brew install hadoop
$ hdfs namenode -format # format file system
$ start-dfs.sh
$ start-yarn.sh
$ hdfs dfs -mkdir input
$ hdfs dfs -rm -r input
$ # transfer files to input for testing
$ hdfs dfs -put /usr/local/Cellar/hadoop/2.7.2/libexec/etc/hadoop/ input
$ hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.2.jar wordcount input output