ActionView::Template::Error: Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true
Add to the following files in environment
test.rb / development.rb / production.rb

Rails.application.routes.default_url_options[:host] = ''

undefined method …_index_path Ruby on Rails
Your models should always be singular and controllers should always be plural

EXECJS runtime error
Download nodejs

Uninstalling ruby manually installed from source
lets say that you've installed ruby 2.4 from source... then you want to downgrade to 2.3

Go to the folder where you run "sudo make install" command then

sudo make uninstall