If you want to first copy the DVD to the hard drive for quicker access, use the script dvdbackup or the utility vobcopy.
If the DVD is 4.7GB or less (i.e. not a dual layer), you can simply make a copy of the DVD:
$ growisofs -Z /dev/dvdrw -dvd-compat -V”MY_DVD_TITLE” -dvd-video /path/to/dvdimage
/path/to/dvdimage should contain AUDIO_TS and/or VIDEO_TS directories.
If the DVD is more than 4.7GB (i.e. a DVD-9), it will have to be split and/or transcoded to DVD-5 size (4.7GB) or smaller.