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From "Kartashov, Andy" <Andy.Kartas...@mpac.ca>
Subject cluster set-up / directory structure or something that I was originally confused about
Date Tue, 06 Nov 2012 15:22:38 GMT

Last month I asked question 2 and this is what I have recently learned.

If you decide to overwrite Hadoop default directories (recommended) this is what to keep in

You create directories:

A. On Local Linux FS, using $ mkdir:

1. What:
/home/hadoop/dfs/name (required if you are running  NameNode on this node)
/home/hadoop/dfs/data (required if you are running DataNode)
 /home/hadoop/dfs/namesecondary (required if you are running SNN)

Where to specify property:

NOTE: if you start NN/DN/SNN prior to creating those directories and modifying hdfs-site.xml
file, a /tmp/..-hdfs/dfs/[name/data/namesecondary]  will be created for you on your local
Linux file system.

2. What:
/home/mapred/local (required if you are running TT on this node)

Where to specify property :
NOTE: if you don't  create  this directory and modifying mapred-site.xml file, a /tmp/*/mapred
/local  will be created for you on your local Linux file system when you start TT Daemon.

B. On HDFS, using $sudo -u hdfs hadop fs -mkdir
1. What:
/var/...... (depending on your MapReduce)

2. What:
/home/hadoop/system (requires for the JT)
Where to specify property:
NOTE: if you start Job-Tracker Daemon on your NN before creating above directory. A default
directory will be created inside your HDFS - /tmp/hadop/mapred/system

Each folder requires proper ownership. DFS  needs hdfs:hadoop / MapReduce needs mapred:hadoop

Feel free to correct me if I am wrong.


-----Original Message-----
From: Kartashov, Andy
Sent: Friday, October 26, 2012 12:40 PM
To: user@hadoop.apache.org
Subject: cluster set-up / a few quick questions


- do you put Master's node <hostname> under fs.default.name in core-site.xml on the
slave machines or slaves' hostnames?
- do you need to run "sudo -u hdfs hadoop namenode -format" and create /tmp /var folders on
the HDFS of the slave machines that will be running only DN and TT or not? Do you still need
to create hadoop/dfs/name folder on the slaves?

In hdfs-site.xml for dfs.name.dir & dfs.data.dir properties  we specify  /hadoop/dfs/name
/hadoop/dfs/data  being  local linux NFS directories by running command "mkdir -p /hadoop/dfs/data"
but mapred.system.dir  property is to point to HDFS and not NFS  since we are running "sudo
-u hdfs hadoop fs -mkdir /tmp/mapred/system"??
If so and since it is exactly the same format  /far/boo/baz how does hadoop know which directory
is local on NFS or HDFS?

Would you please kindly reconfirm.

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