Using the webhdfs:// Protocol

About this task

Before you can copy data from an HDFS cluster to a MapR cluster using the webhdfs:// protocol, you must configure the MapR cluster to access the HDFS cluster. To do this, complete the steps listed in Configuring a MapR Cluster to Access an HDFS Cluster for the security scenario that best describes your HDFS and MapR clusters and then complete the steps listed under Verifying Access to an HDFS Cluster.

To copy data from HDFS to MapR-FS using the webhdfs:// protocol, complete the following steps:

Procedure

  1. The HDFS cluster must have WebHDFS enabled. Verify that the following parameter exists in the hdfs-site.xml file and that the value is set to true. 
    <property>
<name>dfs.webhdfs.enabled</name>
<value>true</value>
</property>

    You also need the following information:

    • <NameNode>: the IP address or hostname of the NameNode in the HDFS cluster
    • <NameNode HTTP Port>: the HTTP port on the NameNode in the HDFS cluster
    • <HDFS path>: the path to the HDFS directory from which you plan to copy data
    • <MapR-FS path>: the path in the MapR cluster to which you plan to copy HDFS data
  2. Run the following command from a node in the MapR cluster to copy data from HDFS to MapR-FS using webhdfs://: 
    hadoop distcp webhdfs://<NameNode>:<NameNode HTTP Port>/<HDFS path> maprfs:///<MapR-FS path>
    For example:
    hadoop distcp webhdfs://nn2:50070/user/sara maprfs:///user/sara

    Note the required triple slashes in maprfs:///.