cdrecord -scanbus will show device id info to be used with the following command

cdrecord -blank=disk dev=4,0,0 erases the entire disk

cdrecord -v -sao speed=4 dev=4,0,0 filename.iso will burn a DVD
-v turns on verbose mode
-sao session at once

mkisofs -o cd.iso cdtest will create an iso image file cd.iso and populates it with files from cdtest.

mount cd.iso /mnt/iso -o loop mounts the just created filesystem

k3b is a GUI tool
dvdbackup
DVDShrink