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From Ted Dunning <tdunn...@maprtech.com>
Subject Re: Entropy Pool and HDFS FS Commands Hanging System
Date Tue, 04 Jan 2011 00:41:48 GMT

   dd if=/dev/random bs=1 count=100 of=/dev/null

This will likely hang for a long time.

There is no way that I know of to change the behavior of /dev/random except
by changing the file itself to point to a different minor device.  That
would be very bad form.

One think you may be able do is to pour lots of entropy into the system via
/dev/urandom.  I was not able to demonstrate this, though, when I just tried
that.  It would be nice if there were a config variable to set that would
change this behavior, but right now, a code change is required (AFAIK).

Another thing to do is replace the use of SecureRandom with a version that
uses /dev/urandom.  That is the point of the code that I linked to.  It
provides a plugin replacement that will not block.

On Mon, Jan 3, 2011 at 4:31 PM, Jon Lederman <jon2718@gmail.com> wrote:

> Could you give me a bit more information on how I can overcome this issue.
>  I am running Hadoop on an embedded processor and networking is turned off
> to the embedded processor. Is there a quick way to check whether this is in
> fact blocking on my system?  And, are there some variables or configuration
> options I can set to avoid any potential blocking behavior?

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