$ bundle exec rails c
include Rails.application.routes.url_helpers
root_url
ArgumentError: Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true
from /home/zunda/local/src/mastodon/vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/http/url.rb:62:in `full_url_for'
ほむ