The HDP Stack is the coordinated set of Hadoop components that you have installed on hosts in your cluster. Your set of Hadoop components and hosts is unique to your cluster. Before upgrading the Stack on your cluster, review all Hadoop services and hosts in your cluster to confirm the location of Hadoop components. For example, use the Hosts and Services views in the Ambari Web UI, which summarize and list the components installed on each Ambari host, to determine the components installed on each host. For more information about using Ambari to view components in your cluster, see Working with Hosts, and Viewing Components on a Host.
Complete the following procedures to upgrade the Stack from version 2.0 to version 2.1 on your current, Ambari-installed-and-managed cluster.
![[Note]](../common/images/admon/note.png) | Note |
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If you plan to upgrade your existing JDK, do so after upgrading Ambari, before upgrading the Stack. |
