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From Allen Wittenauer ...@apache.org>
Subject Re: configuration and FileSystem
Date Tue, 10 May 2011 17:46:54 GMT

On May 10, 2011, at 9:57 AM, Gang Luo wrote:
> I was confused by the configuration and file system in hadoop. when we create a 
> FileSystem object and read/write something through it, are we writing to or 
> reading from HDFS?

	Typically, yes.

> Could it be local file system?

	Yes.


> If yes, what determines which 
> file system it is? Configuration object we used to create the FileSystem object?

	Yes.

> When I write mapreduce program which "extends Configured implements Tool", I can 
> get the right configuration by calling getConf() and use the FileSystem object 
> to communicate with HDFS. What if I want to read/write HDFS in a separate 
> Utility class? Where does the configuration come from?

	You need to supply it.



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