How to get PostgreSQL to work - ruby-on-rails

Question

I recently deployed a heroku app and it gave me an error that sqlite3 isn't supported so I made a new project using the rails new -d postgresql project_name command. And everything worked (it currently has a stable version that people can access on the web), until I added a scaffold: rails g scaffold Projects and then went into the routes.rb and added , :only [:index, :show] and then ran the server. Which worked until I loaded the home page, then I got the error:
PG::ConnectionBad (could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
):
There are similar questions on here, but they are usually erroring on Heroku's side, while this is just being run locally.
What is causing this error?
Fun fact: /var/run/postgresql/ isn't a directory I have.
EDIT:
OS: Ubuntu on an Oracle VM
The full console response:
PG::ConnectionBad (could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
):
pg (1.0.0) lib/pg.rb:56:in `initialize'
pg (1.0.0) lib/pg.rb:56:in `new'
pg (1.0.0) lib/pg.rb:56:in `connect'
activerecord (5.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:697:in `connect'
activerecord (5.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:221:in `initialize'
activerecord (5.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:38:in `new'
activerecord (5.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:38:in `postgresql_connection'
activerecord (5.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:759:in `new_connection'
activerecord (5.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:803:in `checkout_new_connection'
activerecord (5.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:782:in `try_to_checkout_new_connection'
activerecord (5.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:743:in `acquire_connection'
activerecord (5.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:500:in `checkout'
activerecord (5.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:374:in `connection'
activerecord (5.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:931:in `retrieve_connection'
activerecord (5.1.6) lib/active_record/connection_handling.rb:116:in `retrieve_connection'
activerecord (5.1.6) lib/active_record/connection_handling.rb:88:in `connection'
activerecord (5.1.6) lib/active_record/migration.rb:562:in `connection'
activerecord (5.1.6) lib/active_record/migration.rb:553:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/callbacks.rb:26:in `block in call'
activesupport (5.1.6) lib/active_support/callbacks.rb:97:in `run_callbacks'
actionpack (5.1.6) lib/action_dispatch/middleware/callbacks.rb:24:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/executor.rb:12:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/debug_exceptions.rb:59:in `call'
web-console (3.6.2) lib/web_console/middleware.rb:135:in `call_app'
web-console (3.6.2) lib/web_console/middleware.rb:30:in `block in call'
web-console (3.6.2) lib/web_console/middleware.rb:20:in `catch'
web-console (3.6.2) lib/web_console/middleware.rb:20:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/show_exceptions.rb:31:in `call'
railties (5.1.6) lib/rails/rack/logger.rb:36:in `call_app'
railties (5.1.6) lib/rails/rack/logger.rb:24:in `block in call'
activesupport (5.1.6) lib/active_support/tagged_logging.rb:69:in `block in tagged'
activesupport (5.1.6) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (5.1.6) lib/active_support/tagged_logging.rb:69:in `tagged'
railties (5.1.6) lib/rails/rack/logger.rb:24:in `call'
sprockets-rails (3.2.1) lib/sprockets/rails/quiet_assets.rb:13:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/remote_ip.rb:79:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/request_id.rb:25:in `call'
rack (2.0.5) lib/rack/method_override.rb:22:in `call'
rack (2.0.5) lib/rack/runtime.rb:22:in `call'
activesupport (5.1.6) lib/active_support/cache/strategy/local_cache_middleware.rb:27:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/executor.rb:12:in `call'
actionpack (5.1.6) lib/action_dispatch/middleware/static.rb:125:in `call'
rack (2.0.5) lib/rack/sendfile.rb:111:in `call'
railties (5.1.6) lib/rails/engine.rb:522:in `call'
puma (3.11.4) lib/puma/configuration.rb:225:in `call'
puma (3.11.4) lib/puma/server.rb:632:in `handle_request'
puma (3.11.4) lib/puma/server.rb:446:in `process_client'
puma (3.11.4) lib/puma/server.rb:306:in `block in run'
puma (3.11.4) lib/puma/thread_pool.rb:120:in `block in spawn_thread'
The database.yml:
# PostgreSQL. Versions 9.1 and up are supported.
#
# Install the pg driver:
# gem install pg
# On OS X with Homebrew:
# gem install pg -- --with-pg-config=/usr/local/bin/pg_config
# On OS X with MacPorts:
# gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
# On Windows:
# gem install pg
# Choose the win32 build.
# Install PostgreSQL and put its /bin directory on your path.
#
# Configure Using Gemfile
# gem 'pg'
#
default: &default
adapter: postgresql
encoding: unicode
# For details on connection pooling, see Rails configuration guide
# http://guides.rubyonrails.org/configuring.html#database-pooling
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
development:
<<: *default
database: rileyshaw_development
# The specified database role being used to connect to postgres.
# To create additional roles in postgres see `$ createuser --help`.
# When left blank, postgres will use the default role. This is
# the same name as the operating system user that initialized the database.
#username: rileyshaw
# The password associated with the postgres role (username).
#password:
# Connect on a TCP socket. Omitted by default since the client uses a
# domain socket that doesn't need configuration. Windows does not have
# domain sockets, so uncomment these lines.
#host: localhost
# The TCP port the server listens on. Defaults to 5432.
# If your server runs on a different port number, change accordingly.
#port: 5432
# Schema search path. The server defaults to $user,public
#schema_search_path: myapp,sharedapp,public
# Minimum log levels, in increasing order:
# debug5, debug4, debug3, debug2, debug1,
# log, notice, warning, error, fatal, and panic
# Defaults to warning.
#min_messages: notice
# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
<<: *default
database: rileyshaw_test
# As with config/secrets.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read http://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
# DATABASE_URL="postgres://myuser:mypass#localhost/somedatabase"
#
# You can use this database configuration with:
#
# production:
# url: <%= ENV['DATABASE_URL'] %>
#
production:
<<: *default
database: rileyshaw_production
username: rileyshaw
password: <%= ENV['RILEYSHAW_DATABASE_PASSWORD'] %>

Answer 1

Add this to your Gemfile
group: production do
gem "pg"
end
group: development do
gem "sqlite3"
end
Then bundle install
gem "Pg" serves for production purpose while gem "sqlite3" can still be used locally, But I highly advise that you install and get Postgres up and running on your system to avoid future breakdown. But if you're doing a fast prototyping, then go ahead

Answer 2

it seems you didn't install postgres and didn't add proper user.
https://gorails.com/setup/ubuntu/16.04#postgresql should be your answer :)