echo "deb http://apt.postgresql.org/pub/repos/apt/ precise-pgdg main" | sudo tee -a /etc/apt/sources.list.d/pgdg.list
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
sudo apt-get update
sudo apt-get install postgresql-contrib-9.1 postgresql-server-dev-9.1 postgresql-9.1-postgis-2.1 postgresql-9.1-postgis-2.1-scripts