/usr/lib/ruby/vendor_ruby/rails/generators/rails/app/templates/config/boot.rb is in ruby-railties 2:4.2.6-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)
require 'bundler/setup' # Set up gems listed in the Gemfile.
|