title: How to detect a docker daemon port
body: <p>I have installed Ubuntu and Docker. I am trying to launch Raik container:</p>
  
  <pre><code>$ DOCKER_RIAK_AUTOMATIC_CLUSTERING=1 DOCKER_RAIK_CLUSTER_SIZE=5 DOCKER_RIAK_BACKEND=leveldb make start-cluster ./bin/start
  </code></pre>
  
  <p>and get the error message:</p>
  
  <blockquote>
    <p>It looks like the environment variable DOCKER_HOST has not been set. 
    The Riak cluster cannot be started unless this has been set
    appropriately.  For example:</p>
    
    <p>export DOCKER_HOST="tcp://127.0.0.1:2375"</p>
  </blockquote>
  
  <p>If I set </p>
  
  <pre><code>export DOCKER_HOST="tcp://127.0.0.1:2375"
  </code></pre>
  
  <p>all my other containers stop working and said, that can not find the Docker daemon.</p>
  
  <p>It looks like my Docker damon use other than 2375 port.  How can I check it ?</p>