP server, available at

On Solaris, you should use InCom enhanced TFTP serer, available on the utility disk provided with the TCP/IP Bootprom.

If you prefer using a standard TFTP daemon, remove the P in all boot image name extensions, in order to tell the Bootprom to use only the standard TFTP port (This trick was introduced by InCom GmbH for the TCP/IP Bootprom. We still use it as an easy way to select the default TFTP port with PXE bootproms).

4.2 Client-side configuration

First, we will do set up the part common to all operating systems, ie. the batch-file interpreter. Then, for each operating system, we will go through the following steps:

  1. Setup a stand-alone client
  2. Save its configuration on the server
  3. Test it as a remote-boot client
  4. Adapt it so that it works for any similar client machine
Once this is done, you will be able to setup any supplemental client just by plugging a Boot ROM in it (or buying a Wired for Management ready computer...) and adding one line in the DHCP configuration file.

Our examples assume that you have a hard disk of 1.4 Gb or more. If you have less, reduce the sizes of the partitions, but remember the you need to leave a few hundreds megabytes unallocated (that is, the last partition must not take up to the last cylinder) to leave free room for the special cache partition. Moreover, as the cache always starts at the cylinder following the last allocated cylinder, if you do not use the same total size for all your tests, you will have to download several times the same files (the cache will be automatically cleared).

Never despair. If you can't get it to work, first look in the Troubleshooting section if your problem is not already solved (get the latest version from the Web). Then, take a look in the BpBatch forum. Perhaps someone else had the same troubles as you have, and the answer can be found in the forum. Forum's URL : If it still does not work, think about monitoring network traffic for network related problems (use tcpdump on Linux or snoop on Solaris). If you really cannot get it to work, you can send an E-mail to or If your problem is strictly related with the remote-boot configuration and if we are not overflowed, we will try to solve your problem.

4.3 Setting Up the Boot Process

Get the BpBatch software, either as .zip or as .tar.gz. The executables are available at

The source code (Assembler and C) is also available on request.

In the server /tftpboot directory, put the following three special boot images, which together make our pre-boot batch file interpreter:

Then add an entry in the DHCP configuration file for your client, with the boot file set to "bpbatch.P". Define a vendor option tag 155 (decimal) with the value "-i" (on the standard DHCP server, this is done by the following command: option option-155 "-i";). It is interpreted by bpbatch as the command line, and -i stands for "interactive".

Boot the client computer. You might shortly see

Congratulations ! You have started the batch interpreter... If you are curious about what you can do with it, continue reading the next section. If you are on a hurry, skip it and go directly install the operating system of your choice. If you have any doubt about a command within the interpreter, type help.

Note that you can run the same interpreter within DOS and Linux by running the MrBatch program. There are a only very few differences (the Linux version do not have graphics support and the DOS version can only send BOOTP and TFTP requests if the BootProm is not hidden by the operating system).

It may be a good idea to read now the section about the Syntax Rules of BpBatch, and in particular the paragraphs on File References and on The Cache Filesystem. This will help you understand the examples.

Once all operating systems will be set up, you will have to make a menu to let the user choose the one he wants. You should be able to discover by yourself how to make such a menu. All necessary commands are documented at the end of this document.

Discovering BpBatch

Try to type LogVars. You should get about thirty variables listed. Roughly, the first are BpBatch settings, then come all parameters extracted from the BOOTP/DHCP reply, and the last variable is a list of disks sizes, in Megabytes.

Type GetPartitions part, then LogVars again. There should be one more variable containing the list of defined partitions on your first hard-drive. Assuming that the first partition is either BIGDOS, FAT32 or LINUX-EXT2, try LogDir "{:1}" to get the content of the root directory, then LogDir "{:1}/usr" if there is an usr directory. You can even try LogTree "{:1}/etc" to get a directory tree.

Put a GIF file (format GIF-87a, interlaced or not, but NOT GIF-89a) on your TFTP server. We will suppose that the file is named image.gif. You can copy it wherever you want with the following command: Copy "image.gif" "{:1}/temp/image.gif". Or you can use it directly from the server. Now type Logvars "V*" and look at the value of the VESA variable. If it is On, which is most probable, that means you have a VESA-compliant video adapter. You can list the available video modes using Echo "$VESA-Modes". To display your image try the following command: DrawGif "image.gif". The image should be on the upper left corner of the screen. You can draw it on another place by specifying X and Y coordinates after the image name. You can also draw text with DrawText 200 200 "Hello world" yellow. Or draw an empty window with DrawWindow 200 200 300 150. To insert a title when you create a new window, try DrawWindow 200 200 300 150 "My Window". When you are tired of graphic mode, simply type CloseGraph.

Note on graphics : by default, all graphical routines work in the 800x600 VESA mode (with 256 colors), which is the first field of the VESA-Modes variable. If you want to use a different video mode, change the variable in order to have the requested video mode as the first field of the list.

Now take a text editor, and create a file named test.bpb in the tftpboot directory with the following content:

DrawWindow 150 200 400 160 "Identity check"
TextAttr Black LightGray
At 15,20 Print "Username : "
Input username 8
At 17,20 Print "Password : "
Getpasswd userpass 8
if "$username" != "smith" goto again
if not "$userpass" match-passwd "BpR8oiIlRR9bo" goto again
DrawWindow 200 200 150 100 green blue "Congratulations"
DrawText 220 250 "You got it !" yellow
WaitForKey 3

In your BOOTP/DHCP configuration, change the option-155 from "-i" to "test", and reboot the client computer. The small script should run automatically, and ask you for a username and password. If you do not type smith and justdoit, you wont be able to boot the computer. Later you will learn how to use a Unix, NT or Radius server to check valid user names.

4.4 Setting Up Linux

In order to set up Linux, you will need to boot the floppy disk provided with the RedHat Linux distribution. BpBatch includes a command that can redirect the boot to the floppy: FloppyBoot.

Set up RedHat Linux on your client, with network support, and any packages you may want. You may want to recompile the kernel to better fit your hardware, but it is not necessary.

Configuring the Client

It is probably a good idea to include BOOTP support to the kernel, so that you do not have to customize the client IP address manually.

In order to reduce network load, you might also want to setup the filecache for caching on the hard disk files that are loaded by NFS. Roughly, the principle of the filecache is that whenever a symbolic link from the cache subdirectory is followed, it is replaced by its target. If the target is itself a subdirectory, each entry of the subdirectory becomes a symbolic link to the original entry of the foreign filesystem. The filecache has been written by Unifix GmbH, and is part of Unifix Linux 2.0. It is freely distributable, and you can get the necessary files from In order to use the filecache, you have to

If you successfully followed each of these steps, you should have the filecache working next time you boot, as long as you do not forget to use your patched kernel.

Testing the Configuration

Copy your compressed kernel image (zImage, bzImage, vmlinuz or whatever you call it) to the server /tftpboot directory as linux.krn. If you had to unplug the bootprom from the PC, you can now plug it again. When BpBatch starts, type LinuxBoot "linux.krn" "root=/dev/hda1 BOOT_IMAGE=linux" (assuming that the root ext2 filesystem is on the first partition). Alternatively, if you did setup your configuration on a computer without bootprom, just boot let it boot using the loader you installed (lilo, ...). But in the later case, if you want the filecache to work, you should have explicitely installed your kernel with filecache support at the right place.

Wait until the system comes up. If you installed the filecache, you can check that /usr has exploded into a directory with some symlinks and some already-exploded directories. Now start the programs that the end-users will use most of the time, in order to load them once for all to the hard disk.

You can still make adjustements to your configuration, like on any stand-alone linux station.

Building the Disk Image

When you are happy with your configuration, login as root, go to the /tmp directory and run our mrzip program. MrZip is a command interpreter like BpBatch, but it can understand more commands than BpBatch does. In particular, it can understand the following commands:

filter -"tmp/*"
filter -"var/log/*"
fullzip "/" "/tmp/linux.imz"

This will create a disk image in /tmp/linux.imz. Move it to the server /tftpboot directory. Then copy the following batch file to /tftpboot/linux.bpb:

setpartitions "linux-ext2:992 linux-swap:32"
fullunzip "linux.imz" 1
clean 2
linuxboot "linux.krn" "root=/dev/hda1 BOOT_IMAGE=linux"

The BOOT_IMAGE argument is to stay compatible with lilo for RedHat 5.1 and later rc.sysinit.

