Booting floppy images without having a real floppy drive can be handy for example when updating the BIOS or maybe even installing operation systems.

First get memdisk which is part of syslinux (also in the debian-package syslinux: dpkg -L syslinux grep memdisk). memdisk is a small driver which emulates a disk in the RAM.

Then configure GRUB to take memdisk as kernel and the floppy image as initrd. memdisk and the floppy images need to be accessed by grub, so put them in /boot.

A sample GRUB configuration is:

title Upgrade BIOS
root (hd0,0)
kernel /memdisk
initrd /1KUJ09US.IMG