Since almost all the commercial DVD movies come with pre-encrypted by default (a folk of DRM, digital right management), if you just copy and paste the content, then you won't be able to play the content nonetheless.
And since in a DVD video disk, within the container format, usually there are several audio files embedded into it (different languages, different tracks with different audio channels, subtitles, etc) other than using a dedicated app like the Shrinkta, backing up a DVD to hard drive properly with selected audio files only, etc, is not possible.
Also, by extracting the content you want will reduce the overall output file size dramatically as well. Let's have a look at some of the,
*. Very easy to use (written using GTK+ and Python) interface.
*. Extract/Backup selected portions of the DVD movie disk such as - Selected chapters.
*. Choose preferred audio channels - DTS/AC3, etc.
*. Opt-out certain languages.
*. Excellent help file (I humbly advice you to read it first).
*. Has the ability to make the DVDs region free (another locking/encrypting mechanism).
*. Both single and dual layer supported.
*. Can burn the data to DVD disk using the assigned CD/DVD burning application.
*. Shrink video files under given size.
*. No subtitle extracting available (my only complaint).
Remember it can be illegal to create a backup of your DVD into hard disk or any other media depending on your country. But if you've purchase them within your region or country, then it is most certainly legal, as long as you don't "share" (as far as I know, but I advice you to do your own research :D).
Anyhow, you can install Shrinkta in Ubuntu 11.04 Natty Narwhal by entering the below command in your GNU/Linux command line.
sudo apt-get install shrinkta
That should do it. Good luck.