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Hadoop, mail # user - configuration and FileSystem


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Re: configuration and FileSystem
Allen Wittenauer 2011-05-10, 17:46

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.