title: Missing block in Hadoop
body: <p>I am trying to run a wordcount job in Hadoop. Due to a previous error, I had to turn off the safe mode for the NameNode. Now, however, when trying to run the job, I am getting the following error:</p>
  
  <pre><code>14/08/06 14:49:08 INFO mapreduce.Job:  map 1% reduce 0%
  14/08/06 14:49:25 INFO mapreduce.Job: Task Id : attempt_1407336345567_0002_m_000158_0, Status : FAILED
  Error: org.apache.hadoop.hdfs.BlockMissingException: Could not obtain block: BP-971868671-192.168.50.2-1406571670535:blk_1073743276_2475 file=/wikidumps/enwiki-20130904-pages-meta-history3.xml-p000032706p000037161
      at org.apache.hadoop.hdfs.DFSInputStream.chooseDataNode(DFSInputStream.java:838)
      at org.apache.hadoop.hdfs.DFSInputStream.blockSeekTo(DFSInputStream.java:526)
      at org.apache.hadoop.hdfs.DFSInputStream.readWithStrategy(DFSInputStream.java:749)
      at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:793)
      at java.io.DataInputStream.read(DataInputStream.java:100)
      at org.apache.hadoop.util.LineReader.readDefaultLine(LineReader.java:211)
      at org.apache.hadoop.util.LineReader.readLine(LineReader.java:174)
      at org.apache.hadoop.mapreduce.lib.input.LineRecordReader.nextKeyValue(LineRecordReader.java:164)
      at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.nextKeyValue(MapTask.java:532)
      at org.apache.hadoop.mapreduce.task.MapContextImpl.nextKeyValue(MapContextImpl.java:80)
      at org.apache.hadoop.mapreduce.lib.map.WrappedMapper$Context.nextKeyValue(WrappedMapper.java:91)
      at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
      at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:763)
      at org.apache.hadoop.mapred.MapTask.run(MapTask.java:339)
      at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:162)
      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:1491)
      at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:157)
  </code></pre>
  
  <p>The log files are not showing any particular error. Does anyone know the reason for this error? Thanks in advance!</p>