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Date: Sun, 6 Jun 2010 10:00:32 +0800
Message-ID: <AANLkTikgnqQyHEUpt8T5bQwnSdQVVoKedRBInoHhYvju@mail.gmail.com>
Subject: Several questions about Hadoop
From: Kevin Tse <kevintse.onjee@gmail.com>
To: common-user@hadoop.apache.org
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Hello,
I have successfully run Hadoop on a cluster of 3 nodes on RedHat linux, I
have several questions to ask.

1. When I submit an MR job using "hadoop jar mr-job.jar", it starts printing
out log messages to the stdout, how do I make it run in the
background?("hadoop jar mr-job.jar > log &" does not work). If it can be put
in the background, where do I find those log messages that it used to print
to the stdout?
2. While the MR job is being executed, will the MR job process be
affected/killed if I press "Ctrl-c"? it seems not since I can see the
tasktracker is still running, but I am not sure.
3. While the MR job is being executed, if I stop one of the
tasktrackers/nodes in the cluster using hadoop-daemon.sh, will the result of
the maps and reduces semi-completed by that tasktracker/node be submitted to
the namenode to be merged with the results completed by other tasktrackers?
Is it possible to restart a tasktracker at a point where it was stopped?

Thank you in advance.
- Kevin Tse

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