title: How to use startup_script_file in Packer
body: <p>I can not understand how to use startup_script_file in Packer. In <a href="https://www.packer.io/docs/builders/googlecompute.html" rel="nofollow noreferrer">documentation</a> I read this:</p>
  
  <blockquote>
    <p>A startup script can be provided via the startup_script_file or 'startup-script' instance creation metadata field.</p>
  </blockquote>
  
  <p>But without an example, it tells me not that much. I do not know whether I can do it like so in my configuration file (inside builders block):</p>
  
  <pre><code>"metadata" {
      "startup_script_file": "path to file"
  }
  </code></pre>
  
  <p>Or should I use it like so:</p>
  
  <pre><code>$ packer build -startup_script_file 'path to file' config.json
  </code></pre>
  
  <p>If I can set it inside my configuration file, should I set something else in provisioners block to make it work? Unfortunatelly, documentation says too little about this and does not provide any example. At least, I could not find it.</p>