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Operating with Hadoop ?

+1 vote
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I want to know the installation and configuration of Apache Hadoop and Programming Paradigm for working on it..

posted Aug 11, 2013 by Sudhakar Singh

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1 Answer

+1 vote

These are two question let me answer the first one configuration of Apache Hadoop (source http://hadoop.apache.org/docs/stable/single_node_setup.html), please comment on second part i.e. Programming Paradigm and be specific what is your question so that it can be answered.

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
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:

Local (Standalone) Mode
Pseudo-Distributed Mode
Fully-Distributed Mode

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

Pseudo-Distributed Operation
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/core-site.xml:

<configuration>
     <property>
         <name>fs.default.name</name>
         <value>hdfs://localhost:9000</value>
     </property>
</configuration>

conf/hdfs-site.xml:

<configuration>
     <property>
         <name>dfs.replication</name>
         <value>1</value>
     </property>
</configuration>

conf/mapred-site.xml:

<configuration>
     <property>
         <name>mapred.job.tracker</name>
         <value>localhost:9001</value>
     </property>
</configuration>

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 fs -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 fs -get output output
$ cat output/*

or

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

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

answer Aug 12, 2013 by Salil Agrawal
To be specific with Programming Paradigm I mean how to do programming on Hadoop, which language is used ? Is there any particular reference for beginners ?
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I have a working version of java 7 installed. I can execute java programs in the workstation. When I start hdfs, the statup process aborts with a message JAVA_HOME not set.

OS : Ubuntu 13.04 raring ringtail
Hadoop version : 2.1.1-beta
Java version:java-7-openjdk-amd64


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