ruby on rails - Webrick server not running -

i installed ruby 2.0.0 , ran

 gem install rails 

to install gems. installed gems properly. existing rails app, ran "bundle install" command , typed command in terminal:

 rails s 

to start webrick server.

but server failed start , getting error:

   /usr/lib/ruby/vendor_ruby/railties/lib/rails_generator/options.rb:32:in `default_options': undefined method `write_inheritable_attribute' rails::generator::base:class (nomethoderror) 

can tell why error comming? , how rails server , running? thanks.

to install rails 4.0:

gem install rails --version 4.0.0 --no-ri --no-rdoc 

http://weblog.rubyonrails.org/2013/6/25/rails-4-0-final/

note!, better ruby versions management want use rvm:

http://rvm.io/rvm/install

then install ruby:

http://rvm.io/rubies/installing

after installing rvm , ruby can switch between ruby versions with:

rvm use 1.9.3 

or other ruby version have installed, see ruby versions have, run:

rvm list 

after switching yo desired ruby version, can install rails:

gem install rails --version 4.0.0 

or rails version need.

a nice tutorial here:

http://railsapps.github.io/installing-rails.html