We're deploying with cap and using a script that send USR2 to the unicorn process to reload and it usually works but every once in a while it will fail. When that happens looking in the unicorn log reveals that it's looking for a Gemfile in an old release directory that no longer exists. Exception : /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.0.21/lib/bundler/definition.rb:14:in `build': /var/ww