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From "Owen O'Malley" <o...@yahoo-inc.com>
Subject Re: Configuration policy
Date Tue, 20 Jun 2006 22:12:13 GMT

On Jun 20, 2006, at 9:29 AM, Paul Sutter wrote:

> Speaking of configuration, is there any clear definition for the 
> purpose of
> mapred-default.xml? My understanding is that its an alternate, 
> misnamed,
> site-local configuration, but we're not sure what to do with it.
> Right now, we make all of our changes to hadoop-site.xml, then copy 
> that
> file to mapred-default.xml because we've heard that sometimes, that 
> file
> gets checked instead of hadoop-site.xml.
> Any help appreciated

My general approach is that only things that the user/application 
should never change are in hadoop-site. Largely, this is limited to the 
namenode/jobtracker addresses, port, and directories. Everything else 
goes into mapred-default.xml. This includes things like:


This happens because of the load order of the config files:

hadoop-default.xml, mapred-default.xml, job.xml, hadoop-site.xml.

so job.xml will override the default files, but NOT the hadoop-site. I 
think that mapred-default would be better named site-default or 

-- Owen

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