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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Sun, 17 Jul 2011 12:12:42 -0000
Message-ID: <20110717121242.42913.23018@eos.apache.org>
Subject: =?utf-8?q?=5BHadoop_Wiki=5D_Update_of_=22FAQ=22_by_QwertyManiac?=
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The "FAQ" page has been changed by QwertyManiac:
http://wiki.apache.org/hadoop/FAQ?action=3Ddiff&rev1=3D106&rev2=3D107

Comment:
hadoop.tmp.dir explained

  If you find something that you wish were done better, and know how to fix=
 it, read HowToContribute, and contribute a patch.
  =

  =3D=3D I am seeing connection refused in the logs.  How do I troubleshoot=
 this? =3D=3D
- See ConnectionRefused .
+ See ConnectionRefused
+ =

+ =3D=3D Why is the 'hadoop.tmp.dir' config default user.name dependent? =
=3D=3D
+ =

+ We need a directory that a user can write and also not to interfere with =
other users.  =

+ If we didn't include the username, then different users would share the s=
ame tmp directory.  =

+ This can cause authorization problems, if folks' default umask doesn't pe=
rmit write by others.  =

+ It can also result in folks stomping on each other, when they're, e.g., p=
laying with HDFS and
+ re-format their filesystem.
  =

  =3D=3D Does Hadoop require SSH? =3D=3D
  Hadoop provided scripts (e.g., start-mapred.sh and start-dfs.sh) use ssh =
in order to start and stop the various daemons and some other utilities. Th=
e Hadoop framework in itself does not '''require''' ssh. Daemons (e.g. Task=
Tracker and DataNode) can also be started manually on each node without the=
 script's help.