Copy$ rbenv install 2.1.2 ruby-build: definition not found: 2.1.2 You can list all available versions with `rbenv install --list'. If the version you're looking for is not present, first try upgrading ruby-build. If it's still missing, open a request on the ruby-build issue tracker: https://github.com/sstephenson/ruby-build/issues (Fun fact: Recent versions of ruby-build will give you a more helpf