https://community.cloudera.com/t5/Support-Questions/ambari-agent-connection-refused-after-host-reboot/m-p/241207#M203011 <P><A rel="noopener noreferrer noopener noreferrer" href="http://@Adri%C3%A1n%20Gil" target="_blank">@Adrián Gil</A></P><P>Changing the hostname <STRONG>/etc/hosts</STRONG> is not enough there are the below step you MUST perform to have your Cluster working again. In<STRONG> Ambari Web &gt; Dashboard, stop all services</STRONG>.</P><P>Stop ambari-server and ambari-agents on all hosts.</P><PRE># ambari-server stop # ambari-agent stop</PRE><P>Create a file host_names_changes.json file with hostnames changes.</P><P>Contents of the <STRONG>host_names_changes.json</STRONG></P><PRE>{ &nbsp; "bigdata" : { &nbsp; &nbsp; &nbsp; "old_name_here" : "bigdata-es" &nbsp; } }</PRE><P>From the directory where you saved the above file as a root user run </P><PRE># ambari-server update-host-names host_names_changes.json</PRE><P><BR /></P><P>After successful execution, your ambari will update all the necessary files except the old hostnames in ambari.properties change the below values </P><P><BR /></P><P>Change these 3 values in <STRONG>/etc/ambari-server/conf/ambari.properties</STRONG></P><PRE>server.jdbc.rca.url= server.jdbc.url=jdbc= server.jdbc.hostname=</PRE><P>You will need to change also values for hive,oozie etc change according to your installation</P><P><STRONG># Hive</STRONG></P><PRE>grant all privileges on hive.* to 'hive'@'bigdata-es' identified by 'hive_password'; grant all privileges on hive.* to 'hive'@'bigdata-es' with grant option;</PRE><P><STRONG># Oozie</STRONG></P><PRE>grant all privileges on oozie.* to 'hive'@'bigdata-es' identified by 'oozie_password'; grant all privileges on oozie.* to 'hive'@'bigdata-es' with grant option;</PRE><P><STRONG># Ranger</STRONG></P><PRE>grant all privileges on ranger.* to 'hive'@'bigdata-es' identified by 'ranger_password'; grant all privileges on ranger.* to 'hive'@'bigdata-es' with grant option;</PRE><P><STRONG># Rangerkms</STRONG></P><PRE>grant all privileges on rangerkms.* to 'hive'@'bigdata-es' identified by 'rangerkms_password'; grant all privileges on rangerkms.* to 'hive'@'bigdata-es' with grant option;</PRE><P><BR /></P><P>After doing the above now you can restart amabri and the ambari-agent hoping you have changed to the name in ambari-agent.ini, </P><P>Start ambari-server and ambari-agents on all hosts.</P><PRE># ambari-server start # ambari-agent start</PRE><P>Before running the Ambari component startall make sure hive,oozie,ranger etc have the correct hostname in the Ambari UI Configs !!</P><P>Happy Hadooping</P><P><BR /></P> Fri, 24 May 2019 22:02:32 GMT Shelton 2019-05-24T22:02:32Z