How To Install and Configure Hadoop on CentOS/RHEL 8

Hadoop is a free, open-source and Java-based software framework used for storage and processing of large datasets on clusters of machines. It uses HDFS to store its data and process these data using MapReduce. It is an ecosystem of Big Data tools that are primarily used for data mining and machine learning. It has four major components such as Hadoop Common, HDFS, YARN, and MapReduce.

In this guide, we will explain how to install Apache Hadoop on RHEL/CentOS 8.

Step 1 – Disable SELinux

Before starting, it is a good idea to disable the SELinux in your system.

To disable SELinux, open the /etc/selinux/config file:

nano /etc/selinux/config

Change the following line:

SELINUX=disabled

Save the file when you are finished. Next, restart your system to apply the SELinux changes.

Step 2 – Install Java

Hadoop is written in Java and supports only Java version 8. You can install OpenJDK 8 and ant using DNF command as shown below:

dnf install java-1.8.0-openjdk ant -y

Once installed, verify the installed version of Java with the following command:

java -version

You should get the following output:

openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-b09)
OpenJDK 64-Bit Server VM (build 25.232-b09, mixed mode)

Step 3 – Create a Hadoop User

It is a good idea to create a separate user to run Hadoop for security reasons.

Run the following command to create a new user with name hadoop:

useradd hadoop

Next, set the password for this user with the following command:

passwd hadoop

Provide and confirm the new password as shown below:

Changing password for user hadoop.
New password: 
Retype new password: 
passwd: all authentication tokens updated successfully.

Step 4 – Configure SSH Key-based Authentication

Next, you will need to configure passwordless SSH authentication for the local system.

First, change the user to hadoop with the following command:

su - hadoop

Next, run the following command to generate Public and Private Key Pairs:

ssh-keygen -t rsa

You will be asked to enter the filename. Just press Enter to complete the process:

Generating public/private rsa key pair.
Enter file in which to save the key (/home/hadoop/.ssh/id_rsa): 
Created directory '/home/hadoop/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/hadoop/.ssh/id_rsa.
Your public key has been saved in /home/hadoop/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:a/og+N3cNBssyE1ulKK95gys0POOC0dvj+Yh1dfZpf8 hadoop@centos8
The key's randomart image is:
+---[RSA 2048]----+
|                 |
|                 |
|              .  |
|     .   o o o   |
|  . . o S o o    |
| o = + O o   .   |
|o * O = B =   .  |
| + O.O.O + +   . |
|  +=*oB.+ o     E|
+----[SHA256]-----+

Next, append the generated public keys from id_rsa.pub to authorized_keys and set proper permission:

cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
chmod 640 ~/.ssh/authorized_keys

Next, verify the passwordless SSH authentication with the following command:

ssh localhost

You will be asked to authenticate hosts by adding RSA keys to known hosts. Type yes and hit Enter to authenticate the localhost:

The authenticity of host 'localhost (::1)' can't be established.
ECDSA key fingerprint is SHA256:0YR1kDGu44AKg43PHn2gEnUzSvRjBBPjAT3Bwrdr3mw.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.
Activate the web console with: systemctl enable --now cockpit.socket

Last login: Sat Feb  1 02:48:55 2020
[hadoop@centos8 ~]$ 

Step 5 – Install Hadoop

First, change the user to hadoop with the following command:

su - hadoop

Next, download the latest version of Hadoop using the wget command:

wget http://apachemirror.wuchna.com/hadoop/common/hadoop-3.2.1/hadoop-3.2.1.tar.gz

Once downloaded, extract the downloaded file:

tar -xvzf hadoop-3.2.1.tar.gz

Next, rename the extracted directory to hadoop:

mv hadoop-3.2.1 hadoop

Next, you will need to configure Hadoop and Java Environment Variables on your system.

Open the ~/.bashrc file in your favorite text editor:

nano ~/.bashrc

Append the following lines:

export JAVA_HOME=/usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.232.b09-2.el8_1.x86_64/
export HADOOP_HOME=/home/hadoop/hadoop
export HADOOP_INSTALL=$HADOOP_HOME
export HADOOP_MAPRED_HOME=$HADOOP_HOME
export HADOOP_COMMON_HOME=$HADOOP_HOME
export HADOOP_HDFS_HOME=$HADOOP_HOME
export HADOOP_YARN_HOME=$HADOOP_HOME
export HADOOP_COMMON_LIB_NATIVE_DIR=$HADOOP_HOME/lib/native
export PATH=$PATH:$HADOOP_HOME/sbin:$HADOOP_HOME/bin
export HADOOP_OPTS="-Djava.library.path=$HADOOP_HOME/lib/native"

Save and close the file. Then, activate the environment variables with the following command:

source ~/.bashrc

Next, open the Hadoop environment variable file:

nano $HADOOP_HOME/etc/hadoop/hadoop-env.sh

Update the JAVA_HOME variable as per your Java installation path:

export JAVA_HOME=/usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.232.b09-2.el8_1.x86_64/

Save and close the file when you are finished.