Your remote-boot linux configuration is ready ! You can now either set the BOOTP-option-155 to "linux", or type include "linux.bpb" from within BpBatch to test it.

System Maintenance and Upgrades

If you want later to upgrade software, install bug fixes and security fixes, proceed as follow:

That means, you can upgrade software on your server-based configuration as if it were a purely local install.

4.5 Setting up DOS 6 and Windows 3.1

On the client computer, boot on your favorite dos floppy disk (either remove the bootprom or type FloppyBoot within BpBatch). Format the dos partition of your hard-drive with the /S option, in order to put the operating system on it. The size of the partition is not important, as disk archives created with MrZip Create a DOS subdirectory, copy DOS in it. Install your favorite network client (for instance Microsoft LanManager), Windows 3.1, and so on. If you use Microsoft LanManager, do not use DHCP for the IP configuration as it is a very poor implementation that will almost surely fail with reasonable network load. To do that, add the following lines in your protocol.ref file, in the section that loads tcptsr (of course, replaces the xxx by your true IP parameters):

        IPADDRESS0 = xxx xxx xxx xxx
        SUBNETMASK0 = 255 255 xxx xxx
        DEFAULTGATEWAY0 = xxx xxx xxx xxx
        DISABLEDHCP = 1

Do not be afraid to use EMM386 to optimize the memory usage, and even to include the area where you put your network adapter ROM, since it is not used anymore at this time. But carefully exclude the network adapter RAM, or you will not be able to connect to your server. Use the NOEMS parameter.

If you want to ensure that the client machine cannot be used without a valid login name, download our nobreak pseudo-device driver (available at and run it at the beginning of your config.sys. Then add something like this to your autoexec.bat:

rem -- we use the dummy file c:\logged as a flag
del c:\logged >nul
echo Please type in your login name and password
net logon *
rem -- the login script should have created c:\logged
if not exist c:\logged goto loginneeded
del c:\logged
rem -- now enable break again
echo Yes >NOBRK

Ensure that your client boot well by rebooting the client and evaluating the following commands within BpBatch interactive mode:


Building the Disk Image

On the server, make a share called admin for instance, on which you will put some stuff for the system administrator. If the server is a Unix machine, it is a good opportunity to put in admin a softlink to the /tftpboot subdirectory, so that you can put images in it directly from the client. Within admin, create a /utils subdirectory and put the following files in it:

You might also like to put in the same directory a simple MrZip script named zipdos.mrz file that contains the commands needed for building a DOS image, like this one:

filter -"lanman.dos/lmuser.ini"
filter -"temp/*"
filter -"*.swp"
fullzip "c:/" "L:/tftpboot/dos.imz"

Now go back to your client, mount the admin volume on drive L:, go to your utils directory and type the following command:

        mrzip -b zipdos

One minute later, you will have a new file in the server /tftpboot subdirectory called dos.imz, which is a compressed image of your hard disk. Copy the following batch file to /tftpboot/dos.bpb:

setpartitions "bigdos:1024"
setbootpart 1
fullunzip "dos.imz" 1
hdboot :1

Your remote-boot DOS configuration is ready ! You can now either set the BOOTP-option-155 to "dos", or type include "dos.bpb" from within BpBatch to test it.

Adapting the configuration for other machines

If you want to customize some settings according to the machine, typically the IP settings since Micro$oft DHCP is buggy, you can setup BpBatch to change some files before booting. Firsti go to the lanman.dos directory and do

        copy *.ini *.ref
Then edit the .ref files and replace all fixed parameters with BOOTP variable names as in the following examples:
        computername = ${BOOTP-Host-Name}
        ipaddress0 = ${MS-IPAddress}
        subnetmask0 = ${MS-IPSubnet}
        defaultgateway = ${MS-IPRouter}
Then rebuild the disk image as previously. Note that for IP parameters, we do not use the BOOTP variables directly because LanManager needs then as space-separated numbers instead of dot-separated numbers. Change dos.bpb to the following:

setpartitions "bigdos:1024"
setbootpart 1
fullunzip "dos.imz" 1
set MS-IPAddress="$BOOTP-Your-IP"/.= /
set MS-IPSubnet="$BOOTP-Subnet-Mask"/.= /
set MS-IPRouter="$BOOTP-Routers"/.= /
patch "{:1}lanman.dos/protocol.ref" "{:1}lanman.dos/protocol.ini"
patch "{:1}lanman.dos/tcpputils.ref" "{:1}lanman.dos/tcputils.ini"
patch "{:1}lanman.dos/lanman.ref" "{:1}lanman.dos/lanman.ini"
hdboot :1

If you prefer, you can also put the .ref files in the server /tftpboot directory instead of in the disk image.

We like to be able to easily change the computers configuration without rebuilding the image. To do that, copy your autoexec.bat and config.sys as autoexec.ref and config.ref to the server /tftpboot and add the following two lines to the batch file above:

        patch "autoexec.ref" "{:1}autoexec.bat"
        patch "config.ref" "{:1}config.sys"
You can then freely change the files and even customize them with machine-dependant values obtained from BOOTP.

After making any change to the client machine configuration, do not forget to rebuild the disk image using mrzip if you want to preserve your changes.

System Maintenance and Upgrades

If you want later to add new software or change anything else, proceed as follow:

That means, you can upgrade software on your server-based configuration as if it were a purely local install.

4.6 Setting up Windows 95

In previous versions of this document, we used the Microsoft server-based installation of Windows 95, but it was really too much pain and not much worth:

Consequently, we throwed away of this document all the informations and bug-workaround collected during months (you can still find them as a HTML document at and turned to our new disk-based remote-boot concept. Basically, the configuration for Windows 95 is now almost as easy the configuration for DOS.

Setting up a Stand-Alone Client

Setup a regular Windows 95 client, either starting from scratch as explained in the configuration of a DOS client, starting from the DOS client and installing over the network (that is what we did). You can also start with a preconfigured Windows machine, but you will probably have less knowledge of what stuff is on the hard disk.

Proceed as described above for a DOS client. It is usually NOT necessary to use EMM386 with Windows 95. If you are using Windows 95 OSR2 (alias MSWIN 4.1, alias Windows 95 service pack 1, alias Windows 95 with Internet Explorer), you should add the following line in the [Options] section of MSDOS.SYS (yes, it is a text file):


This will let Windows know that you do not want ScanDisk to be runned automatically at boot time.

If you want to reduce network and server load (which will improve your system performances) while keeping all softwares on the server, you should consider installing the excellent Shared LAN Cache, from Measurement Techniques, Inc (see This software runs on each client computer, and caches to the local hard disk every data obtained from the network. Even MS-Office starts much faster the second time you run it... You need one license per client computer, but it is not very expensive, and the firm make special prices for universities and colleges. The best thing to do is to go to their Web site and download the free evaluation copy.

Building the Disk Image

Your MrZip script will be named zipwin95.mrz and contain:

filter -"temp/*"
filter -"*.swp"
fullzip "c:/" "L:/tftpboot/win95.imz"

To build the image, mount the admin volume on drive L:, go to your utils directory and type the following command:

        mrzip -b zipwin95

A few minutes later, you will have a new file if the server /tftpboot subdirectory called win95.imz, which is a compressed image of your hard disk. If your compressed image was bigger than 87 MB, it has probably been splitted in two or more fragments. These fragments will automatically loaded one after the other when needed. Note that an image bigger than 87 MB will usually take More than one minute to uncompress and may irritate your users. Our Windows 95 image is only 70 MB big, because most software (except Office and Explorer) completely reside on the server. Only 45 seconds are needed to uncompress the image and restore the full disk.

