flashing the BIOS of a floppy-less system using Linux

How to boot dos on a floppy-less system and flash the BIOS

This short guide assumes that your system is capable of booting over the network via PXE. If your motherboard/NIC does not support PXE, there are other, older network booting protocols you can investigate. If you are unable to boot over the network, you can almost certainly use some of the steps below to build a bootable USB memory stick.

Beware!

The method described below makes no provision for saving a copy of your current BIOS. If you are desperate to have a backup copy of your current BIOS, I suggest you create a USB stick (good luck!) and boot from that.

Here's the method I used to do it:

On a Linux system:

obtain and compile pxegrub. Make sure you compile in support for ethernet hardware of the system who's BIOS you want to update.
pxegrub is a part of "grub", which can be found here. Depending on your hardware, you may need "nbgrub" instead of "pxegrub". See the grub website for more information. Here is a compiled "pxegrub" that supports the Realtek 8139 driver.
install and configure dhcpd. See dhcpd.conf for a sample config file. You must enter the MAC-address of the system whose BIOS you want to flash. Make sure you include the "option T150 code 150 = string;" and the "ddns-update-style ad-hoc;" magic.
install and configure tftp. You must supply at least one path to a directory, otherwise the daemon will not allow any transfers. Following the dhcpd config file above, the path would be "/path/to/tftp/download/area".
obtain a FreeDOS bootfloppy image. I used
http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/beta9sr1/disksets/1440KB/B9BOOT01.IMG.
you can also get it from this server.
create a working copy of the bootfloppy image, called, for example, "freedos-boot-fd.img".
mount the floppy image under Linux using a loopback device:
mkdir /bf
mount -o loop=/dev/loop1 /path/to/image /bf
delete some files to make space for your BIOS image:
cd /bf/special
rm testdisk.exe debug.com edit.exe xcopy.exe
edit /bf/fdconfig.sys to load himem.exe.
find the line: "13459?!DEVICE=A:\DRIVER\HIMEM.EXE" and change it to: "123459?!DEVICE=A:\DRIVER\HIMEM.EXE".
below it add "DOS=HIGH".
copy your flash program and flash image somewhere within this filesystem.
copy "memtest" from the boot-floppy to your tftp download area.
cp /bf/memdisk /path/to/tftp/download/area
unmount the floppy image.

create a grub config file. See here for a sample file. More or less you need 1 entry:

timeout=10
default=0

title FreeDOS
	kernel /path/to/tftp/download/area/memdisk
	initrd /path/to/tftp/download/area/freedos-boot-fd.img

You should now be ready to boot your client. Assuming the boot is successful, you should get the "grub" boot menu. Select FreeDOS and hit return.

you should see:

Welcome to the FreeDOS MetaKern boot menu
Please type a digit to select a list item
or type A or C to reboot from A: or C:...
Using <1> if no choice after 10s.
Boot sectors:
1 -> FreeDOS	(speedup, 386+)
2 -> FreeDOS	(chain to kernel  .sys!)

Hit "2" here.

Now you should see:

FreeDOS Beta9 ServiceRelease1 (2004-November-30) INSTALLATION

1. Install to harddisk using FreeDOS SETUP (default)
2. FreeDOS Safe Mode  (skip driver loading)

9. Run setup with user-specified storage driver(s)

Enter a choice: [01234569]

Hit "2" here too. You should have an "A:\>" prompt. Go to whereever you put your flash program and image and flash BIOS.