На этот вопрос уже есть ответ здесь:

Я создал новое приложение rails в папке 'проблемы' и когда я хотелрубин с ' Я получил ошибку. Любая помощь будет высоко ценится

[thiago@netbox issues]$ rails s
/home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/execjs-1.4.0/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/thiago/.rvm/gems/ruby-1.9.3-p429/gems/execjs-1.4.0/lib/execjs.rb:5:in `'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/execjs-1.4.0/lib/execjs.rb:4:in `'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/coffee-script-2.2.0/lib/coffee_script.rb:1:in `require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/coffee-script-2.2.0/lib/coffee_script.rb:1:in `'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/coffee-script-2.2.0/lib/coffee-script.rb:1:in `require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/coffee-script-2.2.0/lib/coffee-script.rb:1:in `'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/coffee-rails-3.2.2/lib/coffee-rails.rb:1:in `require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/coffee-rails-3.2.2/lib/coffee-rails.rb:1:in `'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `each'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `block in require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `each'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429@global/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429@global/gems/bundler-1.3.5/lib/bundler.rb:132:in `require'
    from /home/thiago/Documents/wdi/rails_practice/issues/config/application.rb:7:in `'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.13/lib/rails/commands.rb:53:in `require'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.13/lib/rails/commands.rb:53:in `block in '
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.13/lib/rails/commands.rb:50:in `tap'
    from /home/thiago/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.13/lib/rails/commands.rb:50:in `'
    from script/rails:6:in `require'
    from script/rails:6:in `'

Я добавил 'therubyracer» драгоценный камень в мой Gemfile, а затем$ bundle install ' Работает!

Gemfile
source 'https://rubygems.org'

gem 'rails', '3.2.8'
gem 'sqlite3'

group :assets do
gem 'sass-rails',   '~> 3.2.3'
gem 'coffee-rails', '~> 3.2.1'
gem 'uglifier', '>= 1.0.3'
end

gem 'jquery-rails'
gem 'therubyracer' # added