Multi Node Cluster in Hadoop 2.x

Here, we are taking two machines – master and slave. On both the machines, a datanode will be running.

Let us start with the setup of Multi Node Cluster in Hadoop.

PREREQUISITES:

• Cent OS 6.5
• Hadoop-2.7.3
• JAVA 8
• SSH

We have two machines (master and slave) with IP:

Master IP: 192.168.56.102

Slave IP: 192.168.56.103

 1.Check the IP address of all machines.

ip addr show (you can use the ifconfig command as well)

2.Disable the firewall restrictions.

service iptables stop

sudo chkconfig iptables off

3.Open hosts file to add master and data node with their respective IP addresses.

sudo nano /etc/hosts

Same properties will be displayed in the master and slave hosts files.

4.Restart the sshd service.

service sshd restart

5.Create the SSH Key in the master node. (Press enter button when it asks you to enter a filename to save the key).

ssh-keygen -t rsa -P “”

6.Copy the generated ssh key to master node’s authorized keys.

cat $HOME/.ssh/id_rsa.pub >> $HOME/.ssh/authorized_keys

7.Copy the master node’s ssh key to slave’s authorized keys.

ssh-copy-id -i $HOME/.ssh/id_rsa.pub hadoop@slave

8. Click here to download the Java 8 Package. Save this file in your home directory.

9. Extract the Java Tar File on all nodes.

tar -xvf jdk-8u101-linux-i586.tar.gz

10: Download the Hadoop 2.7.3 Package on all nodes.

wget https://archive.apache.org/dist/hadoop/core/hadoop-2.7.3/hadoop-2.7.3.tar.gz

11: Extract the Hadoop tar File on all nodes.

tar -xvf hadoop-2.7.3.tar.gz

12: Add the Hadoop and Java paths in the bash file (.bashrc) on all nodes.

Open. bashrc file. Now, add Hadoop and Java Path as shown below:

sudo gedit .bashrc

Then, save the bash file and close it.

For applying all these changes to the current Terminal, execute the source command.

source .bashrc

To make sure that Java and Hadoop have been properly installed on your system and can be accessed through the Terminal. Execute the java -version and hadoop version commands.

Command: java -version

Command: hadoop version

Now edit the configuration files in hadoop-2.7.3/etc/hadoop directory.

 13: Create masters file and edit as follows in both master and slave machines as below:

sudo gedit masters

 14: Edit slaves file in master machine as follows:

sudo gedit /home/hadoop/hadoop-2.7.3/etc/hadoop/slaves

15: Edit slaves file in slave machine as follows:

sudo gedit /home/hadoop/hadoop-2.7.3/etc/hadoop/slaves

16. Edit core-site.xml on both master and slave machines as follows:

Command: sudo gedit /home/hadoop/hadoop-2.7.3/etc/hadoop/core-site.xml
<?xml version=”1.0″ encoding=”UTF-8″?>
<?xml-stylesheet type=”text/xsl” href=”configuration.xsl”?>
<configuration>
<property>
<name>fs.default.name</name>
<value>hdfs://master:9000</value>
</property>
</configuration>

17. Edit hdfs-site.xml on master as follows:

Command: sudo gedit /home/hadoop/hadoop-2.7.3/etc/hadoop/hdfs-site.xml
<?xml version=”1.0″ encoding=”UTF-8″?>
<?xml-stylesheet type=”text/xsl” href=”configuration.xsl”?>
<configuration>
<property>
<name>dfs.replication</name>
<value>2</value>
</property>
<property>
<name>dfs.permissions</name>
<value>false</value>
</property>
<property>
<name>dfs.namenode.name.dir</name>
<value>/home/hadoop/hadoop-2.7.3/namenode</value>
</property>
<property>
<name>dfs.datanode.data.dir</name>
<value>/home/hadoop/hadoop-2.7.3/datanode</value>
</property>
</configuration>

18. Edit hdfs-site.xml on slave machine as follows:

Command: sudo gedit /home/hadoop/hadoop-2.7.3/etc/hadoop/hdfs-site.xml

<?xml version=”1.0″ encoding=”UTF-8″?>
<?xml-stylesheet type=”text/xsl” href=”configuration.xsl”?>
<configuration>
<property>
<name>dfs.replication</name>
<value>2</value>
</property>
<property>
<name>dfs.permissions</name>
<value>false</value>
</property>
<property>
<name>dfs.datanode.data.dir</name>
<value>/home/hadoop/hadoop-2.7.3/datanode</value>
</property>
</configuration>

19. Copy mapred-site from the template in configuration folder and the edit mapred-site.xml on both master and slave machines 

 

Command: cp mapred-site.xml.template mapred-site.xml

Command: sudo gedit /home/hadoop/hadoop-2.7.3/etc/hadoop/mapred-site.xml

<?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>

20. Edit yarn-site.xml on both master and slave machines as follows:

Command: sudo gedit /home/hadoop/hadoop-2.7.3/etc/hadoop/yarn-site.xml
<?xml version=”1.0″ encoding=”UTF-8″?>
<?xml-stylesheet type=”text/xsl” href=”configuration.xsl”?>
<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>

 

 

21. Format the namenode (Only on master machine).

hadoop namenode -format

22. Start all daemons (Only on master machine).

./sbin/start-all.sh

23. Check all the daemons running on both master and slave machines.

jps

At last, open the browser and go to master:50070/dfshealth.html on your master machine, this will give you the NameNode interface. Scroll down and see for the number of live nodes, if its 2, you have successfully setup a multi node Hadoop cluster. In case, it’s not 2, you might have missed out any of the steps which I have mentioned above. But no need to worry, you can go back and verify all the configurations again to find the issues and then correct them.