Frequently used commands

This section lists the commonly used commands and their options.

mmhdfs

To check the status of the NameNodes and DataNodes in the HDFS Transparency cluster, run the following command:
```
/usr/lpp/mmfs/hadoop/sbin/mmhdfs hdfs status
```
To start the DataNode, run the following command:
```
/usr/lpp/mmfs/hadoop/sbin/mmhdfs hdfs-dn start
```
To stop the DataNode, run the following command:
```
/usr/lpp/mmfs/hadoop/sbin/mmhdfs hdfs-dn stop
```

mmces

To start the HDFS Transparency NameNodes, run the following command:
```
/usr/lpp/mmfs/bin/mmces service start hdfs -a
```
Note: Do not use the mmhdfs command.
To stop the HDFS Transparency NameNodes, run the following command:
```
/usr/lpp/mmfs/bin/mmces service stop hdfs -a
```
Note: Do not use the mmhdfs command.
To check the value of the CES HDFS protocol IPs, run the following command:
```
/usr/lpp/mmfs/bin/mmces address list
```
To verify the CES HDFS service, run the following command:
```
/usr/lpp/mmfs/bin/mmces service list -a
```

mmhealth

To show the health status of the node, run the following command:
```
/usr/lpp/mmfs/bin/mmhealth node show
```
To show the NameNode health status, run the following command on the NameNode:
```
/usr/lpp/mmfs/bin/mmhealth node show HDFS_Namenode -v
```
To show the DataNode health status, run the following command on the DataNode:
```
/usr/lpp/mmfs/bin/mmhealth node show HDFS_Datanode -v
```

hdfs

To retrieve the status and check the state of all the HDFS NameNodes, run the following command:
```
/usr/lpp/mmfs/hadoop/bin/hdfs haadmin -getAllServiceState
```
To manually trigger the HDFS Transparency cluster to failover to the standby NameNode, run the following commands:
```
/usr/lpp/mmfs/hadoop/bin/hdfs haadmin -failover nn1 nn2
/usr/lpp/mmfs/bin/mmces address move --ces-ip x.x.x.x --ces-node node.example.com
```
Note: Replace the --ces-ip parameter with the CES IP address of the HDFS Transparency cluster and the --ces-node parameter with the name of the new active NameNode.

For more information on mmhdfs, mmces, and mmhealth commands, see the respective command in the IBM Storage Scale: Command and Programming Reference Guide.