custom image

dd if=/dev/zero of=freedos.img bs=1M count=30
parted freedos.img

(parted) mklabel msdos
(parted) mkpart primary fat16 2048s 100%
(parted) set 1 boot on
(parted) quit

sudo kpartx -av freedos.img
# take note of the loopback device
mkfs.msdos -F 16 -n FREEDOS /dev/mapper/loop0p1
# add syslinux bootloader
syslinux -i /dev/mapper/loop0p1
# mount it
mkdir /media/freedso && mount /dev/mapper/loop0p1 /media/freedos
# add syslinux loader and config
cp cp /usr/lib/syslinux/bios/{chain.c32,ldlinux.c32,libcom32.c32,libutil.c32} /media/freedos
# get a freedos image
wget http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.0/fdboot.img
# loopmount so we can copys stuff
mkdir /media/source && mount fdboot.img /media/source
cp /media/source/{command.com,kernel.sys} /media/freedos/
# add a config.sys (it's C for a memdisk)
echo 'SHELL=C:\COMMAND.COM' > /media/freedos/config.sys
# add a syslinux.cfg
default fdos
prompt 1
timeout 3

label fdos
	menu label fdos
	com32 chain.c32
	append freedos=/kernel.sys