Copy the following batch file to /tftpboot/win95.bpb:

setpartitions "bigdos:1024"
setbootpart 1
fullunzip "win95.imz" 1
hdboot :1

Your remote-boot Windows 95 configuration is ready ! You can now either set the BOOTP-option-155 to "win95", or type include "win95.bpb" from within BpBatch to test it.

Adapting the configuration for other Machines

The big difference between Windows 3.1 and Windows 95 is that the later includes code for Plug-and-play , ie. automatic detection of your hardware. This not a bad thing in itself, but the trouble is that it is often too sensible, and that it sometimes fails.

If you try to start another client with exactly the same boot image, you will probably get several messages during startup telling that Windows has detected new hardware: a new sound card, a new hard-disk, a new network card, and even a new mouse... There can be two reasons for that:

The fact that Windows 95 discover that the hardware has changed may not be a problem if the plug-and-play works as-is, but it become a problem when the plug-and-play does not work. For instance, Windows 95 plug-and-play for our Logitech PS2/aux mouse does not work, and result in no mouse at all. To solve such kind of problems, arrange to have all computers as similar as possible, or make different images for different hardware. Later, you will discover that you can simply use the same image and just have several copies of the registery, that you can copy after having restoring the disk image but before booting.

The thing you cannot avoid to differ between computers is the network card. PCI cards usually do not mind, but ISA Plug and Play do. Bad luck for us, the plug-and-play code for our SMC EtherEZ card hangs the computer. The only solution is to let Windows 95 believe that it already know the network card, and that it is not necessary to trigger plug-and-play. The trick for doing that is to automatically insert an entry for the network card in Windows 95 registery, before starting it. Note that this trick is not any more needed with most PCI cards.

Move the autoexec.bat to the server as described above for DOS. Edit it (on the server) and add the following lines:

rem --- Patch Windows registery in order to avoid plug-and-play detection
regedit /L:c:\windows\system.dat /R:c:\windows\user.dat c:\temp\patch.reg
regedit is a standard Windows 95 program that let you browse the registery if you start it from within Windows 95, or do simple operations on the registery if you call it from DOS. Run regedit under Windows 95, search for your network card, usually under
and export the branch using the File menu. This will create a text file, that you should same as patch.ref in the server /tftpboot diretory. Edit this file and find out where the card ethernet address is stored (do that on two different machines and compare the files if you can't find it by yourself). Replace it by a pettern in the form ${MACID}. Then add lines to the win95.bpb script like this:
        set macid = "$BOOTP-Client-ID"
        patch "patch.ref" "{:1}temp/patch.reg"
(do any necessary string manipulation for setting MACID if it is not exactly the client Ethernet address). That's all, your clients should not any more try to autodect the network card.

Once again, this whole trick is not necessary when using PCI network adapters. Incidentally, we can use the same mechanism for automatically configuring the hostname, which Windows 95 does not seem to take into account when configuring through DHCP. We just add the following line to our patch.ref file:




Using this small registery trick, your configuration should normally be portable for all machines with similar configurations. If you cannot avoid that Windows detect some hardware as new on one machine, try to rebuild the disk image from this machine. This will include the registery configuration specific to this machine into the image, and hopefully supress the problem.

System Maintenance and Upgrades

If you want later to upgrade software, install bug fixes and security fixes, proceed as follow:

That means, you can upgrade software on your server-based configuration as if it were a purely local install.

4.7 Setting up Windows NT

We do not use Windows NT for remote-boot client computers but we have tested our system to ensure that it work as well. And it works.

As our utilities currently have no support for NTFS (we neither have the documentation nor the time to do that, but I would be happy to help anyone who is interested in doing it), you will have to install NT on FAT16 (simply do not convert your partitions to NTFS during the setup).

Copy your win95.bpb boot script to winnt.bpb. Change the setpartitions line in winnt.bpb to the following:

        setpartitions "BIGDOS:512 BIGDOS:512"
Then boot Windows 95 using this script, and install your NT client on drive C. Do not worry about the second partition for now. Do not install too much stuff, or you will get a really large and slow-to-uncompress image. Remove Windows 95 from the disk disk C, you do not need it in a Windows NT image (the boot menu is handled by the bootprom, not by NT boot loader).

Reboot your computer in without overwriting the hard disk, ie. do not execute the winnt script but just

Your NT station should start-up correctly. Make any necessary customization.

Building the Disk Image

The trouble with Windows NT is that direct disk access is prohibed by the kernel. That means, MrZip will not even be able to read the boot sectors. The best way to do an image is then to boot Windows 95 and to run MrZip from a DOS window. To do that, change the winnt.bpb script so that the Windows 95 image is not restored on the first but on the second partition:

setpartitions "BIGDOS:512 BIGDOS:512"
setbootpart 2
fullunzip "win95.imz" 2
hdboot :2

(if you have any supplementary patch, change the "{:1}" to "{:2}"). Boot with this script; you should have Windows 95 running, but a new drive D: should be available, with Windows NT inside.

Make your disk image as usual (but on D:, of course), and save it as winnt.imz on the server /tftpboot directory. Edit one last time the winnt.bpb script like this:

setpartitions "BIGDOS:512 BIGDOS:512"
setbootpart 1
fullunzip "winnt.imz" 1
clean 2
#fullunzip "win95.imz" 2
hdboot :1

Your Windows NT remote-boot configuration is ready. Of course, if you do not like to have two partitions, you can setup a single partition instead. But when you have to rebuild the image, you will have to setup the second partition again for booting Windows 95.

System Maintenance and Upgrades

If you want later to upgrade software, install bug fixes and security fixes, proceed as follow:

That's all, folks !

4.8 Troubleshooting (FAQ)

This section lists most frequently encountered problems.

The image download never ends

You are probably using a standard TFTP server, and it cannot handle more than 65535 packets of 512 bytes (or even 32767 packets for the Solaris server). That is, your image must be fragmented in pieces of no more than 30 MB (or 15 MB for Solaris). See under CopyArchive for instructions on fragmenting an existing image. But you should seriously thing about using InCom's extended TFTP server, as it is much more efficient (it uses packets of 1408 bytes instead of 512 bytes).

The archive decompression fails immediately

There are three possibilities. Either the image is really corrupted on the server (try use MrZip to see if it is the case), or the file transfer has failed because of TFTP timeout, or because of incompatible protocol.

TFTP timeout occurs when the network is too heavily loaded (for instance if you try to download a huge image with more than four clients at a time). In this case, BpBatch does not retry indefinitely because it would not help. Shut down a few computers and retry with no more than four computers (or maybe even three). If you often need to download images for a lot of computers, you can try our special Broadcast TFTP server (see the section dedicated to it).

Incompatible protocol is caused by using a standard TFTP server (typically the one built-in in your UNIX server) while asking BpBatch to work with enhanced TFTP. If you use a standard TFTP server, you should remove the .P extension (see the explanation in the next question).

The computer hangs instead of downloading/unzipping (1)

If you are using Incom's TFTP server, try to add -s 1408 59 to the command line. If you are not using an enhanced TFTP server, remove the .P extension from BpBatch filename on the server and in bootptab.

Detailed explanation : this problem occurs if you did not setup an extended TFTP server but you used bpbatch.P as the bootfilename DHCP/BOOTP tag. BpBatch will indeed try to connect to an extended TFTP server when the bootfilename ends with a .P extension. To solve this problem, you can either remove the .P extension at the end of the bootfilename (it will tell BpBatch to use standard TFTP) or install an extended TFTP server. The only supported extended TFTP server today is the one provided by Incom. You can find compiled binaries on their web site, or on our distribution directory. For Incom's TFTP server to properly work with the extended TFTP feature, you must add -s 1408 59 to the command line.

The computer hangs instead of downloading/unzipping (2)

May be your computer has a bad VESA support. Try giving the -v command-line argument or setting the VESA variable to "OFF".

VESA scrolling is broken

We use a VESA 1.1 function for scrolling. If your video adapter does not support VESA 1.1, forget it. If the scrolling works for one page, but then produces a strange strippled pattern, do not worry. This is a known bug, I will fix it as soon as I have time for it (VESA scrolling is not really essential...)

