explain on about the BUNDLER_GEMFILE
Tips for using Unicorn with Sandbox installation tools Since unicorn includes executables and is usually used to start a Ruby process, there are certain caveats to using it with tools that sandbox RubyGems installations such as Bundler or Isolate . General deployment If you’re sandboxing your unicorn installation and using Capistrano (or similar), it’s required that you sandbox your RubyGems in a per-application shared directory that can be used between different revisions. unicorn will stash its original command-line at startup for the USR2 upgrades, and cleaning up old revisions will cause revision-specific installations of unicorn to go missing and upgrades to fail. If you find yourself in this situation and can’t afford downtime, you can override the existing unicorn executable path in the config file like this: Unicorn::HttpServer::START_CTX = "/some/path/to/bin/un...