Start postgres server downloaded from ruby gem on ubuntu

Question

When I run rake:db migrate from my rails app, I get this output:

rake aborted!
PG::ConnectionBad: could not connect to server: Connection refused
Is the server running on host "localhost" (127.0.0.1) and accepting
TCP/IP connections on port 5432?

/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:888:in `initialize'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:888:in `new'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:888:in `connect'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:568:in `initialize'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:41:in `new'
 /home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:41:in `postgresql_connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:435:in `new_connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:445:in `checkout_new_connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:416:in `acquire_connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:351:in `block in checkout'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:350:in `checkout'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:265:in `block in connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:264:in `connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:541:in `retrieve_connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_handling.rb:113:in `retrieve_connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/connection_handling.rb:87:in `connection'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/migration.rb:910:in `initialize'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/migration.rb:807:in `new'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/migration.rb:807:in `up'
 /home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/migration.rb:785:in `migrate'
/home/ubuntu/.rvm/gems/ruby-2.1.2/gems/activerecord-4.1.4/lib/active_record/railties/databases.rake:34:in `block (2 levels) in <top (required)>'
/home/ubuntu/.rvm/gems/ruby-2.1.2/bin/ruby_executable_hooks:15:in `eval'
/home/ubuntu/.rvm/gems/ruby-2.1.2/bin/ruby_executable_hooks:15:in `<main>'

In my gemfile I have

gem 'pg'

and in my database.yml I have

default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5

development:
  <<: *default
  database: fake_lunch_hub_development

test:
  <<: *default
  database: fake_lunch_hub_test


production:
  <<: *default
  database: fake_lunch_hub_production
  username: fake_lunch_hub
  password: <%= ENV['FAKE_LUNCH_HUB_DATABASE_PASSWORD'] %>

This setup used to connect to the database perfectly, but I did a lot of refactoring and renaming (the project is no longer called fake_lunch_hub) and I moved the project off of my local machine (mac) and onto an amazon EC2 instance (ubuntu).

There are many other questions on Stackoverflow that offer solutions using psql, but when I run the command

psql

I get this:

The program 'psql' can be found in the following packages:
* postgresql-client-common
* postgres-xc-client
Try: sudo apt-get install <selected package>

I'd rather not download a new postgres package because I already have it successfully downloaded from the gem.

How can I get that server started and accepting connections?

EDIT:

FULL SOLUTION:

sudo apt-get install postgres
sudo su
su postgres
createuser ubuntu
createuser fake_lunch_hub
createdb fake_lunch_hub
exit
exit
rails server

resolves the issues

Answer 1

The gem is just a way for Ruby/Rails to talk to a Postgres server. The gem itself does not contain its own server.

You'll still need to install one:

sudo apt-get install postgresql