If you are running a HDFS service with HA enabled, you can manually cause the active NameNode to failover to the standby NameNode. This is useful for planned downtime—for hardware changes, configuration changes, or software upgrades of your primary host.

1. Go to the HDFS service.
2. Click the Instances tab.
3. Click Federation and High Availability.
4. Locate the row for the Nameservice where you want to fail over the NameNode. (Multiple rows display only when using HDFS Federation.)
5. Select Actions > Manual Failover. (This option does not appear if HA is not enabled for the cluster.)
6. From the pop-up, select the NameNode that should be made active, then click Manual Failover.
     Note: For advanced use only: You can set the Force Failover checkbox to force the selected NameNode to be active, irrespective of its state or the other NameNode's state. Forcing a failover will first attempt to failover the selected NameNode to active mode and the other NameNode to standby mode. It will do so even if the selected NameNode is in safe mode. If this fails, it will proceed to transition the selected NameNode to active mode. To avoid having two NameNodes be active, use this only if the other NameNode is either definitely stopped, or can be transitioned to standby mode by the first failover step.
7. When all the steps have been completed, click Finish.

Cloudera Manager transitions the NameNode you selected to be the active NameNode, and the other NameNode to be the standby NameNode. HDFS should never have two active NameNodes.

See Moving Highly Available NameNode, Failover Controller, and JournalNode Roles Using the Migrate Roles Wizard.

After your HA NameNodes are configured and started, you will have access to some additional commands to administer your HA HDFS cluster. Specifically, you should familiarize yourself with the subcommands of the hdfs haadmin command.

This page describes high-level uses of some important subcommands. For specific usage information of each subcommand, you should run hdfs haadmin -help <command>.

By default, applicable dfsadmin command options are run against both active and standby NameNodes. To limit an option to a specific NameNode, use the -fs option. For example,

To turn safe mode on for both NameNodes, run:

hdfs dfsadmin -safemode enter

To turn safe mode on for a single NameNode, run:

hdfs dfsadmin -fs hdfs://<host>:<port> -safemode enter

For a full list of dfsadmin command options, run: hdfs dfsadmin -help.

Converting a HA configuration from using an NFS-mounted shared edits directory to Quorum-based storage involves disabling the current HA configuration then enabling HA using Quorum-based storage.

1. Disable HA.
2. Although the standby NameNode role is removed, its name directories are not deleted. Empty these directories.
3. Enable HA with Quorum-based storage.