Running a wordcount example provided by http://developer.yahoo.com/hadoop/tutorial/module3.html#running I am running hadoop on a VM

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Asked: June 7, 20262026-06-07T20:02:11+00:00 2026-06-07T20:02:11+00:00

Running a wordcount example provided by http://developer.yahoo.com/hadoop/tutorial/module3.html#running I am running hadoop on a VM

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Running a wordcount example provided by http://developer.yahoo.com/hadoop/tutorial/module3.html#running
I am running hadoop on a VM provided by yahoo and connecting to the VM via ssh client.

I am getting these errors:

12/07/13 00:10:03 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
12/07/13 00:10:03 INFO mapred.FileInputFormat: Total input paths to process : 2
12/07/13 00:10:03 INFO mapred.FileInputFormat: Total input paths to process : 2
12/07/13 00:10:04 INFO mapred.JobClient: Running job: job_201207121015_0021
12/07/13 00:10:05 INFO mapred.JobClient:  map 0% reduce 0%
12/07/13 00:10:10 INFO mapred.JobClient: Task Id : attempt_201207121015_0021_m_000000_0, Status : FAILED
java.lang.UnsupportedClassVersionError: WordCountReducer : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:628)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:646)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:672)
    at org.apache.hadoop.mapred.JobConf.getCombinerClass(JobConf.java:780)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:403)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:193)
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2209)

12/07/13 00:10:10 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:10 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:10 INFO mapred.JobClient: Task Id : attempt_201207121015_0021_m_000001_0, Status : FAILED
java.lang.UnsupportedClassVersionError: WordCountReducer : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:628)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:646)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:672)
    at org.apache.hadoop.mapred.JobConf.getCombinerClass(JobConf.java:780)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:403)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:193)
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2209)

12/07/13 00:10:10 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:10 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:14 INFO mapred.JobClient: Task Id : attempt_201207121015_0021_m_000000_1, Status : FAILED
java.lang.UnsupportedClassVersionError: WordCountReducer : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:628)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:646)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:672)
    at org.apache.hadoop.mapred.JobConf.getCombinerClass(JobConf.java:780)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:403)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:193)
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2209)

12/07/13 00:10:14 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:14 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:15 INFO mapred.JobClient: Task Id : attempt_201207121015_0021_m_000001_1, Status : FAILED
java.lang.UnsupportedClassVersionError: WordCountReducer : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:628)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:646)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:672)
    at org.apache.hadoop.mapred.JobConf.getCombinerClass(JobConf.java:780)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:403)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:193)
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2209)

12/07/13 00:10:15 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:15 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:19 INFO mapred.JobClient: Task Id : attempt_201207121015_0021_m_000000_2, Status : FAILED
java.lang.UnsupportedClassVersionError: WordCountReducer : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:628)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:646)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:672)
    at org.apache.hadoop.mapred.JobConf.getCombinerClass(JobConf.java:780)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:403)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:193)
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2209)

12/07/13 00:10:19 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:19 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:19 INFO mapred.JobClient: Task Id : attempt_201207121015_0021_m_000001_2, Status : FAILED
java.lang.UnsupportedClassVersionError: WordCountReducer : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:628)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:646)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:672)
    at org.apache.hadoop.mapred.JobConf.getCombinerClass(JobConf.java:780)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:403)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:193)
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2209)

12/07/13 00:10:19 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
12/07/13 00:10:19 WARN mapred.JobClient: Error reading task outputhadoop-desk.localdomain
java.io.IOException: Job failed!
    at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1113)
    at WordCount.main(WordCount.java:33)

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1 Answer

Editorial Team · Answer 1 · 2026-06-07T20:02:13+00:00

Editorial Team

2026-06-07T20:02:13+00:00Added an answer on June 7, 2026 at 8:02 pm

You are compiling your code with Java7 whereas Hadoop is running on Java6. You could either let Hadoop run on Java7 or compile your code for Java6.

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