HA configuration is backward compatible and works with your existing single NameNode configuration.
If you installed your cluster using Ambari, then to enable and operate with an HA Namenode you will need to disable Ambari.
On the Ambari server machine, shut down ambari server:
/etc/init.d/ambari-server stop
On the remaining HDP machines, shut down the ambari agent services:
/etc/init.d/ambari-agent server stop
Deploy the Hadoop Core RPM to the machine designated for the second NameNode. Follow the following instructions to manually deploy the Hadoop Core RPM to the second NameNode machine.
As this first step you will enable the NameNodes to share metadata through QJM. The next step is then to enable automatic failover through Zookeeper.
