title: Delete all elasticsearch indices directly without curl
body: <p>I am starting elasticsearch, and getting the error:</p>
  
  <pre><code>java.lang.IllegalStateException: unable to upgrade the mappings for the index [[documents/xOOEXQB-RzGhQp7o7NNH9w]]
      at org.elasticsearch.cluster.metadata.MetaDataIndexUpgradeService.checkMappingsCompatibility(MetaDataIndexUpgradeService.java:172) ~[elasticsearch-5.5.0.jar:5.5.0]
  </code></pre>
  
  <p>I am not exactly sure what caused this to happen.  I did do a 
  <code>brew upgrade elasticsearch</code> but I didn't note down the last version.  I am currently on elasticsearch 5.5.</p>
  
  <p>I would like to just clear away all the mappings/indices for elasticsearch.  I don't need these data as it is for testing.  Most of the documentation says to use </p>
  
  <pre><code>curl -XDELETE 'http://localhost:9200/_all'
  </code></pre>
  
  <p>However, localhost:9200 isn't reachable (it was previously), presumably because elasticsearch cannot be properly started so it is a bit of chicken and egg.</p>
  
  <p>Is there a way for me to clear away all elasticsearch data manually?</p>