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Editorial Team
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Asked: 2026-05-23T03:31:17+00:00

I am trying to run sort example on Hadoop single-node cluster. First of all,

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I am trying to run sort example on Hadoop single-node cluster. First of all, I start the deamons:

hadoop@ubuntu:/home/user/hadoop$ bin/start-all.sh

Then I run the random writer example to generate the sequential files as input files.

hadoop@ubuntu:/home/user/hadoop$ bin/hadoop jar hadoop-*-examples.jar randomwriter rand

hadoop@ubuntu:/home/user/hadoop$ bin/hadoop jar hadoop-*-examples.jar randomwriter rand

Running 0 maps. 

Job started: Thu Mar 31 18:21:51 EEST 2011 
11/03/31 18:21:52 INFO mapred.JobClient: Running job: job_201103311816_0001 
11/03/31 18:21:53 INFO mapred.JobClient:  map 0% reduce 0% 
11/03/31 18:22:01 INFO mapred.JobClient: Job complete: job_201103311816_0001 
11/03/31 18:22:01 INFO mapred.JobClient: Counters: 0 
Job ended: Thu Mar 31 18:22:01 EEST 2011

The job took 9 seconds.

hadoop@ubuntu:/home/user/hadoop$ bin/hadoop jar hadoop-*-examples.jar sort rand rand-sort

Running on 1 nodes to sort from hdfs://localhost:54310/user/hadoop/randinto

hdfs://localhost:54310/user/hadoop/rand-sort with 1 reduces. 

Job started: Thu Mar 31 18:25:19 EEST 2011 
11/03/31 18:25:20 INFO mapred.FileInputFormat: Total input paths to process : 0 
11/03/31 18:25:20 INFO mapred.JobClient: Running job: job_201103311816_0002 
11/03/31 18:25:21 INFO mapred.JobClient:  map 0% reduce 0% 
11/03/31 18:25:32 INFO mapred.JobClient:  map 0% reduce 100% 
11/03/31 18:25:34 INFO mapred.JobClient: Job complete: job_201103311816_0002 
11/03/31 18:25:34 INFO mapred.JobClient: Counters: 9 
11/03/31 18:25:34 INFO mapred.JobClient:   Job Counters 
11/03/31 18:25:34 INFO mapred.JobClient:     Launched reduce tasks=1 
11/03/31 18:25:34 INFO mapred.JobClient:   FileSystemCounters 
11/03/31 18:25:34 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=96 
11/03/31 18:25:34 INFO mapred.JobClient:   Map-Reduce Framework 
11/03/31 18:25:34 INFO mapred.JobClient:     Reduce input groups=0 
11/03/31 18:25:34 INFO mapred.JobClient:     Combine output records=0 
11/03/31 18:25:34 INFO mapred.JobClient:     Reduce shuffle bytes=0 
11/03/31 18:25:34 INFO mapred.JobClient:     Reduce output records=0 
11/03/31 18:25:34 INFO mapred.JobClient:     Spilled Records=0 
11/03/31 18:25:34 INFO mapred.JobClient:     Combine input records=0 
11/03/31 18:25:34 INFO mapred.JobClient:     Reduce input records=0 
Job ended: Thu Mar 31 18:25:34 EEST 2011

The job took 14 seconds.

hadoop@ubuntu:/home/user/hadoop$ bin/hadoop dfs -cat rand-sort/part-00000

SEQ#”org.apache.hadoop.io.BytesWritable”org.apache.hadoop.io.BytesWritablej”��mY�&�٩�#

I’m new to Hadoop. Is everything I am doing correct, or am I doing something wrong? And my question is, how can I see that the generated data from the randomwritewr and the results from the sort example are correct? From where can I see them?

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1 Answer

  1. Editorial Team

    The problem is that your tasktracker isn’t started by the time you try to run the job, it doesn’t start up instantly. You can run bin/hadoop job -list-active-trackers to see if the tasktracker is up or not, it may take a moment to finish coming up. No tasktracker = no nodes to map the writer to.

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