This tutorial explains the process of installing, configuring, and running Apache Hadoop on Clear Linux* OS.
For this tutorial, you will install Hadoop in a single machine running both the master and slave daemons.
The Apache Hadoop software library is a framework for distributed processing of large data sets across clusters of computers using simple programming models. It is designed to scale up from single servers to thousands of machines, with each machine offering local computation and storage.
Apache Hadoop is included in the big-data-basic bundle. To install the framework, enter the following command:
sudo swupd bundle-add big-data-basic
To create the configuration directory, enter the following command:
sudo mkdir /etc/hadoop
Copy the defaults from
/etc/hadoopwith the following command:
$ sudo cp /usr/share/defaults/hadoop/* /etc/hadoop
Since Clear Linux OS is a stateless system, never modify the files under the
/usr/share/defaultsdirectory. The software updater will overwrite those files.
Once all the configuration files are in
/etc/hadoop, edit them to fit your needs. The NameNode server is the master server that manages the namespace of the files’ system and regulates the clients’ access to files. The first file to be edited,
/etc/hadoop/core-site.xml, informs the Hadoop daemon where NameNode is running. In this tutorial, NameNode runs in the localhost.
/etc/hadoop/core-site.xmlfile using any editor and modify the file as follows:
<?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="configuration.xsl"?> <configuration> <property> <name>fs.default.name</name> <value>hdfs://localhost:9000</value> </property> </configuration>
/etc/hadoop/hdfs-site.xmlfile. This file configures the HDFS daemons. This configuration includes the list of permitted and excluded data nodes and the size of those blocks. For this example, set the number of block replication to 1 from the default of 3 as follows:
<?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="configuration.xsl"?> <configuration> <property> <name>dfs.replication</name> <value>1</value> </property> <property> <name>dfs.permission</name> <value>false</value> </property> </configuration>
/etc/hadoop/mapred-site.xmlfile. This file configures all daemons related to MapReduce: JobTracker and TaskTrackers. With MapReduce, Hadoop can process big amounts of data in multiple systems. In our example, we set YARN as our runtime framework for executing MapReduce jobs as follows:
<?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="configuration.xsl"?> <configuration> <property> <name>mapreduce.framework.name</name> <value>yarn</value> </property> </configuration>
/etc/hadoop/yarn-site.xmlfile. This file configures all daemons related to YARN: ResourceManager and NodeManager. In our example, we implement the mapreduce_shuffle service, which is the default as follows:
<?xml version="1.0"?> <configuration> <property> <name>yarn.nodemanager.aux-services</name> <value>mapreduce_shuffle</value> </property> <property> <name>yarn.nodemanager.auxservices.mapreduce.shuffle.class</name> <value>org.apache.hadoop.mapred.ShuffleHandler</value> </property> </configuration>
Create a SSH key. If you already have one, skip this step.
sudo ssh-keygen -t rsa
Copy the key to your authorized keys.
sudo cat /root/.ssh/id_rsa.pub | sudo tee -a /root/.ssh/authorized_keys
Log into the localhost. If no password prompt appears, you are ready to run the Hadoop daemons.
sudo ssh localhost
With all the configuration files properly edited, you are ready to start the daemons.
When you format the NameNode server, it formats the metadata related to data nodes. Thus, all the information on the data nodes is lost and the nodes can be reused for new data.
Format the NameNode server with the following command:
sudo hdfs namenode -format
Start the DFS in NameNode and DataNodes with the following command:
The console output should be similar to:
Starting namenodes on [localhost] The authenticity of host 'localhost (::1)' can't be established. ECDSA key fingerprint is SHA256:97e+7TnomsS9W7GjFPjzY75HGBp+f1y6sA+ZFcOPIPU. Are you sure you want to continue connecting (yes/no)?
Enter yes to continue.
Start the YARN daemons ResourceManager and NodeManager with the following command:
Ensure everything is running as expected with the following command:
The console output should be similar to:
22674 DataNode 26228 Jps 22533 NameNode 23046 ResourceManager 22854 SecondaryNameNode 23150 NodeManager
Create the input directory.
sudo hdfs dfs -mkdir -p /user/root/input
Copy a file from the local file system to the HDFS.
sudo hdfs dfs -copyFromLocal local-file /user/root/input
Run the wordcount example.
sudo hadoop jar /usr/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.8.0.jar wordcount input output
Read the output file “part-r-00000”. This file contains the number of times each word appears in the file.
sudo hdfs dfs -cat /user/root/output/part-r-00000
You have successfully installed and setup a single node Hadoop cluster. Additionally, you ran a simple wordcount example.
Your single node Hadoop cluster is up and running!