title: Hadoop error stalling job reduce process
body: <p>I have been running a Hadoop job(word count example) a few times on my two-node cluster setup, and it´s been working fine up until now. I keep getting a RuntimeException which stalls the reduce process at 19%:</p>
  
  <pre><code>    2013-04-13 18:45:22,191 INFO org.apache.hadoop.mapred.Task: Task:attempt_201304131843_0001_m_000000_0 is done. And is in the process of commiting
      2013-04-13 18:45:22,299 INFO org.apache.hadoop.mapred.Task: Task 'attempt_201304131843_0001_m_000000_0' done.
      2013-04-13 18:45:22,318 INFO org.apache.hadoop.mapred.TaskLogsTruncater: Initializing logs' truncater with mapRetainSize=-1 and reduceRetainSize=-1
      2013-04-13 18:45:23,181 WARN org.apache.hadoop.mapred.Child: Error running child
      java.lang.RuntimeException: Error while running command to get file permissions : org.apache.hadoop.util.Shell$ExitCodeException: 
      at org.apache.hadoop.util.Shell.runCommand(Shell.java:255)
  at org.apache.hadoop.util.Shell.run(Shell.java:182)
  at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:375)
  at org.apache.hadoop.util.Shell.execCommand(Shell.java:461)
  at org.apache.hadoop.util.Shell.execCommand(Shell.java:444)
  at org.apache.hadoop.fs.FileUtil.execCommand(FileUtil.java:710)
  at org.apache.hadoop.fs.RawLocalFileSystem$RawLocalFileStatus.loadPermissionInfo(RawLocalFileSystem.java:443)
  at org.apache.hadoop.fs.RawLocalFileSystem$RawLocalFileStatus.getOwner(RawLocalFileSystem.java:426)
  at org.apache.hadoop.mapred.TaskLog.obtainLogDirOwner(TaskLog.java:267)
  at org.apache.hadoop.mapred.TaskLogsTruncater.truncateLogs(TaskLogsTruncater.java:124)
  at org.apache.hadoop.mapred.Child$4.run(Child.java:260)
  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:1149)
  at org.apache.hadoop.mapred.Child.main(Child.java:249)
  
      at org.apache.hadoop.fs.RawLocalFileSystem$RawLocalFileStatus.loadPermissionInfo(RawLocalFileSystem.java:468)
  at org.apache.hadoop.fs.RawLocalFileSystem$RawLocalFileStatus.getOwner(RawLocalFileSystem.java:426)
  at org.apache.hadoop.mapred.TaskLog.obtainLogDirOwner(TaskLog.java:267)
  at org.apache.hadoop.mapred.TaskLogsTruncater.truncateLogs(TaskLogsTruncater.java:124)
  at org.apache.hadoop.mapred.Child$4.run(Child.java:260)
  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:1149)
  at org.apache.hadoop.mapred.Child.main(Child.java:249)
  </code></pre>
  
  <p>Has anyone any ideas of what might be causing this?</p>
  
  <p><strong>Edit: Solved it myself.</strong>
  If anyone else runs into the same problem, this was caused by the etc/hosts file on the master-node. I hadn´t entered the host-name and address of the slave-node. 
  This is how my hosts-file is structured on the master-node:</p>
  
  <pre><code>    127.0.0.1   MyUbuntuServer
      192.xxx.x.xx2   master
      192.xxx.x.xx3   MySecondUbuntuServer
      192.xxx.x.xx3   slave
  </code></pre>