Hadoop : MapReduce : port 8020 failed on connection exception

Error when running MapReduce :

[hadoop@hadoopmaster1 ~]$ /usr/lib/hadoop/bin/hadoop jar /usr/lib/hadoop-mapreduce/hadoop-mapreduce-examples-*.jar teragen 100 tmp/teragenout

:

:

:

Caused by: java.net.ConnectException: Call From hadoopmaster1/192.168.1.187 to hadoopmaster1:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused

Solution : Restart HDFS Name Node

[hdfs@hadoopmaster1 ~]$jps
32192 DataNode

su hdfs

stop

/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR stop namenode

/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR stop secondarynamenode

/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR stop datanode

start

/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start namenode

/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start secondarynamenode

/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start datanode

[hdfs@hadoopmaster1 ~]$jps

32192 DataNode

31851 NameNode

[root@hadoopmaster1 conf]# netstat -lent | grep :8020

tcp        0      0 192.168.1.187:8020          0.0.0.0:*                   LISTEN      493        548347

[hadoop@hadoopmaster1 ~]$ /usr/lib/hadoop/bin/hadoop jar /usr/lib/hadoop-mapreduce/hadoop-mapreduce-examples-*.jar teragen 10 tmp/teragenout

java.io.IOException: Output directory tmp/teragenout already exists.

[hadoop@hadoopmaster1 ~]$ /usr/lib/hadoop/bin/hadoop jar /usr/lib/hadoop-mapreduce/hadoop-mapreduce-examples-*.jar teragen 10 tmp/teragenout2

14/09/09 21:25:26 INFO client.RMProxy: Connecting to ResourceManager at hadoopmaster1/192.168.1.187:8050

14/09/09 21:25:29 INFO terasort.TeraSort: Generating 10 using 2

14/09/09 21:25:29 INFO mapreduce.JobSubmitter: number of splits:2

14/09/09 21:25:30 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1410306715808_0002

14/09/09 21:25:32 INFO impl.YarnClientImpl: Submitted application application_1410306715808_0002

14/09/09 21:25:33 INFO mapreduce.Job: The url to track the job: http://hadoopmaster1:8088/proxy/application_1410306715808_0002/

14/09/09 21:25:33 INFO mapreduce.Job: Running job: job_1410306715808_0002

14/09/09 21:26:04 INFO mapreduce.Job: Job job_1410306715808_0002 running in uber mode : false

14/09/09 21:26:05 INFO mapreduce.Job:  map 0% reduce 0%

14/09/09 21:26:49 INFO mapreduce.Job:  map 100% reduce 0%

14/09/09 21:26:56 INFO mapreduce.Job: Job job_1410306715808_0002 completed successfully

14/09/09 21:26:57 INFO mapreduce.Job: Counters: 31

        File System Counters

                FILE: Number of bytes read=0

                FILE: Number of bytes written=192632

                FILE: Number of read operations=0

                FILE: Number of large read operations=0

                FILE: Number of write operations=0

                HDFS: Number of bytes read=158

                HDFS: Number of bytes written=1000

                HDFS: Number of read operations=8

                HDFS: Number of large read operations=0

                HDFS: Number of write operations=4

        Job Counters

                Launched map tasks=2

                Other local map tasks=2

                Total time spent by all maps in occupied slots (ms)=264387

                Total time spent by all reduces in occupied slots (ms)=0

                Total time spent by all map tasks (ms)=88129

                Total vcore-seconds taken by all map tasks=88129

                Total megabyte-seconds taken by all map tasks=135366144

        Map-Reduce Framework

                Map input records=10

                Map output records=10

                Input split bytes=158

                Spilled Records=0

                Failed Shuffles=0

                Merged Map outputs=0

                GC time elapsed (ms)=399

                CPU time spent (ms)=3170

                Physical memory (bytes) snapshot=188051456

                Virtual memory (bytes) snapshot=2521628672

                Total committed heap usage (bytes)=31719424

        org.apache.hadoop.examples.terasort.TeraGen$Counters

                CHECKSUM=24474895181

        File Input Format Counters

                Bytes Read=0

        File Output Format Counters

                Bytes Written=1000