/usr/lib/ruby/vendor_ruby/ is in ruby-daemons 1.1.9-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/daemons/
/usr/lib/ruby/vendor_ruby/daemons/pid.rb
/usr/lib/ruby/vendor_ruby/daemons/pidmem.rb
/usr/lib/ruby/vendor_ruby/daemons/etc_extension.rb
/usr/lib/ruby/vendor_ruby/daemons/cmdline.rb
/usr/lib/ruby/vendor_ruby/daemons/change_privilege.rb
/usr/lib/ruby/vendor_ruby/daemons/daemonize.rb
/usr/lib/ruby/vendor_ruby/daemons/pidfile.rb
/usr/lib/ruby/vendor_ruby/daemons/exceptions.rb
/usr/lib/ruby/vendor_ruby/daemons/monitor.rb
/usr/lib/ruby/vendor_ruby/daemons/controller.rb
/usr/lib/ruby/vendor_ruby/daemons/application.rb
/usr/lib/ruby/vendor_ruby/daemons/application_group.rb
/usr/lib/ruby/vendor_ruby/daemons.rb