Install the Rails Gem:
jruby —S gem install rails
You should see the following output, which tells you that six Gems and their documentation have been installed:
JRuby limited openssl loaded. gem install jruby-openssl for full support. http://wiki.jruby.org/wiki/JRuby_Builtin_OpenSSL Successfully installed activesupport-2.1.1 Successfully installed activerecord-2.1.1 Successfully installed actionpack-2.1.1 Successfully installed actionmailer-2.1.1 Successfully installed activeresource-2.1.1 Successfully installed rails-2.1.1 6 gems installed Installing ri documentation for activesupport-2.1.1... Installing ri documentation for activerecord-2.1.1... Installing ri documentation for actionpack-2.1.1... Installing ri documentation for actionmailer-2.1.1... Installing ri documentation for activeresource-2.1.1... Installing RDoc documentation for activesupport-2.1.1... Installing RDoc documentation for activerecord-2.1.1... Installing RDoc documentation for actionpack-2.1.1... Installing RDoc documentation for actionmailer-2.1.1... Installing RDoc documentation for activeresource-2.1.1...
The -S parameter that you used to run the command to install Rails tells JRuby to look for the script anywhere in the <JRUBY_HOME> path.