Every major industry is implementing Apache Hadoop as the standard framework for processing and storing big data. Hadoop is designed to be deployed across a network of hundreds or even thousands of dedicated servers. All these machines work together to deal with the massive volume and variety of incoming datasets.
Deploying Hadoop services on a single node is a great way to get yourself acquainted with basic Hadoop commands and concepts.
This easy-to-follow guide helps you install Hadoop on Ubuntu 18.04 or Ubuntu 20.04.
- Access to a terminal window/command line
- Sudo or root privileges on local /remote machines
Install OpenJDK on Ubuntu
The Hadoop framework is written in Java, and its services require a compatible Java Runtime Environment (JRE) and Java Development Kit (JDK). Use the following command to update your system before initiating a new installation:
sudo apt update
At the moment, Apache Hadoop 3.x fully supports Java 8. The OpenJDK 8 package in Ubuntu contains both the runtime environment and development kit.
Type the following command in your terminal to install OpenJDK 8:
sudo apt install openjdk-8-jdk -y
The OpenJDK or Oracle Java version can affect how elements of a Hadoop ecosystem interact. To install a specific Java version, check out our detailed guide on how to install Java on Ubuntu.
Once the installation process is complete, verify the current Java version:
java -version; javac -version
The output informs you which Java edition is in use.
Set Up a Non-Root User for Hadoop Environment
It is advisable to create a non-root user, specifically for the Hadoop environment. A distinct user improves security and helps you manage your cluster more efficiently. To ensure the smooth functioning of Hadoop services, the user should have the ability to establish a passwordless SSH connection with the localhost.
Install OpenSSH on Ubuntu
Install the OpenSSH server and client using the following command:
sudo apt install openssh-server openssh-client -y
In the example below, the output confirms that the latest version is already installed.
If you have installed OpenSSH for the first time, use this opportunity to implement these vital SSH security recommendations.
Create Hadoop User
adduser command to create a new Hadoop user:
sudo adduser hdoop
The username, in this example, is hdoop. You are free the use any username and password you see fit. Switch to the newly created user and enter the corresponding password:
su - hdoop
The user now needs to be able to SSH to the localhost without being prompted for a password.
Enable Passwordless SSH for Hadoop User
Generate an SSH key pair and define the location is is to be stored in:
ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa
The system proceeds to generate and save the SSH key pair.
cat command to store the public key as authorized_keys in the ssh directory:
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
Set the permissions for your user with the
chmod 0600 ~/.ssh/authorized_keys
The new user is now able to SSH without needing to enter a password every time. Verify everything is set up correctly by using the hdoop user to SSH to localhost:
After an initial prompt, the Hadoop user is now able to establish an SSH connection to the localhost seamlessly.
Download and Install Hadoop on Ubuntu
Visit the official Apache Hadoop project page, and select the version of Hadoop you want to implement.
The steps outlined in this tutorial use the Binary download for Hadoop Version 3.2.1.
Select your preferred option, and you are presented with a mirror link that allows you to download the Hadoop tar package.
Note: It is sound practice to verify Hadoop downloads originating from mirror sites. The instructions for using GPG or SHA-512 for verification are provided on the official download page.
Use the provided mirror link and download the Hadoop package with the
Once the download is complete, extract the files to initiate the Hadoop installation:
tar xzf hadoop-3.2.1.tar.gz
The Hadoop binary files are now located within the hadoop-3.2.1 directory.
Single Node Hadoop Deployment (Pseudo-Distributed Mode)
Hadoop excels when deployed in a fully distributed mode on a large cluster of networked servers. However, if you are new to Hadoop and want to explore basic commands or test applications, you can configure Hadoop on a single node.
This setup, also called pseudo-distributed mode, allows each Hadoop daemon to run as a single Java process. A Hadoop environment is configured by editing a set of configuration files:
Configure Hadoop Environment Variables (bashrc)
Edit the .bashrc shell configuration file using a text editor of your choice (we will be using nano):
sudo nano .bashrc
Define the Hadoop environment variables by adding the following content to the end of the file:
#Hadoop Related Options
Once you add the variables, save and exit the .bashrc file.
