I can not play all DVD's on my DVD ROM. I was told that I need to install codes for VLC. You should be able to do this via the Terminal, I am not shore of the command string to use.
sudo apt-get install vlc codes is not working. Do you perhaps know ?
You probably need libdvdcss which is usually not available by default on Debian (and Debian-like) distributions.
Start with just vlc if you haven't and see if it brings everything it needs:
sudo apt-get install vlc
If not, try also installing the following:
sudo apt-get install libdvdread4 libdvdnav4 libdvd-pkg