General :: Resize 100MB Fat Filesystem To Shrink It From 100MB To 50 MB?

I'd like to share with you an experiment. look at following steps: create an empty file with a low level tool like "dd"

# dd if=/dev/zero of=fatimage bs=512 count=200K

we now have an about 100MB zeroed file.

format it with mkdosfs (FAT16)

# mkdosfs fatimage

now we have a 100MB fat filesystem. We could check it with dosfsck. Mount it on loop, and copy saome data in it, so that it have a percentage of used space of about 30% (I've tried to copy on it a 30MB data directory). Then umount it.

# mount -o loop -t auto fatimage mountpoint
# cp -a $data mountpoint
# umount mountpoint

check filesystem with dosfscheck. We can notice used clusters and verify bytes used on that filesystem. And we could evalutate a space amuont to shrink the filesystem... why? Just for a didactical test. we could decide to shrink our 100MB filesystem to 50 MB: we have about 30 MB of data cpied on it, so there wil be anout 70 MB of free space. How to resize 100MB fat filesystem to shrink it from 100MB to 50 MB? If I had used an ext2/3 (or ext4 too but I don't know it) or a ntfs filesystem, I would easly been able to shrink it with resize2fs or ntfsresize. But as regards Fat filesystem I don't know any tool that work just on the filesystem.

I've tried, fatresize, but It return a strange error... searching for I suspect it is deeply based on parted and it expects to work on a partition not only on a filesystem like that described above. So is there anyone who knows, which tool I could use to shrink that filesystem? If you wolud like to make the test following above steps and tring to use fatresize program I will be grateful if you report your results there.