[Rails] rails generate scaffold - ERROR

Hi,

I just installed ROR using the rvm using these instructions:
http://ryanbigg.com/2010/12/ubuntu-ruby-rvm-rails-and-you/

Using Ubuntu 12 on VirtualBox

I'm trying to create a demo_app

rails generate scaffold User name:string email:string

gives me this error:
--
/home/natmanu/.rvm/gems/ruby-2.0.0-p247/gems/execjs-2.0.2/lib/execjs/runtimes.rb:51:in `autodetect': Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247/gems/execjs-2.0.2/lib/execjs.rb:5:in `<module:ExecJS>'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247/gems/execjs-2.0.2/lib/execjs.rb:4:in `<top (required)>'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247/gems/uglifier-2.1.1/lib/uglifier.rb:3:in `require'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247/gems/uglifier-2.1.1/lib/uglifier.rb:3:in `<top (required)>'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `require'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `each'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `block in require'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `each'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `require'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247@global/gems/bundler-1.3.5/lib/bundler.rb:132:in `require'
    from /home/natmanu/Sites/microblog/config/application.rb:7:in `<top (required)>'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands.rb:44:in `require'
    from /home/natmanu/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands.rb:44:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

Any helpers?

TIA NAT

--
You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-talk+unsubscribe@googlegroups.com.
To post to this group, send email to rubyonrails-talk@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/rubyonrails-talk/87b3b425-94f4-4988-a8d9-c90b90f325c2%40googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.