Step 6 – Configure Hadoop

First, you will need to create the namenode and datanode directories inside Hadoop home directory:

Run the following command to create both directories:

mkdir -p ~/hadoopdata/hdfs/namenode
mkdir -p ~/hadoopdata/hdfs/datanode

Next, edit the core-site.xml file and update with your system hostname:

nano $HADOOP_HOME/etc/hadoop/core-site.xml

Change the following name as per your system hostname:

Save and close the file. Then, edit the hdfs-site.xml file:

nano $HADOOP_HOME/etc/hadoop/hdfs-site.xml

Change the NameNode and DataNode directory path as shown below:

Save and close the file. Then, edit the mapred-site.xml file:

nano $HADOOP_HOME/etc/hadoop/mapred-site.xml

Make the following changes:

Save and close the file. Then, edit the yarn-site.xml file:

nano $HADOOP_HOME/etc/hadoop/yarn-site.xml

Make the following changes:

Save and close the file when you are finished.

Step 7 – Start Hadoop Cluster

Before starting the Hadoop cluster. You will need to format the Namenode as a hadoop user.

Run the following command to format the hadoop Namenode:

hdfs namenode -format

You should get the following output:

2020-02-05 03:10:40,380 INFO namenode.NNStorageRetentionManager: Going to retain 1 images with txid >= 0
2020-02-05 03:10:40,389 INFO namenode.FSImage: FSImageSaver clean checkpoint: txid=0 when meet shutdown.
2020-02-05 03:10:40,389 INFO namenode.NameNode: SHUTDOWN_MSG: 
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at hadoop.tecadmin.com/45.58.38.202
************************************************************/

After formating the Namenode, run the following command to start the hadoop cluster:

start-dfs.sh

Once the HDFS started successfully, you should get the following output:

Starting namenodes on [hadoop.tecadmin.com]
hadoop.tecadmin.com: Warning: Permanently added 'hadoop.tecadmin.com,fe80::200:2dff:fe3a:26ca%eth0' (ECDSA) to the list of known hosts.
Starting datanodes
Starting secondary namenodes [hadoop.tecadmin.com]

Next, start the YARN service as shown below:

start-yarn.sh

You should get the following output:

Starting resourcemanager
Starting nodemanagers

You can now check the status of all Hadoop services using the jps command:

jps

You should see all the running services in the following output:

7987 DataNode
9606 Jps
8183 SecondaryNameNode
8570 NodeManager
8445 ResourceManager
7870 NameNode

Step 8 – Configure Firewall

Hadoop is now started and listening on port 9870 and 8088. Next, you will need to allow these ports through the firewall.

Run the following command to allow Hadoop connections through the firewall:

firewall-cmd --permanent --add-port=9870/tcp
firewall-cmd --permanent --add-port=8088/tcp

Next, reload the firewalld service to apply the changes:

firewall-cmd --reload

Step 9 – Access Hadoop Namenode and Resource Manager

To access the Namenode, open your web browser and visit the URL http://your-server-ip:9870. You should see the following screen:

To access the Resource Manage, open your web browser and visit the URL http://your-server-ip:8088. You should see the following screen:

Step 10 – Verify the Hadoop Cluster

At this point, the Hadoop cluster is installed and configured. Next, we will create some directories in HDFS filesystem to test the Hadoop.

Let’s create some directory in the HDFS filesystem using the following command:

hdfs dfs -mkdir /test1
hdfs dfs -mkdir /test2

Next, run the following command to list the above directory:

hdfs dfs -ls /

You should get the following output:

Found 2 items
drwxr-xr-x   - hadoop supergroup          0 2020-02-05 03:25 /test1
drwxr-xr-x   - hadoop supergroup          0 2020-02-05 03:35 /test2

You can also verify the above directory in the Hadoop Namenode web interface.

Go to the Namenode web interface, click on the Utilities => Browse the file system. You should see your directories which you have created earlier in the following screen:

Step 11 – Stop Hadoop Cluster

You can also stop the Hadoop Namenode and Yarn service any time by running the stop-dfs.sh and stop-yarn.sh script as a Hadoop user.

To stop the Hadoop Namenode service, run the following command as a hadoop user:

stop-dfs.sh 

To stop the Hadoop Resource Manager service, run the following command:

stop-yarn.sh

Conclusion

In the above tutorial, you learned how to set up the Hadoop single node cluster on CentOS 8. I hope you have now enough knowledge to install the Hadoop in the production environment.