How do I install PostgreSQL 9.6 on any Ubuntu version?

For the following Ubuntu versions, you can install with the given commands, as per the official PostgreSQL Apt Repository.

Ubuntu 17.04 - 17.10

Version 9.6 comes with the distribution.

sudo apt-get install postgresql-9.6

Ubuntu 14.04, 16.04

sudo add-apt-repository "deb http://apt.postgresql.org/pub/repos/apt/ $(lsb_release -sc)-pgdg main"
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
sudo apt-get update
sudo apt-get install postgresql-9.6

Follow below steps:

Reference is taken from this blog.

You need to add the latest PostgreSQL repository for the latest version.

sudo add-apt-repository "deb https://apt.postgresql.org/pub/repos/apt/ trusty-pgdg main"

Update and Install PostgreSQL 9.6:

sudo apt-get update
sudo apt-get install postgresql-9.6

Default postgres super user and postgres database is created. You need to set a password for the postgres super user.

ubuntu@:~$ sudo passwd postgres
Enter new UNIX password:****
Retype new UNIX password:****
passwd: password updated successfully

If service is not started, you can start the PostgreSQL service.

sudo service postgresql start

Connect PostgreSQL server using postgres user:

ubuntu@:~$ su postgres
Password:****

Create a sample database:

createdb database_name

Connect to that database:

psql -d database_name

I followed this Github gist - I am running ubuntu xenial inside vagrant and wanted to upgrade existing postresql official repository vesion 9.5 to 9.6 so that I can use PostGIS extension which is served best by version 9.6 (officially mentioned in their site) Hope this helps someone.