If you need to burn dvd’s in command line, you can use growisofs:

• to burn on the fly:
  growisofs -Z /dev/hdd=/dev/hdb -use-the-force-luke=notray -use-the-force-luke=tty -use-the-force-luke=dao -speed=4 -overburn
• to burn a previous iso file:
  growisofs -Z /dev/hdd=/tmp/xpto.iso -use-the-force-luke=notray -use-the-force-luke=tty -use-the-force-luke=dao -speed=4 -overburn
• erase dvd-rw:
  growisofs -Z /dev/dvd=/dev/zero

You can adjust speed, but some medias don’t support speeds above 2