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courses:mapreduce-tutorial:step-9 [2012/01/25 15:56]
straka 		courses:mapreduce-tutorial:step-9 [2012/01/25 16:07]
straka
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 The Hadoop itself uses many configuration options. Every option has a (dot-separated) name and a value and can be set on the command line using ''-Dname=value'' syntax: The Hadoop itself uses many configuration options. Every option has a (dot-separated) name and a value and can be set on the command line using ''-Dname=value'' syntax:
   perl script.pl run [-jt cluster_master | -c cluster_size [-w sec_to_wait]] [-r number_of_reducers] [Hadoop options] input_path output_path   perl script.pl run [-jt cluster_master | -c cluster_size [-w sec_to_wait]] [-r number_of_reducers] [Hadoop options] input_path output_path
-Mind that the order of options matters -- the ''-jt'', ''-c'', ''-w'' and ''-r'' must precede Hadoop options. +Mind that the order of options matters -- the ''-jt'', ''-c'', ''-w'' and ''-r'' must precede Hadoop options to be recognized.
  
 +Every Hadoop option has a read-only default. These are overridden by cluster specific options. Lastly, all of these are overriden by job specific options given on the command line (or set using the Java API).
  
 +==== Mapping of Perl options to Hadoop ====
 +^ Perl options ^ Hadoop options ^
 +| no options \\ (running locally) | ''-Dmapred.job.tracker=local'' \\ ''-Dmapred.local.dir=hadoop-localrunner-tmp'' \\ ''-Dhadoop.tmp.dir=hadoop-localrunner-tmp'' |
 +| ''-jt cluster_master'' | ''-Dmapred.job.tracker=cluster_master'' |
 +| ''-c cluster_machines'' | configuration of new cluster contains \\ ''-Dmapred.job.tracker=cluster_master'' |
 +| ''-r number_of_reducers'' | ''-Dmapred.reduce.tasks=number_of_reducers'' |

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