@Saurabh Verma How to change the JDK version for an existing cluster Re-run Ambari Server Setup. ambari-server setup At the prompt to change the JDK, Enter y. Do you want to change Oracle JDK [y/n] (n)? y At the prompt to choose a JDK, Enter 1 to change the JDK to v1.8. [1] - Oracle JDK 1.8 [2] - Oracle JDK 1.7 [3] - Custom JDK If you choose Oracle JDK 1.8 or Oracle JDK 1.7, the JDK you choose downloads and installs automatically on the Ambari Server host. This option requires that you have an internet connection. You must install this JDK on all hosts in the cluster to this same path. If you choose Custom JDK , verify or add the custom JDK path on all hosts in the cluster. Use this option if you want to use OpenJDK or do not have an internet connection (and have pre-installed the JDK on all hosts). After setup completes, you must restart each component for the new JDK to be used. Important You must also update your JCE security policy files on the Ambari Server and all hosts in the cluster to match the new JDK version. If you do not update the JCE to match the JDK, you may have issues starting services. Refer to the Ambari Security Guide for more information on Installing the JCE. Thanks, Matt ... View more

Hi, you need to give your Ubuntu host a domain name which you then add as the FQDN. For the second part, you need to copy your id_rsa file you created and paste it into the SSh private key box. (It is either the id_rsa or id_rsa.pub, i cant remember), as shown in the image above. ... View more