Greetings boris90210,

Good thinking -- it would be cool!
Sorry, KNOPPIX needs a whole disk.
But even if you used a RW-DVD this
can't be done -- at leat to date.
Reading and wrting to part of a disk
is called "packet" writing and is still
expermintal in Linux.

I have experimented with a 2CD version
that uses regular KNOPPIX in one CD
and a second CDRW. On boot up
from a floppy, the CDRW is automatically
added to the desktop and can even add some simple
new programs. A new CD (the whole thing)
is then written when you have any changes
to save.
http://www.knoppix.net/docs/index.php/BurnHome

Best Wishes
paradocs