http://stackoverflow.com/questions/8464048/out-of-memory-error-in-hadoop

I am getting the following Exception

java.lang.OutOfMemoryError: Java heap space
Please suggest a solution so that i can try out the example. The entire Exception is listed below. I am new to Hadoop I might have done something dumb . Any suggestion will be highly appreciated.

anuj@anuj-VPCEA13EN:~/hadoop$ bin/hadoop jar hadoop-examples-*.jar grep input output 'dfs[a-z.]+'
11/12/11 17:38:22 INFO util.NativeCodeLoader: Loaded the native-hadoop library
11/12/11 17:38:22 INFO mapred.FileInputFormat: Total input paths to process : 7
11/12/11 17:38:22 INFO mapred.JobClient: Running job: job_local_0001
11/12/11 17:38:22 INFO util.ProcessTree: setsid exited with exit code 0
11/12/11 17:38:22 INFO mapred.Task: Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@e49dcd
11/12/11 17:38:22 INFO mapred.MapTask: numReduceTasks: 1
11/12/11 17:38:22 INFO mapred.MapTask: io.sort.mb = 100
11/12/11 17:38:22 WARN mapred.LocalJobRunner: job_local_0001
java.lang.OutOfMemoryError: Java heap space
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.(MapTask.java:949)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:428)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:212)
11/12/11 17:38:23 INFO mapred.JobClient: map 0% reduce 0%
11/12/11 17:38:23 INFO mapred.JobClient: Job complete: job_local_0001
11/12/11 17:38:23 INFO mapred.JobClient: Counters: 0
11/12/11 17:38:23 INFO mapred.JobClient: Job Failed: NA
java.io.IOException: Job failed!
at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1257)
at org.apache.hadoop.examples.Grep.run(Grep.java:69)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
at org.apache.hadoop.examples.Grep.main(Grep.java:93)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:68)
at org.apache.hadoop.util.ProgramDriver.driver(ProgramDriver.java:139)
at org.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:64)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.util.RunJar.main(RunJar.java:156)

You can assign more memory by editing the conf/mapred-site.xml file and adding the property:

  <property>
    <name>mapred.child.java.opts</name>
    <value>-Xmx1024m</value>
  </property>

This will start the hadoop JVMs with more heap space.