There is a corrupted file in the cache

When a file in the cache is corrupted by an external program, it is automatically removed from the cache. When a file in the cache is not fully written (because the computer is turned off during the file transfer), it is also automatically removed. But if the server transmits a corrupted file or if the transfer aborts from the server side, it is possible that this file stays in the cache. You can clean-up the cache simply by holding both shift down while BpBatch access it for the first time. Alternatively, you can evaluate clean -1 in interactive mode.

The EXIT command does not work in a batch file

This is not a bug. Exit is not a command. There is no exit or quit command because it does not make any sense to exit from a boot script without booting. And MrBatch is really the same program as BpBatch. What you can do instead is calling HdBoot. This makes sense, and the DOS version will cleanly exit instead of rebooting. Note that you can exit from the DOS version at any time by pressing Ctrl-Break. This will restore all hooked interrupts before leaving.

The Print command does not print

If you try to print something and immediately enter interactive mode, you may not see your text. This is because your text was written on the runtime screen and the Interact command has switched the display to the Log screen. Just put a GetKey after the print commands and you will see the text output.

MrZip says Malloc failed

MrZip needs a lot of conventional memory to run. If you encounter this problem, first ensure that you have unloaded the bootprom either using HideBootprom or using InCom's bputil. If you run MrZip from bare MS-DOS (not within Windows 95 DOS box), you should use EMM386 to load the network drivers high in order to get as much conventional memory as possible. From a Windows 95 DOS box, there is usually no problem (as long as you have not left your old 16-bit stuff in your autoexec.bat when you installed Windows 95).

MrZip aborts while reading directories

This bug has already been fixed once. Get the latest release of MrZip. If the problem persists, try to build your image with Trace set to "ON" (and usually PauseLog set to "OFF"); this will let you discover which file causes the problem. Send a detailled bug report.

MrZip cannot access some file

MrZip is probably trying to read a locked, open or special file, such as Windows swap file. Such files should usually not be included in the image and should be filtered out (using the filter command). It is also possible that the operating system is playing you a trick. If MrZip does not tell you what file causes the problem, try to build your image with Trace set to "ON" (and usually PauseLog set to "OFF"). You can also try to use direct disk access (that is, do not refer the source partition as "C:" or "/" but as "{:1}" or whatever partition it is). Using direct disk access is usually slower because we have less buffers than the operating system, but it may be sometimes more reliable.

Disk images are always reloaded from the server

Disk images are stored in the special cache area and should not be reloaded if they have not changed on the server. However, as the cache area always starts after the last used partition, changing the total size of partitions will move the location of the cache and thus destroy its content. Another possible reason for a file disappearing from the cache is that the previous file has grown more than one-and-an-half times its initial size. The file would then have been overwritten and need to be downloaded once again. This should almost never occurs. A third possible reason is a too small cache area. If the free space left outside the partitions is less than one-and-an-half times the sum of all compressed image sizes, only the most recently used images will be present in the cache and the other will have to be reloaded on demand.

Red Hat Linux 5.1 does not boot properly

This distribution assumes Linux was booted using lilo and checks for the BOOT_IMAGE command line argument (in /etc/rc.d/rc.sysinit). Simply add it in the linuxboot call, or change your rc.sysinit.

The broadcast TFTP ramdisk hangs (Got in bound state)

Linux dhcp client is a program that dynamically changes the IP address of the client according to DHCP offers. If the address is offered forever (infinite lease time), the DHCP client just set the address and returns (this is what we expect). However, if the lease time is limited, the DHCP client must remain loaded and ask for new addresses every few minutes. And if the DHCP client does not return, MrBatch will never be loaded... The solution is to give an infinite lease time (sometimes encoded as -1).

File access hangs under BpBatch, but not under MrBatch

This problem occured on an AMI BIOS dated 94/07/25. We investigated a little bit, and found no solution. It seems that this problem is due to a bug in this BIOS (some register or memory location must be destroyed).

Unzip of a fragmented archive fails (Malloc failed)

This problem was introduced with PXE compatibility, but has now been fixed. Please get the latest version.

MrBatch and MrZip complain about the terminal under RedHat 5.x

This problem has been fixed in the 9th of August version of MrBatch/MrZip. There was a problem with a new version of ncurses which has been released with RedHat 5.1.

" cannot open shared object file" under Linux

MrZip has been linked to the version 3.0 of libncurses. You can use other versions of libncurses only if they are newer than version 3.0. To use a newer libncurses, all you have to do is to create a soft link from to your file. With RedHat 5.1, you can use the following command : cd /usr/lib ; ln -s libncurses.4.2 libncurses.3.0 You can also download a version recent version of mrzip/mrbatch. Starting from the 10/25/98, mrbatch is now compiled under RedHat 5.1.

MrBatch and MrZip do not start under Linux (file not found)

This problem is the reverse of the previous one. Now that the distribution is libc6 ready, it cannot be used any more with libc5. If you encounter this problem, simply upgrade your Linux box (Well, if we hear too much complaints, we might try to keep two distributions...).

I can not access other mode than the default 800x600 VESA mode

You should first display the contents of the VESA-Modes variable, to see if your hardware support the mode you would like to use. Then, try one of the two ways to select a special VESA mode :

BpBatch prints a "Malloc failed" message when restoring multiple fragments images

We corrected a bug in the memory allocation functions of BpBatch. You should make sure that you have a version of BpBatch which has been released after september the 22nd 1998.

Fullunzip using the Linux version of MrBatch always fails

We corrected this problem in the 09/22/1998 release.

Scandisk says my disk is corrupted

The 10/25/98 release did correct a problem with large images. Try to download a recent version of BpBatch.

My RedHat boot floppydisk does not work with FloppyBoot

This bug has been corrected in the 10/25/98 release.

My FAT32 disk image does not boot properly

This bug has been corrected in the 02/09/99 release.

5. Remote-Boot Tools Reference Manual

This section provides detailled informations on the use of the tools we developped at the CUI, University of Geneva for this remote-boot configuration.

5.1 BpBatch, MrBatch and MrZip

These three names stand for three variants of the same program, with the following characteristics:

Command Line Arguments

All programs accept the same syntax of arguments. MrBatch and MrZip take them from the command line, while BpBatch look for them in the BOOTP option 155 (decimal). Here is the syntax of the arguments:

        [-x] [-l] [-b] [-v] [-w] [-i] [script-basename]
where: The script-basename is optional. If provided, MrBatch and BpBatch load the file with the .bpb extension, and MrZip loads the file with the .mrz extension. If not provided, MrBatch and MrZip run in interactive mode while BpBatch loads the file with the same basename as the BOOTP Boot file and a .bpb extension.

Syntax rules

The following rules apply when BpBatch parses an input line.

Empty lines are ignored. Lines starting with a sharp (#) are treated as comments and are not interpreted. Lines starting with a column (:) are treated as labels and are not interpreted.

String expressions

Strings are delimited by opening and closing double-quotes:

        "Hello world"
To include double-quotes within a string, quote them using a backslash:
        "I said: \"Hello world\""
Strings can be postfixed with a few operators. Operators can be chained by postfixing one after the other. For informations about the string length and word count operators, see under "Numerical expressions".

Numerical expressions

Numerical expressions work on 32-bits integer numbers (from -2,147,483,646 to 2,147,483,647). Hexadecimal octal and binary numbers are not understood. Whenever a numerical expression is expected, the following are recognized:


A few commands expect durations as arguments. Durations are measured in seconds, with a precision of up to a tenth of second:

        Delay 3                 waits for 3 seconds
        Delay 0.3               waits for 3/10 seconds


Whenever a color is expected, you can either use the numeric value of the color or its symbolic name (case-insensitive). The following colors are recognized

        Black           0
        Blue            1
        Green           2
        Cyan            3
        Red             4
        Magenta         5
        Brown           6
        LightGray       7
        DarkGray        8
        LightBlue       9
        LightGreen     10
        LightCyan      11
        LightRed       12
        LightMagenta   13
        Yellow         14
        White          15

File References

File names are strings. They must therefore always be enclosed between double-quotes. File names are case-sensitive on case-sensitive filesystems, case-insensitive on case-insensitive filesystems. Slash and backslash can be freely used one in place of the other. Do not forget to double backslash since a single backslash is an escape character.

