当我调用bundle exec ssh它工作正常.
但是当我调用bundle exec cap部署时,我得到以下跟踪：

$cap deploy
    triggering start callbacks for `deploy'
  * 18:42:19 == Currently executing `multistage:ensure'
*** Defaulting to `preprod'
  * 18:42:19 == Currently executing `preprod'
  * 18:42:19 == Currently executing `deploy'
  * 18:42:19 == Currently executing `deploy:update'
 ** transaction: start
  * 18:42:19 == Currently executing `deploy:update_code'
  * 18:42:19 == Currently executing `deploy:set_prevIoUs_revision'
  * executing "cd /rails_apps/com.example.preprod/current; git rev-parse --short HEAD"
    servers: ["preprod.example.com"]
connection Failed for: preprod.example.com (NameError: uninitialized constant Net::SSH::KnownHosts::SUPPORTED_TYPE)

当然,example.com是占位符,它不是来自于capistrano配置中的错误.

有什么可能导致的想法？

我使用Ruby 1.9.3-p194的RVM.

谢谢 ！