https://community.cloudera.com/t5/Support-Questions/ambari-agent-connection-refused-after-host-reboot/m-p/241212#M203016 <P><A rel="noopener noreferrer noopener noreferrer noopener noreferrer noopener noreferrer noopener noreferrer noopener noreferrer" href="http://xn--adrin%20gil-n7a/" target="_blank"><EM>@Adrián Gil</EM></A><EM> <BR /></EM></P><P><EM>What values do you have in<STRONG> /etc/host</STRONG>?</EM></P><P><EM>Can you share a redacted version of your /etc/hosts and the output of </EM></P><P><EM><BR /></EM></P><PRE><EM>$ hostname -f</EM></PRE><P><EM>The below shows that you are trying to change to a value which is no different from the older value <span class="lia-unicode-emoji" title=":slightly_smiling_face:">🙂</span></EM></P><PRE><EM><STRONG>Detail: Key (host_name)=(bigdata.es) already exists.</STRONG> at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2161) &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1890) &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)&nbsp; <STRONG>ERROR: duplicate key value violates unique constraint</STRONG> "uq_hosts_host_name" &nbsp;&nbsp; Detail: Key (host_name)=(bigdata.es) already exists. Error Code: 0&nbsp; Call: UPDATE hosts SET host_name = ? WHERE (host_id = ?)bind =&gt; [2 parameters bound]</EM></PRE><P><EM>Please revert </EM></P><P><BR /></P> Mon, 27 May 2019 21:36:08 GMT Shelton 2019-05-27T21:36:08Z