you can do it with vobcopy -->
http://vobcopy.org
or with mplayer -->
http://www.mplayerhq.hu
or with cpdvd -->
http://www.lallafa.de/bp/cpdvd.html
each of them works different - with vobcopy you can create a copy of the whole structure of the DVD
as well as with cpdvd - which has not worked as well for me
mplayer can play dvds - and dump them to disk as well as encode them to different formats - like avi or VCD
try these tools - and read the manuals on how to operate them...