title: What is happening when using ../ with docker-compose volume
body: <p>I am having problems with writing files out from inside a docker container to my host computer. I believe this is a privilege issue and prefer not to set <code>privileged: True</code>. A work around for writing out files is by pre-pending <code>../</code> to a volume in my <code>docker-compose.yml</code> file. For example,</p>
  
  <pre><code>version: '3'
  services:
      example:
          volumes:
           - ../:/example
  </code></pre>
  
  <p>What exactly is <code>../</code> doing here? Is it taking from the container's privileges and "going up" a directory to the host machine? Without <code>../</code>, I am unable to write out files to my host machine.</p>