agaric-coop/box/docs/extras/ruby.md

Ruby is used for many different purposes, but with Drupal, it is most often used as part of a toolset for Front End development or certain CI tasks.

Drupal VM includes built-in support for Ruby—all you need to do is make sure ruby is listed in the list of installed_extras inside config.yml before your provision Drupal VM.

Installing gems

To install ruby gems, you can add them to the list of ruby_install_gems in config.yml.

ruby_install_gems:
  - sass
  - compass

For a list of available role variables, see the geerlingguy.ruby Ansible role's README.