Hadoop configuration properties
Before we look at running the cluster, let's talk a little about Hadoop's configuration properties. We have been introducing many of these along the way, and there are a few additional points worth considering.
Default values
One of the most mystifying things to a new Hadoop user is the large number of configuration properties. Where do they come from, what do they mean, and what are their default values?
If you have the full Hadoop distribution—that is, not just the binary distribution—the following XML files will answer your questions:
Hadoop/src/core/core-default.xmlHadoop/src/hdfs/hdfs-default.xmlHadoop/src/mapred/mapred-default.xml
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