Prerequisites
GNU/Linux is supported as a development and production platform. Hadoop has been demonstrated on GNU/Linux clusters with 2000 nodes.
Windows is also a supported platform but the followings steps are for Linux only. To set up Hadoop on Windows, see wiki page.
Required software for Linux include:
Java™ must be installed. Recommended Java versions are described at HadoopJavaVersions.
ssh must be installed and sshd must be running to use the Hadoop scripts that manage remote Hadoop daemons.
If your cluster doesn’t have the requisite software you will need to install it.
For example on Ubuntu Linux:
$ sudo apt-get install ssh
$ sudo apt-get install rsync
To get a Hadoop distribution, download a recent stable release from one of the Apache Download Mirrors.
Prepare to Start the Hadoop Cluster
Unpack the downloaded Hadoop distribution. In the distribution, edit the file etc/hadoop/hadoop-env.sh to define some parameters as follows:
# set to the root of your Java installation
export JAVA_HOME=/usr/java/latest
Try the following command:
$ bin/hadoop
This will display the usage documentation for the hadoop script.
Now you are ready to start your Hadoop cluster in one of the three supported modes:
By default, Hadoop is configured to run in a non-distributed mode, as a single Java process. This is useful for debugging.
The following example copies the unpacked conf directory to use as input and then finds and displays every match of the given regular expression. Output is written to the given output directory.
$ mkdir input
$ cp etc/hadoop/*.xml input
$ bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.9.2.jar grep input output 'dfs[a-z.]+'
$ cat output/*
Hadoop can also be run on a single-node in a pseudo-distributed mode where each Hadoop daemon runs in a separate Java process.
Use the following:
etc/hadoop/core-site.xml:
<configuration>
<property>
<name>fs.defaultFS</name>
<value>hdfs://localhost:9000</value>
</property>
</configuration>
etc/hadoop/hdfs-site.xml:
<configuration>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
</configuration>
Now check that you can ssh to the localhost without a passphrase:
$ ssh localhost
If you cannot ssh to localhost without a passphrase, execute the following commands:
$ ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa
$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
$ chmod 0600 ~/.ssh/authorized_keys
The following instructions are to run a MapReduce job locally. If you want to execute a job on YARN, see YARN on Single Node.
Format the filesystem:
$ bin/hdfs namenode -format
Start NameNode daemon and DataNode daemon:
$ sbin/start-dfs.sh
The hadoop daemon log output is written to the $HADOOP_LOG_DIR directory (defaults to $HADOOP_HOME/logs).
Browse the web interface for the NameNode; by default it is available at:
NameNode - http://localhost:50070/
Make the HDFS directories required to execute MapReduce jobs:
$ bin/hdfs dfs -mkdir /user
$ bin/hdfs dfs -mkdir /user/<username>
Copy the input files into the distributed filesystem:
$ bin/hdfs dfs -put etc/hadoop input
Run some of the examples provided:
