Install PostgresQL on Ubuntu 16.04

• Install

    $ sudo apt-get update
    $ sudo apt-get install postgresql postgresql-contrib
  

• Switch to postgres user

   $ sudo -i -u postgres
  

• Create root account

    createuser --interactive
  

  Input root, as superuser

• Create root database for user root

    createdb root
  

• Alter root’s password

    psql
    alter user root with encrypted password 'toor'
  

Now you can access to PostgreSQL by root and password toor