Thanks for your replies.   I did not touch the cluster for few days. Now i fixed the problem. May be the memory settings helped a little : i installed node manager also on my Name Node and fixed key: yarn.nodemanager.resource.memory-mb to 3GB but actually set the max container size to 2GB.   It appears in the logs of Node Manager i had a trouble with this :     <property>     <description>Where to aggregate logs to.</description>     <name>yarn.nodemanager.remote-app-log-dir</name>     <value>hdfs://namenode.*****.com:8020</value>   </property>   so i just let it as default by deleting this key setting. Now it works !   See the beautiful result of my Pi example   asimon@namenode:/etc/hadoop/conf$ sudo -u mapred hadoop jar /usr/lib/hadoop-mapreduce/hadoop-mapreduce-examples-2.5.0-cdh5.2.0.jar pi 2 2 Number of Maps = 2 Samples per Map = 2 Wrote input for Map #0 Wrote input for Map #1 Starting Job 14/11/28 15:27:31 INFO client.RMProxy: Connecting to ResourceManager at namenode.beijaflore.com/192.168.54.111:8032 14/11/28 15:27:31 INFO input.FileInputFormat: Total input paths to process : 2 14/11/28 15:27:31 INFO mapreduce.JobSubmitter: number of splits:2 14/11/28 15:27:31 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1417184716260_0001 14/11/28 15:27:32 INFO impl.YarnClientImpl: Submitted application application_1417184716260_0001 14/11/28 15:27:32 INFO mapreduce.Job: The url to track the job: http://namenode.beijaflore.com:8088/proxy/application_1417184716260_0001/ 14/11/28 15:27:32 INFO mapreduce.Job: Running job: job_1417184716260_0001 14/11/28 15:27:41 INFO mapreduce.Job: Job job_1417184716260_0001 running in uber mode : false 14/11/28 15:27:41 INFO mapreduce.Job: map 0% reduce 0% 14/11/28 15:27:46 INFO mapreduce.Job: map 50% reduce 0% 14/11/28 15:27:53 INFO mapreduce.Job: map 100% reduce 0% 14/11/28 15:27:54 INFO mapreduce.Job: map 100% reduce 100% 14/11/28 15:27:55 INFO mapreduce.Job: Job job_1417184716260_0001 completed successfully 14/11/28 15:27:55 INFO mapreduce.Job: Counters: 49 File System Counters FILE: Number of bytes read=50 FILE: Number of bytes written=306673 FILE: Number of read operations=0 FILE: Number of large read operations=0 FILE: Number of write operations=0 HDFS: Number of bytes read=560 HDFS: Number of bytes written=215 HDFS: Number of read operations=11 HDFS: Number of large read operations=0 HDFS: Number of write operations=3 Job Counters Launched map tasks=2 Launched reduce tasks=1 Data-local map tasks=2 Total time spent by all maps in occupied slots (ms)=108368 Total time spent by all reduces in occupied slots (ms)=44920 Total time spent by all map tasks (ms)=13546 Total time spent by all reduce tasks (ms)=5615 Total vcore-seconds taken by all map tasks=13546 Total vcore-seconds taken by all reduce tasks=5615 Total megabyte-seconds taken by all map tasks=13871104 Total megabyte-seconds taken by all reduce tasks=5749760 Map-Reduce Framework Map input records=2 Map output records=4 Map output bytes=36 Map output materialized bytes=56 Input split bytes=324 Combine input records=0 Combine output records=0 Reduce input groups=2 Reduce shuffle bytes=56 Reduce input records=4 Reduce output records=0 Spilled Records=8 Shuffled Maps =2 Failed Shuffles=0 Merged Map outputs=2 GC time elapsed (ms)=142 CPU time spent (ms)=1800 Physical memory (bytes) snapshot=678866944 Virtual memory (bytes) snapshot=3176591360 Total committed heap usage (bytes)=454430720 Shuffle Errors BAD_ID=0 CONNECTION=0 IO_ERROR=0 WRONG_LENGTH=0 WRONG_MAP=0 WRONG_REDUCE=0 File Input Format Counters Bytes Read=236 File Output Format Counters Bytes Written=97 Job Finished in 24.739 seconds Estimated value of Pi is 4.00000000000000000000     Thank you again for your replies.. I'll continue to hang around here. Especialy when i get in trouble !     Miraculous     ... View more