Hadoop Beginner's Guide

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Time for action – downloading Hadoop

Carry out the following steps to download Hadoop:

Go to the Hadoop download page at http://hadoop.apache.org/common/releases.html and retrieve the latest stable version of the 1.0.x branch; at the time of this writing, it was 1.0.4.
You'll be asked to select a local mirror; after that you need to download the file with a name such as hadoop-1.0.4-bin.tar.gz.
Copy this file to the directory where you want Hadoop to be installed (for example, /usr/local), using the following command:
```
$ cp Hadoop-1.0.4.bin.tar.gz /usr/local
```
Decompress the file by using the following command:
```
$ tar –xf hadoop-1.0.4-bin.tar.gz
```
Add a convenient symlink to the Hadoop installation directory.
```
$ ln -s /usr/local/hadoop-1.0.4 /opt/hadoop
```
Now you need to add the Hadoop binary directory to your path and set the HADOOP_HOME environment variable, just as we did earlier with Java.
```
$ export HADOOP_HOME=/usr/local/Hadoop
$ export PATH=$HADOOP_HOME/bin:$PATH
```
Go into the conf directory within the Hadoop installation and edit the Hadoop-env.sh file. Search for JAVA_HOME and uncomment the line, modifying the location to point to your JDK installation, as mentioned earlier.

What just happened?

These steps ensure that Hadoop is installed and available from the command line. By setting the path and configuration variables, we can use the Hadoop command-line tool. The modification to the Hadoop configuration file is the only required change to the setup needed to integrate with your host settings.

As mentioned earlier, you should put the export commands in your shell startup file or a standalone-configuration script that you specify at the start of the session.

Don't worry about some of the details here; we'll cover Hadoop setup and use later.