Links:

Hadoop Website

Hadoop at Yahoo!

Setup

TODO

Command line basics

ENVIRONMENT VARIABLES

in ~/.bash_profile

# User specific environment and startup programs
JAVA_HOME=/opt/java
HADOOP_HOME=/opt/hadoop
HIVE_HOME=/opt/hive

PATH=$JAVA_HOME/bin:$HADOOP_HOME/bin:$HIVE_HOME/bin:$PATH:$HOME/bin

export PATH JAVA_HOME HADOOP_HOME

HDFS – Walk around

hadoop fs -ls /
hadoop fs -du -h /data/
hadoop fs -dus /user/_myname_/
hadoop fs -tail /user/_myname_/my-test-file.txt

Submit Map/Reduce Job(jar)

Job Tracker

TODO

Streaming

Streaming(script)

Usage:

 hadoop jar $STREAMING_JAR -mapper "$MAPPER" -file $MAPPER_FILE -reducer "$REDUCER" -file $REDUCER_FILE -input $RAW -output $SUMMARY -numReduceTasks 1

$STREAMING_JAR, $MAPPER_FILE, $REDUCER_FILE: files in local path.

$MAPPER，$REDUCER: commands run by hadoop.

$RAW, $SUMMARY: files in HDFS.

Streaming examples

EXAMPLES: streaming/wc-demo.sh