ambari-server start On running the above command, I was encountering the same error while starting Ambari-server, where ambari failed to start the Postgresql server with error 3. I figured out the following solution to start ambari-server. You can check the status using service postgresql status This gives the status of the service running as PostgreSQL. In case this is giving the error that the service is not running and the server failed to start, you can check the reason with the following commands: systemctl status postgresql.service If the reasons show anything related to the port and the listener like: Then navigate to the following path and check the versions: ls /var/lib/pgsql In case you find other folders like 9.6 or 9.5, for example, 9.6, then try and check if postgresql-9.6 is running. service postgresql-9.6 status systemctl status postgresql-9.6.service In case you find that this is running, you will have to stop the service and chkconfig it to off. service postgresql-9.6 stop chkconfig postgresql-9.6 off Try and restart the ambari-server now and this might work, as the ambari server tries to start the postgresql using /var/lib/pgsql/data/postgresql.conf and not the 9.6 version configuration. In order to stop facilitate the server to use the default configuration, we have to stop the server on 9.6 version or point ambari to 9.6 version pgsql. ambari-server start ambari-server status ... View more