Installing Apache Hadoop on a Single Node

There are three modes where you can install Hadoop.

1. Standalone - Everything run on one JVM under one single machine.
2. Pseudo Distributed - Each run on it's own JVM under one machine. 
3. Fully Distributed -  Each Service run on it's on machine.

I am using the following Ubuntu, JDK and Hadoop versions:
Hadoop version: hadoop-1.2.1
JDK: openjdk-7-jdk
Ubuntu: Server 14.04 LTS

Configuration and Installation Steps for Pseudo Distributed mode

Generate the public/private RSA key, without a password and save the key file with the default name "id_rsa.pub".
ssh-keygen

Add the generated key to authorized key list
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
For the Fully Distributed mode this key file needs to be send to each node through the "ssh-copy" to avoid password prompts.

Try SSH connect, it shouldn't ask for password
ssh localhost

Install Open JDK
sudo apt-get install openjdk-7-jdk

Check the java version after the installation is completed
java -version

Download the Hadoop
wget http://apache.mirrors.pair.com/hadoop/common/hadoop-1.2.1/hadoop-1.2.1-bin.tar.gz

Unpack the downloaded file
tar -zxvf hadoop-1.2.1-bin.tar.gz

Copy the unpacked files to directory " /usr/local/hadoop".
sudo cp -r hadoop-1.2.1 /usr/local/hadoop

Change the owner to current user
sudo chown mahesh /usr/local/hadoop

Add Hadoop bin directory path to the bashrc file, so you can run Hadoop any directory. 
sudo vim $HOME/.bashrc

Go to the bottom of the file and add the following using a editor such as VIM.
export HADOOP_PREFIX=/usr/local/hadoop
export PATH=$PATH:$HADOOP_PREFIX/bin

Reload the script
exec bash

Check the whether the new path exists in the path variable
$PATH

Change JDK home and enable IP v4, Open following file (I have used the vim editor).
sudo vim /usr/local/hadoop/conf/hadoop-env.sh
Change highlighted lines

# Set Hadoop-specific environment variables here.

# The only required environment variable is JAVA_HOME.  All others are
# optional.  When running a distributed configuration it is best to
# set JAVA_HOME in this file, so that it is correctly defined on
# remote nodes.

# The java implementation to use.  Required.
export JAVA_HOME=/usr/lib/jvm/java-1.7.0-openjdk-amd64
# Extra Java CLASSPATH elements.  Optional.
# export HADOOP_CLASSPATH=

# The maximum amount of heap to use, in MB. Default is 1000.
# export HADOOP_HEAPSIZE=2000

# Extra Java runtime options.  Empty by default.
export HADOOP_OPTS=-Djava.net.preferIPv4Stack=true

# Command specific options appended to HADOOP_OPTS when specified
export HADOOP_NAMENODE_OPTS="-Dcom.sun.management.jmxremote $HADOOP_NAMENODE_OPTS"
export HADOOP_SECONDARYNAMENODE_OPTS="-Dcom.sun.management.jmxremote $HADOOP_SECONDARYNAMENODE_OPTS"


Configure the name node by editing following file.
sudo vim /usr/local/hadoop/conf/core-site.xml

Add the highlighted section
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

<configuration>
<property>
  <name>fs.default.name</name>
  <value>hdfs://mahesh-hd:10001</value>
</property>
<property>
  <name>hadoop.tmp.dir</name>
  <value>/usr/local/hadoop/tmp</value>
</property>
</configuration>

Create the temp directory
sudo mkdir /usr/local/hadoop/tmp

Change the owner to current user
sudo chown mahesh /usr/local/hadoop/tmp

Configure the MapReduce site
sudo vim /usr/local/hadoop/conf/mapred-site.xml

Add the highlighted section:
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

<configuration>
<property>
  <name>mapred.job.tracker</name>
  <value>hdfs://mahesh-hd:10002</value>
</property>
</configuration>

Format the name node
hadoop namenode -format

Following successful message should appear

Start all services using:
start-all.sh

Check whether all everything is running using "jps" command

Install Hadoop on Oracle JDK

Download and install Oracle JDK
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer

Change the hadoop-env.sh file java home directory according to the Oracle JDK path.