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Message-ID: <4850A2F5.6090708@apache.org>
Date: Wed, 11 Jun 2008 21:15:49 -0700
From: Doug Cutting <cutting@apache.org>
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To: core-user@hadoop.apache.org
Subject: Re: client connect as different username?
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Sender: Doug Cutting <cutting@gmail.com>

Chris Collins wrote:
> You are referring to creating a directory in hdfs?  Because if I am user 
> chris and the hdfs only has user foo, then I cant create a directory 
> because I dont have perms, infact I cant even connect.

Today, users and groups are declared by the client.  The namenode only 
records and checks against user and group names provided by the client. 
  So if someone named "foo" writes a file, then that file is owned by 
someone named "foo" and anyone named "foo" is the owner of that file. 
No "foo" account need exist on the namenode.

The one (important) exception is the "superuser".  Whatever user name 
starts the namenode is the superuser for that filesystem.  And if "/" is 
not world writable, a new filesystem will not contain a home directory 
(or anywhere else) writable by other users.  So, in a multiuser Hadoop 
installation, the superuser needs to create home directories and project 
directories for other users and set their protections accordingly before 
other users can do anything.  Perhaps this is what you've run into?

Doug