To manage components running on a specific host, choose a FQDN on the Hosts page. For example, choose c6403.ambari.apache.org in the default example shown. Summary-Components lists all components installed on that host.

Choose options in Host Actions, to start, stop, restart, delete, or turn on maintenance mode for all components installed on the selected host.

Alternatively, choose action options from the drop-down menu next to an individual component on a host. The drop-down menu shows current operation status for each component, For example, you can decommission, restart, or stop the DataNode component (started) for HDFS, by selecting one of the options shown in the following example: