I reply by myself, having discovered an incredible stupid thing:
genisoimage: Missing pathspec.
Usage: genisoimage [options] -o file directory ...
Use genisoimage -help
to get a list of valid options.
Report problems to firstname.lastname@example.org.
asbesto@gemini:~$ man genisoimage
genisoimage - create ISO9660/Joliet/HFS filesystem with optional Rock
This is one of the most STUPID thing I saw on a GNU/Linux system. Not mantaining the backward compatibility with the past is a very bad thing, a very stupid choice that must be avoided when possible - and here is so simple to avoid: just a link, or two word in a mkisofs man page.
I'm really astonished about the way Open source software is going in these years!