sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ $(lsb_release -cs)-pgdg main" > /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 upgrade

sudo apt-get install postgresql-9.4

sudo service postgresql stop

 * Stopping PostgreSQL 9.3 database server  [ OK ]
 * Stopping PostgreSQL 9.4 database server  [ OK ]
 * Stopping PostgreSQL 9.5 database server  [ OK ]