MapReduce on Hadoop said “output file already exists”

10P:/$ hadoop jar /usr/local/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.6.0 .jar wordcount /user/test/tester /user/output
15/08/05 00:16:04 INFO Configuration.deprecation: session.id is deprecated. Instead, use dfs.metrics.session-id
15/08/05 00:16:04 INFO jvm.JvmMetrics: Initializing JVM Metrics with processName=JobTracker, sessionId=
org.apache.hadoop.mapred.FileAlreadyExistsException: **Output directory hdfs://localhost :54310/user/output already exists**
 at org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:146)
 at org.apache.hadoop.mapreduce. JobSubmitter.checkSpecs(JobSubmitter.java:562)
 at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:432)
 at org.apache.hadoop.mapreduce.Job$10.run (Job.java:1296)
 at org.apac he.hadoop.mapreduce.Job$10.run(Job.java:1293)
 at java.security.AccessController.doPrivileged(Native Method)
 at javax.security.auth.Subject.doAs(Subject. java:415)
 at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
 at org.apache.hadoop.mapreduce.Job.submit(Job.java:1293) 
 at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1314)
 at org.apache.hadoop.examples.WordCount.main(WordCount.java:87)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
 at java.lang.reflect.Method.invoke(Method.java:606)
 at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:71)
 at org.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:144)
 at org.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:74)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java :57)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:606)
 at org. apache.hadoop.util.RunJar.run(RunJar.java:221)
 at org.apache.hadoop.util.RunJar.main(RunJar.java:136)

hadoop fs -rm -r /user/output

I ran a wordcount example using Mapreduce for the first time, and it worked. Then, I stopped the cluster, started it temporarily, and followed the same steps.

This error is displayed:

10P:/$ hadoop jar /usr/local/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.6. 0.jar wordcount /user/test/tester /user/output
15/08/05 00:16:04 INFO Configuration.deprecation: session.id is deprecated. Instead, use dfs.metrics.session-id
15/08/05 00:16:04 INFO jvm.JvmMetrics: Initializing JVM Metrics with processName=JobTracker, sessionId= 
org.apache.hadoop.mapred.FileAlreadyExistsException: **Output directory hdfs://localhost:54310/user/output already exists**
 at org.apache.hadoop.mapreduce.lib.output. FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:146)
 at org.apache.hadoop.mapreduce.JobSubmitter.checkSpecs(JobSubmitter.java:562)
 at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal( JobSubmitter.java:432)
 at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1296)
 at org.apache.hadoop.mapreduce.Job$10.run(Job. java:1293)
 at java.security.AccessController.doPrivileged(Native Method)
 at javax.security.auth.Subject.doAs(Subject.java:415)
 at org.apache. hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
 at org.apache.hadoop.mapreduce.Job.submit(Job.java:1293)
 at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1314)
 at org.apache. hadoop.examples.WordCount.main(WordCount.java:87)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)< br /> at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:606)
 at org.apache.hadoop. util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:71)
 at org.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:144)
 at org.apache.hadoop.examples. ExampleDriver.main(ExampleDriver.java:74)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
 at sun.reflect.DelegatingMethodAccessorImpl.invo ke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:606)
 at org.apache.hadoop.util.RunJar.run(RunJar.java: 221)
 at org.apache.hadoop.util.RunJar.main(RunJar.java:136)

HDFS: //Local host: 54310 /User/Output

Delete the output directory before running the job.

Execute the following command:

hadoop fs -rm -r /user/output

Before running the job.