There are a gazillion HOWTOs out there for flashing a BIOS image without having to resort to ugly "boot DOS from floppy" or "run Windows *.exe file from BIOS vendor" and other ugly stuff. Unfortunately, the proposed solutions are equally ugly (e.g. creating custom CD-ROMs which contain the "floppy" with DOS/Windows flash tools).
Folks, this is so much simpler than you think:
The flashrom tool (GPL'd, written for LinuxBIOS purposes, but works perfectly fine with proprietary BIOSes, too) will easily do what you want, on a running Linux system. No floppy crap, no CD-ROM crap, no DOS/Windows crap, no rebooting crap.
$ apt-get install flashrom
Detect whether flashrom knows about your chipset/mainboard/BIOS chip:
Read the BIOS image into a file:
$ flashrom -r backup.bin
Write a BIOS image (proprietary or LinuxBIOS) on the ROM chip:
$ flashrom -wv newbios.bin
WARNING: This will overwrite your current BIOS! Make sure you know what you're doing!
For the Debian-challenged, flashrom is available in source form too, of course:
$ svn co svn://linuxbios.org/repos/trunk/util/flashrom $ cd flashrom $ make
The list of supported chipsets, mainboards, and ROM chips is limited of course, but it's constantly expanding. Contact us on the LinuxBIOS mailing list if you want other hardware supported (or even better: if you have patches!). In many cases adding support for new hardware is pretty easy...