Notes on Hadoop

http://wiki.apache.org/hadoop/GettingStartedWithHadoop
Data Path Settings - Figure out where your data goes. This includes settings for where the namenode stores the namespace checkpoint and the edits log, where the datanodes store filesystem blocks, storage locations for Map/Reduce intermediate output and temporary storage for the HDFS client. The default values for these paths point to various locations in /tmp. While this might be ok for a single node installation, for larger clusters storing data in /tmp is not an option. These settings must also be in hadoop-site.xml. It is important for these settings to be present in hadoop-site.xml because they can otherwise be overridden by client configuration settings in Map/Reduce jobs. 
dfs.name.dir
dfs.data.dir
dfs.client.buffer.dir
mapred.local.dir
An example of a hadoop-site.xml file:
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
<property>
  <name>hadoop.tmp.dir</name>
  <value>/tmp/hadoop-${user.name}</value>
</property>
<property>
  <name>fs.default.name</name>
  <value>hdfs://localhost:54310</value>
</property>
<property>
  <name>mapred.job.tracker</name>
  <value>hdfs://localhost:54311</value>
</property>
<property> 
  <name>dfs.replication</name>
  <value>8</value>
</property>
<property>
  <name>mapred.child.java.opts</name>
  <value>-Xmx512m</value>
</property>
</configuration>

http://hadoop.apache.org/docs/r2.3.0/hadoop-project-dist/hadoop-common/SingleNodeSetup.html
sudo apt-get install ssh
sudo apt-get install rsync

Unpack the downloaded Hadoop distribution. In the distribution, edit the file conf/hadoop-env.sh to define at least JAVA_HOME to be the root of your Java installation.
Try the following command:
bin/hadoop

Standalone Operation
mkdir input
cp conf/*.xml input
bin/hadoop jar hadoop-*-examples.jar grep input output 'dfs[a-z.]+'
cat output/*