Hadoop Quickstart

The purpose of this document is to help users get a single-node Hadoop installation up and running very quickly so that users can get a flavour of the Hadoop Distributed File System (HDFS) and the Map-Reduce framework i.e. perform simple operations on HDFS, run example/simple jobs etc.

Supported Platforms

• Hadoop has been demonstrated on GNU/Linux clusters with 2000 nodes.
• Win32 is supported as a development platform. Distributed operation has not been well tested on Win32, so this is not a production platform.

Required Software

1. Java^TM 1.5.x, preferably from Sun, must be installed. Set JAVA_HOME to the root of your Java installation.
2. ssh must be installed and sshd must be running to use the Hadoop scripts that manage remote Hadoop daemons.

Additional requirements for Windows

1. Cygwin - Required for shell support in addition to the required software above.

Installing Software

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

On Windows, if you did not install the required software when you installed cygwin, start the cygwin installer and select the packages:

• openssh - the Net category

First, you need to get a Hadoop distribution: download a recent stable release and unpack it.

Once done, in the distribution edit the file conf/hadoop-env.sh to define at least JAVA_HOME.

Try the following command:
$ bin/hadoop
This will display the usage documentation for the hadoop script.

By default, Hadoop is configured to run things 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 conf/*.xml input
$ bin/hadoop jar hadoop-*-examples.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.

Configuration

Use the following conf/hadoop-site.xml:

Setup passphraseless ssh

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 dsa -P '' -f ~/.ssh/id_dsa
$ cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys

Execution

Format a new distributed-filesystem:
$ bin/hadoop namenode -format

Start The hadoop daemons:
$ bin/start-all.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 and the JobTracker, by default they are available at:

• NameNode - http://localhost:50070/
• JobTracker - http://localhost:50030/

Copy the input files into the distributed filesystem:
$ bin/hadoop dfs -put conf input

Run some of the examples provided:
$ bin/hadoop jar hadoop-*-examples.jar grep input output 'dfs[a-z.]+'

Examine the output files:

Copy the output files from the distributed filesystem to the local filesytem and examine them:
$ bin/hadoop dfs -get output output
$ cat output/*

or

View the output files on the distributed filesystem:
$ bin/hadoop dfs -cat output/*

When you're done, stop the daemons with:
$ bin/stop-all.sh

Information on setting up fully-distributed non-trivial clusters can be found here.