56f1136b_Hadoop_Troubleshooting__Possible_Problem
[Symptom] When you try the grep example in the QuickStart, you get an error like the following: org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory /user/ross/output already exists [Possible Solution] Remove the output directory before rerunning the example: bin/hadoop dfs -rmr output Alternatively you can change the output directory of the grep example, something like this: bin/hadoop jar hadoop-*-examples.jar \ grep input output2 'dfs[a-z.]+' [Possible Problem] 
You might have already run the example once, creating an output directory. Hadoop doesn't like to overwrite files.
Hadoop Troubleshooting
Possible Problem