ruby - "rails generate rspec:install" fails -

i'm trying run rails generate rspec:install error. i'm using ruby 2.0.0p353 , rails 4.0.3.

the error is:

/home/adminuser/.rvm/gems/ruby-2.0.0-p353/gems/execjs-2.0.2/lib/execjs/runtimes.rb:51:in autodetect': not find javascript runtime. see https://github.com/sstephenson/execjs list of available runtimes. (execjs::runtimeunavailable) /home/adminuser/.rvm/gems/ruby-2.0.0-p353/gems/execjs-2.0.2/lib/execjs.rb:5:in' /home/adminuser/.rvm/gems/ruby-2.0.0-p353/gems/execjs-2.0.2/lib/execjs.rb:4:in <top (required)>' /home/adminuser/.rvm/gems/ruby-2.0.0-p353/gems/uglifier-2.4.0/lib/uglifier.rb:3:inrequire' /home/adminuser/.rvm/gems/ruby-2.0.0-p353/gems/uglifier-2.4.0/lib/uglifier.rb:3:in <top (required)>' /home/adminuser/.rvm/gems/ruby-2.0.0-p353@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:inrequire' /home/adminuser/.rvm/gems/ruby-2.0.0-p353@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in block (2 levels) in require' /home/adminuser/.rvm/gems/ruby-2.0.0-p353@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:ineach' /home/adminuser/.rvm/gems/ruby-2.0.0-p353@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in block in require' /home/adminuser/.rvm/gems/ruby-2.0.0-p353@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:ineach' /home/adminuser/.rvm/gems/ruby-2.0.0-p353@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in require' /home/adminuser/.rvm/gems/ruby-2.0.0-p353@global/gems/bundler-1.3.5/lib/bundler.rb:132:inrequire' /home/adminuser/desktop/667-workspace/assignment_3/config/application.rb:12:in <top (required)>' /home/adminuser/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.3/lib/rails/commands.rb:43:inrequire' /home/adminuser/.rvm/gems/ruby-2.0.0-p353/gems/railties-4.0.3/lib/rails/commands.rb:43:in <top (required)>' bin/rails:4:inrequire' bin/rails:4:in `'

you need install either therubyracer or nodejs in order run rails generators. prefer nodejs, cause can used in other cases such bower or npm