How do I compare a file with a floppy image and the actual floppy's content? Is there a command that compares a floppy disk image (e.g. a .iso file) to the actual contents of the floppy the image was written on (e.g. /dev/fd0)?

A floppy device file is a file. Any command that reads files will work on it.


cmp /dev/fd0 image.fat


Pass the `-l` option if you want a list of all differing bytes; for human consumption, this is mostly useful in the form


cmp -l /dev/fd0 image.fat | wc -l


to know how many bytes differ. Run `cmp -s /dev/fd0 image.fat` if you don't want any output, just a return status of 0 if the two files are identical and 1 if they're different.

This compares the images byte by byte. If the floppy and the image contain files and you only want to compare the files and not the metadata (file dates, etc.) nor the empty space, mount the floppy and the image and compare the directory trees.