title: Successfully started Zookeeper server but failed to start broker server
body: <p>I am running Apache Kafka on my local machine (MacOS). I have the <code>bin/</code> path setup. I try to start kafka by:</p>
  <ol>
  <li><p>Step one, start Zookeeper:
  <code>zookeeper-server-start.sh kafka_2.13-3.0.0/config/zookeeper.properties</code>
  This step is successful.</p>
  </li>
  <li><p>Then, I try to start broker server by:</p>
  </li>
  </ol>
  <p><code>kafka-server-start.sh kafka_2.13-3.0.0/config/server.properties</code></p>
  <p>The broker server is not started, I see following error:</p>
  <pre><code>org.apache.kafka.common.KafkaException: Failed to acquire lock on file .lock in /Users/john/kafka_2.13-3.0.0/data/kafka. A Kafka instance in another process or thread is using this directory.
      at kafka.log.LogManager.$anonfun$lockLogDirs$1(LogManager.scala:241)
      at scala.collection.StrictOptimizedIterableOps.flatMap(StrictOptimizedIterableOps.scala:117)
      at scala.collection.StrictOptimizedIterableOps.flatMap$(StrictOptimizedIterableOps.scala:104)
      at scala.collection.mutable.ArraySeq.flatMap(ArraySeq.scala:37)
  </code></pre>
  <p>Based on the above error log, it complains that a Kafka instance in another process or thread is using this directory <code>/Users/john/kafka_2.13-3.0.0/data/kafka</code>. But I can't think of any other process using it on my Macbook.</p>
  <p>How can I figure out which process is using that directory, or how can I get rid of this error so that I can start the broker server?</p>