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From "Owen O'Malley" <omal...@apache.org>
Subject Re: hadoop.job.ugi backwards compatibility
Date Mon, 13 Sep 2010 17:59:12 GMT
On Mon, Sep 13, 2010 at 10:05 AM, Todd Lipcon <todd@cloudera.com> wrote:

> This is not MR-specific, since the strangely named hadoop.job.ugi determines
> HDFS permissions as well.

Yeah, after I hit send, I realized that I should have used common-dev.
This is really a dev issue.

> "or the user must write a custom group mapper" above refers to this plugin
> capability. But I think most users do not want to spend the time to write
> (or even setup) such a plugin beyond the default shell-based mapping
> service.

Sure, which is why it is easiest to just have the (hopefully disabled)
user accounts on the jt/nn. Any installs > 100 nodes should be using
HADOOP-6864 to avoid the fork in the JT/NN.

> As someone who spends an awful lot of time doing downstream support of lots
> of different clusters, I actually disagree.

Normal applications never need to do doAs. They run as the default
user. This only comes up in servers that deal with multiple users. In
*that* context, it sucks having servers that only work in non-secure
mode. If some server X only works without security that sucks. Doing
doAs isn't harder, it is just different. Having two different
semantics models *will* cause lots of grief.

-- Owen

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