title: Is it possible to start/configure the confluent docker images with a property file instead of environment variables?
body: <p><a href="https://docs.confluent.io/current/installation/docker/docs/configuration.html" rel="nofollow noreferrer">The docs</a> state that the cp-zookeeper and cp-kafka images are configured via environment variables. </p>
  
  <blockquote>
    <p>The ZooKeeper image uses variables prefixed with ZOOKEEPER_ with the variables expressed exactly as they would appear in the zookeeper.properties file. As an example, to set clientPort, tickTime, and syncLimit run the command below:</p>
  </blockquote>
  
  <pre><code> docker run -d \
  --net=host \
  --name=zookeeper \
  -e ZOOKEEPER_CLIENT_PORT=32181 \
  -e ZOOKEEPER_TICK_TIME=2000 \
  -e ZOOKEEPER_SYNC_LIMIT=2
  confluentinc/cp-zookeeper:3.3.1
  </code></pre>
  
  <p>I would prefer to provide a <code>zookeeper.properties</code> (server.properties for kafka) instead of specifying the ZOOKEEPER_* (KAFKA_*) environment variables. Is this somehow possible? </p>
  
  <p>In my current setup with "non-confluent" kafka I simply mount a config volume containing the properties on /etc/kafka and then start kafka with that, but looking at the <a href="https://github.com/confluentinc/cp-docker-images" rel="nofollow noreferrer">confluent docker images</a> I can see that this won't work since there's some special templating-magic going on in order to generate the properties inside the container.</p>