Ambari not start after downgrade

[#1]

I tried to upgrade HDP from 2.4.2 to 2.5.3 and encountered an error "There is no active namenodes". The problem is described here namenode-restart-fails-during-hdp-upgrade

So I decided to do Downgrade and increase the timeout. However, after the downgrade Ambari doesn't start because of "DB configs consistency check failed." I guess the bag is Downgrade Can Create Multiple Mappings For Latest Configs

Recovery from backup failed.

How can I solve this problem?

HDP-2.4.2.0 
Ambari 2.4.0.1 
Postgres 8.4.20

From ambari-server-check-database.log

ERROR - You have config(s), in cluster development, that is(are) selected more than once in clusterconfigmapping table: ams-env,webhcat-log4j,ranger-site,ranger-ugsync-site,ranger-admin-site,admin-properties,ranger-hive-policymgr-ssl,ranger-env,hcat-env,hive-site,ranger-hive-plugin-properties,webhcat-site,hive-exec-log4j,ams-log4j,webhcat-env,ams-ssl-server,hiveserver2-site,ams-hbase-log4j,hive-log4j,ams-ssl-client,ams-hbase-policy,ams-grafana-ini,ams-hbase-security-site,hive-env,ams-grafana-env,usersync-properties,ranger-hive-security

[#2]

@Alena Melnikova

There are some issues reported related to the error that you are getting. Those errors usually occurs when we try to downgrade ambari.

Those issues are fixed in ambari 2.5 so i will suggest you to upgrade to ambari 2.5 instead of downgrading as it has many additional fixes including [1]. The instructions for Ambari upgrade to 2.5.0.3 is available here: http://docs.hortonworks.com/HDPDocuments/Ambari-2.5.0.3/bk_ambari-upgrade/content/ambari_upgrade_gui...

.

[1] Downgrade Can Create Multiple Mappings For Latest Configs: https://issues.apache.org/jira/browse/AMBARI-19130

[#3]

@Jay SenSharma

Hi Jay,

Thanks for your answer.

I thought about upgrade Ambari to 2.5, but how can I do it if my current ambari-server does not even start? So I can't accomplish prerequisites such as:

• Ensure all services in the cluster are running.
• Run each Service Check (found under the Service Actions menu) and confirm they execute successfully.
• Clear all alerts, or understand why they are being generated. Remediate as necessary.
• etc