It is vital to apply the changes to the current running environment by using the following command:
Edit hadoop-env.sh File
When setting up a single node Hadoop cluster, you need to define which Java implementation is to be utilized. Use the previously created
$HADOOP_HOME variable to access the hadoop-env.sh file:
sudo nano $HADOOP_HOME/etc/hadoop/hadoop-env.sh
$JAVA_HOME variable (i.e., remove the
# sign) and add the full path to the OpenJDK installation on your system. If you have installed the same version as presented in the first part of this tutorial, add the following line:
The path needs to match the location of the Java installation on your system.
If you need help to locate the correct Java path, run the following command in your terminal window:
The resulting output provides the path to the Java binary directory.
Use the provided path to find the OpenJDK directory with the following command:
readlink -f /usr/bin/javac
The section of the path just before the /bin/javac directory needs to be assigned to the
Edit core-site.xml File
The core-site.xml file defines HDFS and Hadoop core properties.
To set up Hadoop in a pseudo-distributed mode, you need to specify the URL for your NameNode, and the temporary directory Hadoop uses for the map and reduce process.
Open the core-site.xml file in a text editor:
sudo nano $HADOOP_HOME/etc/hadoop/core-site.xml
Add the following configuration to override the default values for the temporary directory and add your HDFS URL to replace the default local file system setting:
This example uses values specific to the local system. You should use values that match your systems requirements. The data needs to be consistent throughout the configuration process.
Do not forget to create a Linux directory in the location you specified for your temporary data.
Edit hdfs-site.xml File
The properties in the hdfs-site.xml file govern the location for storing node metadata, fsimage file, and edit log file. Configure the file by defining the NameNode and DataNode storage directories.
Additionally, the default
dfs.replication value of
3 needs to be changed to
1 to match the single node setup.
Use the following command to open the hdfs-site.xml file for editing:
sudo nano $HADOOP_HOME/etc/hadoop/hdfs-site.xml
Add the following configuration to the file and, if needed, adjust the NameNode and DataNode directories to your custom locations:
If necessary, create the specific directories you defined for the
Edit mapred-site.xml File
Use the following command to access the mapred-site.xml file and define MapReduce values:
sudo nano $HADOOP_HOME/etc/hadoop/mapred-site.xml
Add the following configuration to change the default MapReduce framework name value to
Edit yarn-site.xml File
The yarn-site.xml file is used to define settings relevant to YARN. It contains configurations for the Node Manager, Resource Manager, Containers, and Application Master.
Open the yarn-site.xml file in a text editor:
sudo nano $HADOOP_HOME/etc/hadoop/yarn-site.xml
Append the following configuration to the file:
Format HDFS NameNode
It is important to format the NameNode before starting Hadoop services for the first time:
hdfs namenode -format
The shutdown notification signifies the end of the NameNode format process.
Start Hadoop Cluster
Navigate to the hadoop-3.2.1/sbin directory and execute the following commands to start the NameNode and DataNode:
The system takes a few moments to initiate the necessary nodes.
Once the namenode, datanodes, and secondary namenode are up and running, start the YARN resource and nodemanagers by typing:
As with the previous command, the output informs you that the processes are starting.
Type this simple command to check if all the daemons are active and running as Java processes:
If everything is working as intended, the resulting list of running Java processes contains all the HDFS and YARN daemons.
Access Hadoop UI from Browser
Use your preferred browser and navigate to your localhost URL or IP. The default port number 9870 gives you access to the Hadoop NameNode UI:
The NameNode user interface provides a comprehensive overview of the entire cluster.
The default port 9864 is used to access individual DataNodes directly from your browser:
The YARN Resource Manager is accessible on port 8088:
The Resource Manager is an invaluable tool that allows you to monitor all running processes in your Hadoop cluster.
You have successfully installed Hadoop on Ubuntu and deployed it in a pseudo-distributed mode. A single node Hadoop deployment is an excellent starting point to explore basic HDFS commands and acquire the experience you need to design a fully distributed Hadoop cluster.