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I am new to Hadoop and I was trying to install Single node standalone Hadoop in Ubuntu 14.04. I was following the Apache Hadoop Document and as it is given there, when I tried to run 

$ bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.0.jar grep input output 'dfs[a-z.]+'

I got the java.net.ConnectException message:

Call From a1409User/127.0.0.1 to localhost:9000 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused

I checked in http://wiki.apache.org/hadoop/ConnectionRefused where it has been asked to verify that there isn't an entry for hostname mapped to 127.0.0.1 or 127.0.1.1 in /etc/hosts. Though this point is not so clear to me, I tried by changing the given IP and mentioning the port number but no luck. I also checked with telnet:

$ telnet localhost 9000
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused

Please help me to solve the issue.

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  • Did you start the cluster with start-all.sh? Commented Sep 7, 2014 at 18:03
  • Yes I did. Also I checked the services by jps command Commented Sep 8, 2014 at 5:46
  • which hadoop version are you trying to install? please use the document of the same version Commented Sep 8, 2014 at 7:20
  • Hadoop version 2.5.0. I am using the doc of the same version (link given in question) Commented Sep 8, 2014 at 14:14
  • what is the output of jps? try using netstat to see if it is listening at 9000. also try setting up pseudo distributed as i did Commented Sep 8, 2014 at 14:23

3 Answers 3

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Try to format namenode. Also in your script input and output directories must be given. For example:

hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.0.jar grep /user/hadoop/hadoop-config /user/hadoop/output 'dfs[a-z.]+'

After that you can check the content in the output directory by:

hdfs dfs -ls /user/hadoop/output/

It should print output as follows:

Found 2 items -rw-r--r-- 3 hadoop supergroup 0 2014-09-05 07:55 /user/hadoop/output/_SUCCESS -rw-r--r-- 3 hadoop supergroup 179 2014-09-05 07:55 /user/hadoop/output/part-r-00000

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  1. Confirm you are in Local (Standalone) Mode. I think you are not in the Standalone mode.

May be you have tried the another step. Make sure you are not config the etc/hadoop/core-site.xml and etc/hadoop/hdfs-site.xml.

  1. If you are want to try Pseudo-Distributed Mode .

Try config the etc/hadoop/core-site.xml and etc/hadoop/hdfs-site.xml again.

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Make sure HDFS is online. Start it by $HADOOP_HOME/sbin/start-dfs.sh

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