# first, create a sparse image
minus_size=$(($size * 6 / 100))
size=$(($size - $minus_size))
- dd if=/dev/zero of=$img bs=1M count=1 seek=$(($size - 1))
+ dd if=/dev/zero of=$img bs=1M count=1 seek=$size
# fill in the partition table
parted -s "$img" "mklabel msdos"