助けが必要。ruby (レールではありません) でスクリプト化され、capybara-webkit gem が使用されます。EC2 と Linode の両方で確認しましたが、このエラーは解決しません。
webkit_server: cannot connect to X server
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/driver/webkit/connection.rb:103:in attempt_connect'
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/driver/webkit/connection.rb:96:inconnect'
/usr/lib/ruby/1.8/timeout.rb:62:in timeout'
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/driver/webkit/connection.rb:94:inconnect'
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/driver/webkit/connection.rb:17:in initialize'
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/driver/webkit.rb:26:innew'
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/driver/webkit.rb:26:in initialize'
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/webkit.rb:5:innew'
/usr/lib/ruby/gems/1.8/gems/capybara-webkit-0.12.1/lib/capybara/webkit.rb:5
/usr/lib/ruby/gems/1.8/gems/capybara-1.1.2/lib/capybara/session.rb:61:in call'
/usr/lib/ruby/gems/1.8/gems/capybara-1.1.2/lib/capybara/session.rb:61:indriver'
/usr/lib/ruby/gems/1.8/gems/capybara-1.1.2/lib/capybara/session.rb:157:in visit'
/usr/lib/ruby/gems/1.8/gems/capybara-1.1.2/lib/capybara/dsl.rb:161:invisit'
ありがとうございました