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The "FAQ" page has been changed by QwertyManiac: http://wiki.apache.org/hadoop/FAQ?action=diff&rev1=106&rev2=107 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. == I am seeing connection refused in the logs. How do I troubleshoot this? == - See ConnectionRefused . + See ConnectionRefused + + == Why is the 'hadoop.tmp.dir' config default user.name dependent? == + + 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 same tmp directory. + This can cause authorization problems, if folks' default umask doesn't permit write by others. + It can also result in folks stomping on each other, when they're, e.g., playing with HDFS and + re-format their filesystem. == Does Hadoop require SSH? == 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. The Hadoop framework in itself does not '''require''' ssh. Daemons (e.g. TaskTracker and DataNode) can also be started manually on each node without the script's help.
