Using Ambari Web, browse the Hosts page.

Find and click the FQDN of the host on which the component resides.

In Components, find a decommissioned component.

If the component status is Started, stop it.

A decommissioned slave component may restart in the decommissioned state.

Click Delete from the component drop-down menu.

Deleting a slave component, such as a DataNode does not automatically inform a master component, such as a NameNode to remove the slave component from its exclusion list. Adding a deleted slave component back into the cluster presents the following issue; the added slave remains decommissioned from the master's perspective. Restart the master component, as a work-around.

To enable Ambari to recognize and monitor only the remaining components, restart services.