If you'd rather use your CD-ROM for installing packages or updating your system automatically with APT, you can put it in your sources.list.
Open up your terminal and type following command to add CD-ROM to your sources.list file
Continue Reading... Open up your terminal and type following command to add CD-ROM to your sources.list file
sudo apt-cdrom add
source:http://linuxpoison.blogspot.com/2011/01/13578167751510.html