There are two kinds of file references:

Direct disk files are referenced using the following notation:

The disk number can be omitted and defaults to zero. For instance, "{:1}/usr/bin" points to /usr/bin assuming there is such a directory on the first partition. Direct file I/O is solely based on our own file access routines (we do not use the operating system).

There are two special partitions. Partition zero corresponds to the hard disk master boot record (MBR) and has a pseudo file-system which let you access the boot code. Partition minus-one (-1) corresponds to the cache filesystem (see below).

Under BpBatch/MrBatch, foreign files correspond to remote files on the TFTP server when the BootProm is available:

        "help.bpb"           is the file help.bpb in the /tftpboot directory
        "gifs/MyImage.gif"   is a file in /tftpboot/gifs
Other TFTP servers can be referenced :
If the other server is behind a gateway :
One can also specify a specific port for the TFTP connection :
There can be only one open remote file at a time. If the BootProm is not available, remote files are emulated using the operating system file I/O, but the same restriction apply.

Under MrZip, foreign files correspond to files as seen by the operating system. There is no limitation, and foreign files can be used wherever direct disk files can be. Foreign files are usually faster than direct disk files, because the operating system has more buffers. Foreign files can refer to network files if supported by the operating system.


The Cache Filesystem

In order to reduce network load and to fasten the boot process, disk archives, linux kernels and possibly other files are cached on the hard disk. This disk cache is located at the end of the hard disk, between the last cylinder allocated in the partition table and the last physical cylinder of the disk (out of any allocated partition). There MUST be room between the last partition and the end of the disk if you want the cache filesystem to work. The cache filesystem MUST work if you want to restore a disk image.

The disk cache is organised in a volatile, CRC-validated filesystem : Each directory entry and each 32 KB data block is validated by a 32-bits CRC. Whenever a directory entry or a data block unexpectedly changes, the file is automatically removed from the cache and downloaded again upon the next request.

You can freely access the cache filesystem from within BpBatch, MrBatch and MrZip using direct disk access on the special partition "{:-1}". To see the content of the cache, just type :

        logdir "{:-1}"
If the cache ever gets corrupted and is not automatically cleaned (which should never occurs), you can either type :
        clean -1
(in interactive mode) or hold both shifts down when BpBatch access the cache for the first time.

Special variables

Some variable are initially set and/or have special meanings. Some of them exist within all programs, other are only available under MrZip and other are only available when a BOOTP/DHCP reply has been received.

General variables

See also BOOTP variables and MrZip-specific variables.

MrZip-specific variables

The following variables are only used within MrZip.

BOOTP variables

The following BOOTP-... and DHCP-... variables are recognized, as long as a BOOTP/DHCP reply has been received (TCP/IP Bootprom must be reported as detected):


Other BOOTP/DHCP parameters can be used under the name

where n is the decimal representation of the BOOTP option number.

Do not mix-up BOOTP-Gateway-IP, which is the gateway to use for TFTP and should be if the TFTP server is in the same subnet, and BOOTP-Routers, which contains the default IP gateway(s). The TCP/IP Bootprom sometimes seems to set the value of BOOTP-Gateway-IP from the value in BOOTP-Routers, causing each TFTP ack packet to be sent to the router first. To avoid such behaviour, if your TFTP server is in the same subnet as the client, force BOOTP-Gateway-IP to (thanks to Maciek Uhlig for having pointed out this problem).

Monitoring commands

This section lists commands for monitoring the system state. Optional arguments are listed between parenthesis (I would have prefered square brackets, but LaTeX do not like them at this place...)


Show the log and turn to interactive mode until QUIT or EXIT is entered. Type HideLog before quitting if you want to avoid disturbing log messages during batch execution.

Help (topic)

Load the on-line help file (bpbatch.hlp) and display the description of the given topic. If no topic is provided, or if the topic is unknown, display the help index.

Log "text"

Display the string on the log. No return/linefeed is implicitely added.

Echo "text"

Display the string on the log and go to the next line. Equivalent to

        Log "text\r\n".

LogVars ("pattern")

Log (ie. display on the log) all variables matching the given pattern. The pattern can contain wildcards (? and *).

Example: LogVars "BOOTP-*"              list all BootP variables
LogDir "path/pattern"

Log (ie. display on the log) all files from the given path that match the pattern. The pattern can contain wildcards (? and *).

Example: LogDir "/usr/g*p"              list files names like g...p
LogTree "path"

Log the directory tree starting with the given path as root.

LogFile "filename"

Log the content of the file. The file must be no more than 64 KB big.


Make the log visible if it was hidden. Automatically performed when ESC is pressed with "$AutoShowLog" == "ON" and when entering interactive mode.


Prevent log messages to appear on the screen. Default state when BpBatch, MrBatch and MrZip are started on a script file.


Record all log output to a 64 KB buffer until EndCapture is issued. Wrap around buffer if the log output is more than 64 KB big. This command can be used to create a text file with an arbitrary content. The EndCapture MUST occurs within the same batch file.

EndCapture ("filename")

End up the capture of the log. If a filename is given, store the captured text to a file. Otherwise, discard it.


Make a sound. This command is equivalent to Echo "\007".

Control commands

This section lists commands that control the batch execution. Optional arguments are listed between parenthesis.

Include "filename"

Load the given file and start up the parser on it. Go back to the current point when the include file processing is done. The interpretation of characters above ASCII 127 within the include file depends on the value of $IsoLatin at the time the file is included.

OnExit command

Setup an exit-handler that will automatically be evaluated at the end of current batch file.

Goto label

Move the execution cursor to the given label (ie. the line starting with :label)

Eval "command"

Perform all substitutions on the "command" and run the parser on it.

If ...

  If (not) <expr1> (==|!=|<|>|>=|<=|=>|=<|<>) <expr2> <command>
  If (not) (ci) "str1" (==|!=|<|>|>=|<=|=>|=<|<>) "str2" <command>
  If (not) (ci) "str1" Match-Expr "pattern" <command>
  If (not) (ci) "str1" Match-Passwd "unix-passwd" <command>
  If (not) (ci) "str1" in "wordlist" <command>
  If (not) (ci) "str1" in-file "filename" <command>
  If (not) exist "filename" <command>
  If (not) valid <disk>:<partition> <command>

These commands execute command; if the test succeeds. The 1st form compares two numerical expressions. The 2nd form compares two strings, optionally case-insensitive. The 3rd form tests if "str1" matches the given pattern (wildcards allowed). The 4th form tests if the clear password "str1" matches the Unix-crypted password. The 5th form tests if "str1" is included in the word list. The 6th form tests if "str1" is included in the word file. The 7th form tests if the given file exists. The 8th form tests if the given partition is valid (i.e. formatted). This form is only supported by BpBatch versions after February 1999.

Set ...

  Set variable = "string-value"
  Set variable = <expr>

Setup a value for the given variable. If the given value is a numerical expresison, it will be implicitely converted to a string. A variable can be used anywhere by refering it as $variable or ${variable}. If the resulting reference is to be interpreted as a string, it should be enclosed between double quotes: "$variable" or "${variable}".

Delay duration

Waits until the specified duration (expressed in seconds) expired. See also the paragraph on the format of durations.

GetTime variable, GetDate variable

Get the CMOS time and store it into variablein the form HH:MM:SS. Get the CMOS date and store it into variablein the form YY/MM/DD. This can be used to customize the behavior of your boot scripts depending on the time of day or on the date.

