Install postgres in my old ubuntu system

Install postgres in my old ubuntu system: 12.04 (precise) (based on the introduction at http://www.postgresql.org/download/linux/ubuntu/)

1, Create a new file at the following location:

cd /etc/apt/sources.list.d/
sudo vi pgdg.list

2, Add this line to above file:

deb http://apt.postgresql.org/pub/repos/apt/ precise-pgdg main)

3, Execute:

wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc |   sudo apt-key add -
sudo apt-get update

sudo apt-get install postgresql-9.4 pgadmin3