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https://issues.apache.org/jira/browse/MAPREDUCE-4857?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13619683#comment-13619683
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Fengdong Yu commented on MAPREDUCE-4857:
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bq. But, can you tell me how will i build this code.

under your $HADOOP_HOME/:

mvn -Dmaven.test.skip.exec=true package
                
> Fix 126 error during map/reduce phase
> -------------------------------------
>
>                 Key: MAPREDUCE-4857
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4857
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 1.0.4
>            Reporter: Fengdong Yu
>             Fix For: 1.0.4
>
>         Attachments: MAPREDUCE-4857.patch
>
>
> There is rare happenings during map or reduce phase, but mostly in map phase, 
> the Exception messages: 
> java.lang.Throwable: Child Error
>       at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:271)
> Caused by: java.io.IOException: Task process exit with nonzero status of 126.
>       at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:258)
> and error logs are cleaned, so It's very hard to debug.
> but I compared DefaultTaskController.java with 0.22, they use "bash command" 
> to start the job scritp, but 1.0.4 use "bash, "-c", command".
> I removed "-c", everything is ok, 126 error code never happen again.
> I read man document of bash, it indicates when fork a new thread with write 
> command, another thread with "bash -c" also has a writable fd. so I think it 
> could return 126 status occasionally.
> So, there is only one line fix for this issue.

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