question Re: The DataNode is not connected to one or more of its NameNode(s). in Support Questions

question Re: The DataNode is not connected to one or more of its NameNode(s). in Support Questions https://community.cloudera.com/t5/Support-Questions/The-DataNode-is-not-connected-to-one-or-more-of-its-NameNode/m-p/45199#M46134 Hello Karthi, Thanks for bringing your questions to this community.I'll start by saying that the health issues you see stem from an inability for the Cloudera Manager agents on your host/hosts to communicate with Cloudera Manager on port 7182 and for your agent to communicate with the Host Monitor (to upload metrics) on port 9995. It could be your agent is not started.  On your host or hosts, try running (as root or sudo): service cloudera-scm-agent start If you are lucky, that's all that needs to be done.  If the agents are running and you still see this problem, this gets into more complex troubleshooting.  In that case, I'd start by making sure that iptables is not restricting ports (turn it off on all hosts if it is on), try telneting or nc to the Cloudera Manager host's port 7182. All that said, you may want to walk our quickstart tutorial here: <A href="http://www.cloudera.com/developers/get-started-with-hadoop-tutorial.html" target="_blank">http://www.cloudera.com/developers/get-started-with-hadoop-tutorial.html</A> It might probe to be a good start since you are new to Cloudera and hadoop.We love that you are giving this a try so keep the questions coming. NOTE:  for troubleshooting agent issues, your best friend is the agent log; by default it is: /var/log/cloudera-scm-agent/cloudera-scm-agent.log Look for python stack traces and error messages that could help you and us diagnose the issue.By default, the agent will try to heartbeat to the server that is configured in the "server_host" configuration in the agent's configurtation file ( /etc/cloudera-scm-agent/config.ini ).  So make sure that the host is that of your Cloudera Manager and it is resolvable on this host. That's a lot, so I'll stop there.  Let us know if you get stuck. Cheers, Ben Fri, 16 Sep 2016 17:23:03 GMT bgooley 2016-09-16T17:23:03Z