How to build a filesystem image from scratch

dd-mkdosfs.sh

#!/bin/bash # requires mtools package
dd if=/dev/zero of=test.img bs=1M count=2
mkdosfs test.img
mdir -i test.img
echo "Hello" > simple.txt
mcopy -i test.img simple.txt ::/simple.txt
mmd -i test.img stuff
mdir -i test.img stuff
rm simple.txt
mcopy -i test.img ::/simple.txt simple.txt