(or flash BIOS without floppy or Windows OR CD-ROM)
This can be done!!! :o)
I have a PC with no floppy & no CD-ROM, it is running Sarge and has a second (empty) hard disk.
I needed to boot in DOS so I could flash the BIOS.
Add this to grub's config ( /boot/grub/menu.lst - I instinctively type vi etc because it's a config file, then realise it's in /boot/grub because it's for booting and needs to be in the boot partition (if that's partitioned)) :
title ["FreeDOS"] Image root (hd1,0) kernel /memdisk initrd (hd1,0)/fdos1440.img
Download: Memdisk:
http://syslinux.zytor.com/memdisk.php (I got the newest one out of the SysLinux 3.07 download - http://www.kernel.org/pub/linux/utils/boot/syslinux/syslinux-3.07.tar.gz although if you apt-get install syslinux you get one too /usr/lib/syslinux/memdisk which you could use, but that's currently 2.11-0.1 or so)
DOS floppy image:
http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/beta9sr1/fdos1440.img
In Linux use fdisk (or cfdisk as I did) to create a small partition at the start of the empty disk (I did ["8MB"])
Device Boot Start End Blocks Id System /dev/hdc1 * 1 1 8001 b W95 ["FAT32"]
Use dosfstools mkfs.vfat to format the new partition:
apt-get install dosfstools mkfs.vfat /dev/hdc1
mount it:
mkdir /mnt/hdc1 mount /dev/hdc1 /mnt/hdc1
copy memdisk and fdos1440.img and the flash program which you download from your hardware vendor into it:
boot, choose ["FreeDOS"] Image, Choose 1:
1->["FreeDOS"] (speedup, 386+)
Then choose 1:
1) ["FreeDOS"] Beta9 ServiceRelease1 [2004-November-30]
Then choose 2:
2. ["FreeDOS"] Safe Mode (skip driver loading)
...and you should now find yourself at a nice little A:\>_ prompt :o)
C: dir
then there you are :o) You can now flash your BIOS because you are in native DOS.
I'm wondering if you can use a loopback file within Linux as the root filesystem too, so you don't need a disk partition, now THAT would be scarey!!! :o)
This guy needed a CD-ROM:
(wimp!)