Follows the steps below to play DVD in your ubuntu 9.10 karmic Koala
1. Become root
$ sudo su –
2. Add medibuntu repositories to your sources.list.
# wget http://www.medibuntu.org/sources.list.d/karmic.list –output-document=/etc/apt/sources.list.d/medibuntu.list
Now add the GPG Key:
# apt-get update && sudo apt-get install medibuntu-keyring && sudo apt-get update
3.Update your system.
# apt-get update
4. Now install the libdvdcss library.
# apt-get install libdvdcss2
# cd /usr/share/doc/libdvdread4/
# ./install-css.sh