title: Prometheus error starting web server: address already in use
body: <p>Need help, after starting Prometheus I get below error running in CentOS: </p>
  
  <pre><code>msg="Error starting web server, exiting gracefully" err="listen tcp 0.0.0.0:9090: bind: address already in use"
  level=info ts=2017-11-29T07:16:05.523067725Z caller=main.go:384 msg="See you next time!"
  level=info ts=2017-11-29T07:16:05.523216386Z caller=targetmanager.go:87 component="target manager" msg="Stopping target manager..."
  level=info ts=2017-11-29T07:16:05.523247638Z caller=targetmanager.go:99 component="target manager" msg="Target manager stopped"
  level=info ts=2017-11-29T07:16:05.523257989Z caller=manager.go:455 component="rule manager" msg="Stopping rule manager..."
  level=info ts=2017-11-29T07:16:05.52326427Z caller=manager.go:461 component="rule manager" msg="Rule manager stopped"
  level=info ts=2017-11-29T07:16:05.523271345Z caller=notifier.go:483 component=notifier msg="Stopping notification handler..."
  </code></pre>