Would that work like this?

mkisofs -R -U -V "KNOPPIX.net filesystem" -P "KNOPPIX www.knoppix.net" -hide-rr-moved -cache-inodes -no-bak -pad /mnt/hda1/knx/source/KNOPPIX | nice -5 /usr/bin/create_compressed_fs -b > /mnt/hda1/knx/master/KNOPPIX/KNOPPIX