upgrade PostgreSQL from version 9.5 to version 9.6 without losing data Ubuntu

First we have to stop postgresql

sudo /etc/init.d/postgresql stop

Create a new file called /etc/apt/sources.list.d/pgdg.list and add below line

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

Follow below commands

wget -q -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
sudo apt-get update
sudo apt-get install postgresql-9.4
sudo pg_dropcluster --stop 9.4 main 
sudo /etc/init.d/postgresql start

Now we have everything, just need to upgrade it as below

sudo pg_upgradecluster 9.3 main
sudo pg_dropcluster 9.3 main

That's it. Mostly upgraded cluster will run on port number 5433. Check it with below command

sudo pg_lsclusters