Launching the Hadoop DataNode
Understanding the DataNode
The DataNode is a slave node in the Hadoop cluster and is responsible for storing and managing the data blocks. It communicates with the NameNode to report the list of available blocks and receive instructions for data replication and block management.
Starting the DataNode
To start the DataNode, follow these steps:
- Format the DataNode storage directory:
hdfs datanode -format
- Start the DataNode service:
hadoop-daemon.sh start datanode
You can verify that the DataNode is running by checking the web interface at http://localhost:9864
.
Configuring the DataNode
The DataNode configuration is stored in the $HADOOP_HOME/etc/hadoop/hdfs-site.xml
file.
Here's an example configuration:
<!-- hdfs-site.xml -->
<configuration>
<property>
<name>dfs.data.dir</name>
<value>/path/to/datanode/data</value>
</property>
</configuration>
This configuration sets the location of the DataNode data directory.
Monitoring the Hadoop Cluster
You can monitor the Hadoop cluster using the web interfaces provided by the NameNode and DataNode:
- NameNode web interface:
http://localhost:9870
- DataNode web interface:
http://localhost:9864
These interfaces provide information about the cluster status, running jobs, and resource utilization.
Congratulations! You have now successfully launched the Hadoop NameNode and DataNode services. With this knowledge, you can start building and running your Hadoop-based applications.