When maintaining a Hadoop cluster, you will need to restart various service from time-to-time when/if you update Hadoop configurations.
I ran into a problem today with Ambari where I wanted to do a rollling restart of all of my DataNodes, but when I clicked on the “Restart DataNodes” entry in the “Restart” drop down the dialog indicated “There are no DataNodes to do rolling restarts”.
![](https://www.ryanchapin.com/wp-content/uploads/ambari_qa_incorrect_dn_restart_dialog.png)
This was clearly incorrect.
![](https://www.ryanchapin.com/wp-content/uploads/ambari_qa_datanode_restart_alert.png)
It did not take me too long to figure out that I had already put HDFS into Maintenance Mode. As a result, Ambari does not see that there are any DataNodes that need to be restarted.
Taking HDFS out of Maintenance mode allowed me to then execute a rolling restart through Ambari.