SetTime "HH:MM:SS", SetDate "YY/MM/DD"

Set the computer CMOS time or date to the given value. If you have a security gateway (our special TFTP server) running, you can automatically adjust the CMOS time and date of the client computers at each boot by evaluating the following command:

        include "$Security-Gateway:gettime"
If you want to understand what this command does, just type:
        logfile "$Security-Gateway:gettime"


Turn off the computer. This command only works if the computer is Advanced Power Management (APM) compatible.

Keyboard-related commands

This section lists commands that let you monitor the keyboard input. Optional arguments are listed between parenthesis. See also under National Language Support.

GetKey (variable)

Indefinitely wait until a key is pressed and store it in the variable.

WaitForKey duration (command)

Wait until a key is pressed for no more than duration seconds. If no key has been pressed after the given time, evaluate the command. Otherwise, leave the key in the keyboard buffer. See also the paragraph on the format of durations.

Input (variable (max-length))

Read a return-terminated string from the keyboard and store the result string in variable (without the terminating return). If max-length is given, do not allow the user to enter more than this number of characters.

See also GetPasswd under Security-related commands.

OnKey "c" command

Setup a key handler that will automatically evaluate the given command when the key "c" is pressed (except is explicitely waited by a GetChar or an Input command). If the string "default" is used instead of a single character, the command is executed if any other key is pressed.

Text output commands

This section lists commands used to perform regular text output. All these commands can be used in graphic mode also, with the same behaviour (except that text mode provides 80x25 characters while graphic mode provides 100x37, because graphic mode characters are of size 8x16). Optional arguments are listed between parenthesis. See also under National Language Support.

Print "text"/expr

Print the specified string/expression at current cursor position and using current text attributes, then move the cursor. Add "\r\n" to the end of the string to go to the next line.

TextAttr fg-color bg-color

Setup the text attributes. One can also put a single numeric value representing both colors and defined as 16*bg-color+fg-color.

If you need more fantasy, you can use LoadFont. See under National Language Support.

At line,col (command)

Move the cursor position to the specified position and evaluate the command if provided.

Example: At 10,20 Print "Gnats and rats !"
Clear (color (pattern-char (top,left,bottom,right)))

Fill the given text area with the given pattern-char (either a string or the decimal ascii code). The area defaults to the full screen, the pattern char defaults to the full block (ASCII dec 219) and the color defaults to black (clear screen). Move the cursor to the upper left corner of the cleared area.

BpMenu backward compatibility commands

  .ATT (<attribute>)
  .CLS (<attribute>)
  .DEF <key> (<timeout_val>)
  .KEY <key> <filename>
  .POS ((<x>) <y>)
  .PWD <key> <cpasswd>
  .WLN (<text>)
  .WRT <text>

See InCom's manual for more infos. We wrote some time ago a program program for editing menu files using this syntax, but it is preferable to make your menus using the new explicit syntax. Note that the .PWD command is not implemented because we do not now the password crypting algorithm used by InCom GmbH.

Graphics output commands

This section lists commands used to perform graphic-mode output. For the functions listed in this section, coordinates are given in pixels. You can also use all text output commands (see above) in graphic mode. Optional arguments are listed between parenthesis.

Note that the graphic mode is automatically turned on whenever a graphic command is used, unless the variable VESA is set to "OFF".

InitGraph ("mode")

Turn on VESA graphics. The origin is on the upper-left corner of the screen (0 0). VESA graphics may hang some computers under Windows 95. Run MrBatch with the -v option to avoid such problems.

You can request a specific video mode if you use the parameter "mode" This parameter is optional: if you do not specify any value, the video mode will be taken from the first field of the VESA-Modes variable.

Valid modes are :

The VESA-Modes variable lists the video modes supported by your hardware.

Example: InitGraph "640x480"


Close VESA graphic mode and go back to text mode.

DrawBar x-pos y-pos width height color

VESA graphics. Draw a filled bar of the given size and colors.

DrawWindow x-pos y-pos width height (bg-color (bar-color)) ("title" (title-color))

VESA graphics. Draw a window of the given size and colors. The background color defaults to LightGray and the title-bar color defaults to Blue. If you include a title string and a color, this text will be displayed in the title bar.

Drawtext x-pos y-pos "text" (fg-color)

VESA graphics. Draw the text string at the given position with a transparent background. The color defaults to text foreground color.

DrawGif "gif-filename" (x-pos y-pos (color-strategy))

VESA graphics. Load the given GIF-87a file and draw it on the screen. The file can be interlaced, but must be in GIF-87a (not GIF-89a). The image size should fit in the selected video mode. You cannot load a 1024x768 GIF file when you selected a 640x480 mode. The GIF position defaults to the top left corner of the screen (0 0).

The color-strategy defines the allocation of colors in the palette when more than 256 colors are needed (for instance when two 256 colors GIF files are displayed simultaneously):

The default strategy is Best-Colors.

Security-related commands

This section lists commands that help you authenticate a user. Optional arguments are listed between parenthesis.

Some of these functions cooperate with a Security gateway, that you should first install. See the section on Special TFTP servers for more infos.

GetPasswd (variable (max-length))

Same as Input, but echo stars instead of the typed characters.

Crypt "text" "salt" variable

Apply the Unix crypt function to the given 8-chars text and store the resulting crypted string into variable. The "salt" is usually a two-character string that will be found as the first two characters of the crypted string.

Note that Unix crypt is a one-way function. It is not possible to decode the crypted string. One can only try to crypt another string with the same salt and compre the resulting crypted string.

DESCrypt "text" "key" variable

Crypt the given text using the given 8-chars key and store the result as an hexadecimal string in variable.

DESDecrypt "hexcode" "key" variable

Decrypt the given hexadecimal string using the given 8-chars key and store the result in variable.

MD5 "text" variable

Compute the MD5 checksum of the given text and store it as an hexadecimal string in variable. Can be used as an alternative to the Unix crypt function to check for passwords bigger than 8 characters.

CheckUser "user" "password" "domain"

Connect to the $Security-Gateway and check if the given user exist in the given radius domain and uses the specified password. If the domain is "Unix", use the Unix user/password definition on the security gateway. For any other domain, use the security gateway domain definition file to determine the real Radius or NT domain to check.

Set the value of $Security-Check to "PASSED" or "FAILED". The password do not transit in clear on the network.

Disk-related commands

This section lists commands for preparing the hard-disk. Optional arguments are listed between parenthesis.

GetPartitions variable (disk)

Read the partition table(s) for the given disk and store it as a string into the given variable. The result string is a space-separated list of Type:Size, where

See SetPartitions for more informations about partitions.

SetPartitions "partitions" (disk)

Setup the partition table(s) to the content of the string. The format used is the same that for GetPartitions. This command also reset all boot flags (hint: use SetBootPart).

The main partition table in the master boot record (MBR) has only four entries. Moreover, DOS and Windows accept only ONE FAT partition (called the Primary partition, C:) in the main partition table. Any supplemental FAT partition should be nested in an extended partition (and is thus called a Logical partition). If we give numbers 1-4 to the partitions described in the MBR partition table and numbers 5-8 to the partitions described in the first extended partition, the definition of two FAT partitions would work by defining partition 1 as FAT, partition 2 as EXT and partition 5 as FAT. Partitions 3,4,6,7 and 8 should be marked as UNUSED. The same scheme can be used recursively to define more than two FAT partitions: nesting another extended partition in partition 6 and adding a logical FAT partition in partition 9.

In the most strict interpretation of DOS specifications, that means that entries 3 and 4 of the partition tables are never used. In practice, some versions of DOS and some other OS are able to use more than two partitions per partition table, but there is no clear rule. On this side, BpBatch is rather flexible in its interpretation of partition tables, it can often understands things that OSes cannot.

One universal rule is that there should never be more than one extended partition per partition table, otherwise the partition numbering scheme breaks down.

If you want to try funny configurations, make your own experiments, but don't complain if the OS does not recognize your partitions. The only way it is guarantee to work is to use the primary partition to store the OS boot partition, and to nest all other partitions, one at a time, in extended partitions.

Example of extended partitions :

        SetPartitions "BIGDOS:100 EXT:400 EMPTY EMPTY BIGDOS:400"

GetBootPart variable (disk)

Get the partition number with the boot flag turned on (DOS says: the activated primary partition) and store it to the variable. The first partition is numbered 1. If no partitions has the boot flag turned on, answers zero.

SetBootPart partition (disk)

Set the boot flag to the given partition. The boot flag let the master boot record (MBR) choose which partition to boot on. The first partition is numbered 1.

Blank partition (disk)

Fill the given partitions with zeroes. Can take quite a lot of time for big partitions. Do not format the partition for any operating system. See also Clean.

Clean partitions (disk) ("label")

Fast-format the given partition(s) according to the type declared in the partition table. If a label is given and the filesystem supports it, setup the partition label. For a paranoiac full format, call Blank on the partition first.

Clean is supported for (FAT16) BIGDOS, FAT32, EXT, LINUX-EXT2 and LINUX-SWAP partitions. To clean the master boot record (MBR), use Clean 0.

Clean should be used on data partitions and on MBR/EXT partitions. It is totally useless to clean a partition before unzipping a filesystem on it using FullUnzip.

FullUnzip "full-archive" partition (disk)

Decompress a full disk archive to the given partition, overwriting any existing file (clean-up on the fly).

FullUnzip is supported for (FAT16) BIGDOS, FAT32 and LINUX-EXT2.

This commands turn on VESA graphics to display a progress banner, unless VESA has been turned OFF.

IncrUnzip "incr-archive" "destpath"

Decompress an incremental disk archive to the given path. Files in the archive replace those with the same name on the target path, but other files are not deleted.

IncrUnzip is supported for (FAT16) BIGDOS, FAT32 and LINUX-EXT2. This command is far less efficient than FullUnzip since the existing filesystem structure must be preserved. However, it avoids multiplying the number of different disk images by storing the differences only.

FileUnzip "source-filename" "dest-filename"

Uncompress a file previously compressed with MrZip FileZip command. The file is validated by a 32-bits CRC.

Copy "source-filename" "dest-filename"

Copy the source file to the destinaton file, byte-to-byte. Can be used after a FullUnzip for instance to update configuration files from the server without rebuilding the image. Better to use FileUnzip for big and easy-to-compress files.

Append "src-filename-1" "src-filename-2" "dest-filename"

Copy the first, then the second file to the destination file, byte-to-byte. Can be used on arbitrary large files. The destination file cannot be one of the two source files.

Patch "source-filename" "dest-filename" ("prefix" ("postfix"))

Read the source file and perform variable substitution before writing it to the destination file. The interpretation of characters above ASCII 127 depends on the value of $IsoLatin.

By default, variables are recognized when prefixed by "${" and postfixed by "}". This can be changed to any other non-empty string. remember that if you want to use a dollar sign within the prefix or suffix, you must escape it or it will get macro-evaluated. For instance, if you want to explicitely use the default prefix and postfix, use:

        Patch "source-file" "dest-file" "\${" "}"

MkDir "path"

Recursively create directories from the root to the given full path. If the path already exists, this command has no effect.

Delete "filename", Del "filaname"

Remove the given file. The file must exist.

DelTree "path"

Recursively remove all files and directories under the given path, and remove the directory itself.

Boot commands

This section lists commands for continuing the boot process. Optional arguments are listed between parenthesis.


Restore the memory and the interrupt vectors allocated by the bootprom. All attempts to make TFTP transfers will fail after calling this command. It is usually a good idea to call this command before HdBoot, or you might run short of memory under DOS/Windows. This command is implicitely called by FloppyBoot.

Note that although this function restore all vectors "officially" rerouted by the BootProm, it does not seems to restore everything. But it works well enough for DOS and Windows.

LoadRamDisk "ramdisk-filename"

Load a floppy disk image into the extended memory and redirect the BIOS Disk Services to make floppy disk calls use this image instead. This command implicitely calls HideBootProm. Call FloppyBoot to boot on the ramdisk you just loaded.

This kind of ramdisk may not be as robust as what you get when you use the TFTPBoot command. The only advantage is that it only steals a few hundred bytes of conventional memory instead of the >64 KB reserved by the TCP/IP BootPROM. Warning, nothing secures the extended memory in which the ramdisk resides. There is no way to uninstall such a ramdisk.

LoadZRamDisk "ramdisk-filename"

Do the same as LoadRamDisk, but for an image that has been compressed using MrZip FileZip command. Compressed ramdisks are protected against data corruption (and uncomplete download) by a byte count and a 32-bits CRC.

TFTPBoot "remote-bootfile"

Chain to another boot file (for instance a floppy image made with InCom's BpShell program). See the file referencing conventions for accessing a file on another TFTP server.


Hide the Boot ROM, load the floppy disk boot sector and boot on it.

HdBoot (disk)(:partition)

Load the given boot sector and boot from it. The disk default to zero, the first hard disk, and the partition defaults to zero, ie. the master boot record. You can boot from any partition, but be warned that Windows 95 may not let you boot a partition that has not been set as the boot partition (hint: use SetBootPart).

This command does not implicitely call HideBootProm, so you might want to call it before.

LinuxBoot "kernelfile" ("command-line" ("ramdisk-file"))

Load the given kernel and ramdisk into the high memory, setup the command line and boot the kernel. It is a good idea to put at least a minimal command line with the location of the root filesystem (like "root=dev/hda1"/). If you are using a linux system that heavily relies on lilo (like RedHat Linux 5.1), it may be necessary to add to the command line something like BOOT_IMAGE=linux. Note that the kernel can be loaded by TFTP (automatically cached on the hard disk) or directly from the target root partition.

This command works for small and big kernels (zImage and bzImage).

National language support

This section lists commands related not national language support. Optional arguments are listed between parenthesis.

RemapKeys "original-keys" "remapped-keys"

National keyboard support. Remap given keys to other characters. For instance, to swap the Y and Z keys, use

        Remapkeys "yzYZ" "zyZY"
It is a good idea to use the quoted octal notation when using characters not included in the minimal ASCII character set, in order to avoid a dependency to the iso-latin modal settings.

For international keyboards, there are two keys that produce a backslash in non-remapped (US) mode. Each of them can be independantly remapped, thanks to the fact that BpBatch sees one of them as a key answering ASCII code 252 (octal) or ASCII code 335 (octal) when shifted.

If you send me a sample script that does keyboard mapping for your national keyboard, I will make it available under To help you make your own keyboard mapping, I suggest pressing all special keys without remapping the keyboard and writing down the character they produce. These will be the original-keys. The remapped-keys simply are the key you would have liked to see, in the same order. If some keys (either original or remapped) produce characters above ASCII dec 127, use the quoted octal notation. You can easily get the octal code for any given character by looking in the ASCII table of HelpPC for instance (HelpPC is a shareware hypertext on-line help program by David Jurgens).

RemapAltkeys "original-keys" "remapped-keys"

National keyboard support. Remap the given keys when ALT is depressed For instance, to map Alt-2 to the ampersand sign, use

        RemapAltKeys "2" "@"
Note that dead keys are not supported.

LoadCodePage "cpxxx.bin"

Load and activate the given binary Codepage file. Codepages are used for the translation of Unicode characters (present on VFAT valumes for instance) into 8-bits characters. If you do not have the right Codepage loaded, you will get FAT warnings while accessing the filesystem when special characters are encountred.

All binary codepage files are available at

The default codepage is 850, a reordered superset of ISO-Latin-1. If you load a more exotic codepage, you should usually turn the variable $IsoLatin to "off" or you might get meaningless implicit conversions. Moreover, if you want to display exotic characters, you should also load the proper screen font (use "LoadFont").

LoadFont "fontfile"

Load and activate a VGA/VESA font, both in text and graphic mode. The font file must be a binary file of 16 bztes/characters (8x16 bitmap). This command can be used for National Language Support as well as for Fantasy support.

An archive with several fantasy fonts is available at This archive also contains a program to extract fonts for your codepage from the DOS .CPI file.

