rbenv
Groom your app’s Ruby environment
...Override the Ruby version anytime: just set an environment variable. Rock-solid in production. Your application's executables are its interface with ops. With rbenv and Bundler binstubs you'll never again need to cd in a cron job or Chef recipe to ensure you've selected the right runtime. The Ruby version dependency lives in one place—your app—so upgrades and rollbacks are atomic, even when you switch versions.