if your /etc/apt/sources.list file contains very few lines, fill it like below.. Note that, if you use other than intrepid, then replace them with your version of ubuntu/debian.


deb http://archive.ubuntu.com/ubuntu/ intrepid main restricted
deb-src http://archive.ubuntu.com/ubuntu/ intrepid main restricted
deb http://archive.ubuntu.com/ubuntu/ intrepid-updates main restricted
deb-src http://archive.ubuntu.com/ubuntu/ intrepid-updates main restricted
deb http://archive.ubuntu.com/ubuntu/ intrepid universe
deb-src http://archive.ubuntu.com/ubuntu/ intrepid universe
deb http://archive.ubuntu.com/ubuntu/ intrepid-updates universe
deb-src http://archive.ubuntu.com/ubuntu/ intrepid-updates universe
deb http://archive.ubuntu.com/ubuntu/ intrepid multiverse
deb-src http://archive.ubuntu.com/ubuntu/ intrepid multiverse
deb http://archive.ubuntu.com/ubuntu/ intrepid-updates multiverse
deb-src http://archive.ubuntu.com/ubuntu/ intrepid-updates multiverse
deb http://archive.ubuntu.com/ubuntu/ intrepid-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ intrepid-backports main restricted universe multiverse
deb http://archive.canonical.com/ubuntu intrepid partner
deb-src http://archive.canonical.com/ubuntu intrepid partner
deb http://archive.ubuntu.com/ubuntu/ intrepid-security main restricted
deb-src http://archive.ubuntu.com/ubuntu/ intrepid-security main restricted
deb http://archive.ubuntu.com/ubuntu/ intrepid-security universe
deb-src http://archive.ubuntu.com/ubuntu/ intrepid-security universe
deb http://archive.ubuntu.com/ubuntu/ intrepid-security multiverse
deb http://archive.ubuntu.com/ubuntu/ intrepid-proposed restricted main multiverse universe
deb-src http://archive.ubuntu.com/ubuntu/ intrepid-security multiverse