Commands specific to MrZip


  Source (i)archive "filename"
  Source path "path"

Set the source for the archive manipulation to the given (incremental) archive file or disk path.


  Dest (i)archive "filename"
  Dest (i)dump
  Dest path "path"

Set the destination for the archive manipulation to the given (incremental) archive file, dump or disk path. To control the quantity of data displayed during dump, use the $DumpFormat special variable.

FileZip "source-filename" "dest-filename"

Compress a file for further decompression with FileUnzip or for using as ZRamDisk. The file is validated by a 32-bits CRC.


  Filter -"pattern"
  Filter +"pattern"

Avoid/allow files and directories matching the given pattern (wildcards allowed) to be included in the archive. The pattern is matched agains the full pathname. By default, all files are included in the image. You only need to explicitely allow files that where cancelled by a filter. Each negative filter has its own positive filter (allowed) sublist.

For DOS/Windows images, you will typically use

        Filter -"*.swp"
        Filter -"temp/*"
and for Unix images, you will typically use
        Filter -"var/log/*"
        Filter -"tmp/*"


Start the archive manipulation operation, according to source, destination and filter settings. Except in a few circumstances, you will probably use the shortcut below instead of explicitely calling CopyArchive. One circumstance in which you will use CopyArchive explicitely is when you want to change the fragmentation of an image, as follow:

        set FragmentSize="30 MB"
        Source archive "original.imz"
        Dest archive "refragmented.imz"

FullZip "path" "full-archive"

Shortcut for

                Source path "path"
                Dest archive "full-archive"
You should usually first setup filters.

IncrZip "path" "incr-archive"

Shortcut for

                Source path "path"
                Dest iarchive "incr-archive"

FullDump "full-archive"

Shortcut for

                Source archive "full-archive"
                Dest dump

IncrDump "incr-archive"

Shortcut for

                Source iarchive "incr-archive"
                Dest dump

XCopy "srcpath" "dstpath"

Shortcut for

                Source path "srcpath"
                Dest path "dstpath"

5.2 NoBreak.sys

Nobreak.sys is a very small (about 350 bytes only) driver that you include at the beginning of your config.sys. Its goal is to secure the boot process, until the user is logged in. DOS provides a setting for this (namely BREAK=OFF), but it is not drastic enough, and has almost no effect in the autoexec.bat. Our driver works by modifying the scan-code of the key pressed when a break is requested, directly at the BIOS level. This way, no program at all can receive a break until break is enabled again.

The driver must be loaded from the config.sys (or using the devlod program from Undocumented DOS). Afterwards, break can be enabled by sending Yes to the NOBRK pseudo-device, and disabled again by sending No (in fact, only the first character, Y or N is significant).

As this driver relies on the BIOS, it does only work for DOS and Windows 3.1. Windows 95 has its own low-level keyboard handling routines.

Assembler source code is available.

6. Special TFTP Servers

As the only network support available in the TCP/IP BootPROM is TFTP, there is a special interest in enhancing TFTP servers for providing new capabilities.

6.1 Incom Enhanced TFTP Server

InCom GmbH distributes with the TCP/IP BootPROM an enhanced TFTP server that can send packets of up to 1408 bytes instead of the standard 512 bytes. This is a great enhancement that you should use. This server is available on the TCP/IP Bootprom Utility disk for Solaris, Windows and as Netware NLM.

6.2 Linux Enhanced TFTP Server

We built a modified version of Linux TFTP server that acts as InCom enhanced TFTP server. Basically, we simply changed the packet size from 512 to 1408 bytes and the port from 69 to 59. It is available from

6.3 The Security Gateway

We wrote a special TFTP server that serves as security gateway for authenticating users. This server runs under Linux or Solaris, and can authenticate users according to a Unix password database (NIS and shadow passwords are supported), a Windows NT (or Samba) server or a Radius server. It is available from, with source and precompiled binaries. The precompiled binaries do not include NT password encryption as we cannot distribute libdes but compilation is straightforward.

In order to use the security gateway, you just have to setup a trivial security domains configuration file that describes to which authentication server each logical security domains maps (the Unix domain implicitely maps to the server Unix password database). This is a sample configuration file:

# STFTPD configuration file
# This file specify the server of the "security domains". Two types of 
# authentication servers are supported : radius or winnt (winnt includes
# NT Server and Samba)
# Format of radius servers 
# radius        <domain>        <serveraddress>         <secret>
# secret is the secret word as specified in your /etc/raddb/clients file
# Format of SMB servers
# winnt         <domain>        <serveraddress>         <netbiosname>
# netbiosname is the NETBIOS name of your server 
# Examples
radius         sec-dom-rad     radiusserver    testing123
winnt          sec-dom-nt1     NTSERVER1
winnt          sec-dom-smb     samba           SAMBA1

Note that if you are using Samba, you must set security = user.

You can also provide to the security server a file containing a list of users which are not allowed to log on (for which the check will fail anyways).

6.4 The Broadcast TFTP Server

We wrote a special TFTP server that implements a home-made Broadcast variant of TFTP. Using this server, we were able to download images to 25 clients on a heavily loaded 10 Mb ethernet network at 6 Mb/s (it is more efficient than the regular TFTP because it does not need to acknowledge each packets). This server runs under Linux or Solaris. It is available from, with source and precompiled binaries.

As the TCP/IP bootprom does not support this protocol, our solution consist in booting a tiny ramdisk-based linux system using the tools described in this document, and running the Linux version of MrBatch which has built-in support for Broadcast TFTP. A simple batch file can the download all files to the cache in a few minutes, simultaneously on all client computers. You do not need to install Linux yourself to use this package, except if you have exotic hardware and cannot directly use the kernel provided in the package.

The process works as follow. First, you startup the broadcast server manually, giving the number of expected client computers as argument (remember, this procedure is not to be used every day but only when you changed an image and want to ensure it is immediately uploaded to all your client computers). Then, you turn on all client computers, which will run the following BpBatch script:

# This batch is run by bpbatch to launch a mini-linux using an initial 
# ramdisk, which will then run mrbatch under linux.
# The broadcast TFTP protocol only works with the Linux implementation of
# mrbatch, because of the lack of broadcast support in the bootprom itself.
# 1. Setup a tiny partition, to let a lot of space for the cache
setpartitions "BIGDOS:50"
# 2. Clean the MBR
clean 0
# 3. Run a Linux Kernel with initrd (Initial Ramdisk) supprt, and use 
#    bcastrd.gz as the initial ramdisk (will be mounted root and then
#    executed via /linuxrc). See initrd.txt for more details about
#    initial ramdisks. You don't have to specify a root device (second
#    parameter is null) to the kernel, it will use the initial ramdisk.
linuxboot "linux.krn" "" "bcastrd.gz"
# 4. The initial ramdisk will run dhcpcd to setup networking using DHCP.
#    It will then run mrbatch -w bcastlx

The initial ramdisk contains: All programs are statically linked and stripped, to avoid which is really huge. The resulting ramdisk is Gzipped and takes less than 300 KB. The kernel itself takes 450 KB (with many network cards and initrd support). When Linux is up and running, MrBatch is called with the following script (that you should edit for your needs):

# This file is executed when mrbatch is launched by the initial ramdisk
# bcastrd.gz
# It's main purpose is to "broacast copy" files to the cache
# 1. Be verbose
# 2. Don't want a "press a key"
set pauselog="OFF"
# 3. Set partitions at their final values. 
#    Important: Since you will copy files into the cache to be used in future
#    boot, you need to specify the same partitions as in the future boots.
setpartitions "BIGDOS:1024"
# 4. Clean the CACHE partition
clean -1
# 5. And the copy files into the cache, using the Broadcast TFTP protocol
#    (port 99)
# You can use the script "as is", but you surely need to modify the following
# line ! In our example, we download the file mblinux.imz, which is the image
# file for our installation of Linux.
copy "$BOOTP-Server-IP@99:mblinux.imz" "{:-1}mblinux.imz"

When the transfer is done, you can simply turn off all client computers and change their initial boot script to your favorite menu.