does "dump" command knows DVD device ?

No. DUMP by itself does not know this. Dump is an old program, but it still works. However you need to pipe utput from dump ti mkisofs (to make a file that the DVD can understand). From there you can store the dump-file on hard disk to be burned ti DVD later or you could (but probably should not) pipe the output from mkisofs directly to cdburn (or another burning program that you can call from the commandline). Maybe you should think about making a .tar.bz2 file insted of dump? Say you want to backup your home dir, you could give: tar -cvfj /etc/backup.tar.gz /home/username Burn this to a DVD later.

Dump was designed to write to tape -style devices - it writes a stream of bytes. DVDs, as random-access devices, require a filesystem to be used. Therefore, the best approach I can come up with is to dump the filesystem to a file on another filesystem, and then create an ISO image from that, which is then burned to DVD with cdrecord, Gnomebaker, or other burner. This approach does require yyou to have copious disc space handy, however. An example set of commands follows to back up the hypothetical filesystem /dev/hda3: (you should be root for all of them):

mkdir /scratch/dumpstore dump 0f /scratch/dumpstore/daily_dump /dev/hda3 mkisofs -o /scratch/dump.iso /scratch/dumpstore cdrecord -sao -eject dev=2,0,0 /scratch/dump.iso

Note that you need to know the device to ue for the burner: use cdrecord --scanbus to find this out. Now, if you want to avoid using all the scratch space, it appears that both mkisofs and cdrecord can be used in a pipeline - try the following:

dump 0f - | mkisofs --stream-media-size 714000 -o - | cdrecord -pad dev=2,0,0 -

Be prepared to make a few coasters.