Storing and Configuring Data with Hadoop, YARN, and ZooKeeper - Big Data Made Easy: A Working Guide to the Complete Hadoop Toolset - page 21

The example configuration file here is for the server hc1r1m1. When the configuraton is changed to a cluster,
these Job Tracker entries will refer to Name Node machine hc1nn.

6. Set up file conf/hdfs-site.xml
Set up the basic configuration for the HDFS, adding the following between the configuration tags. This defines the
replication level for the HDFS; it shows that a single block will be copied twice. It also specifies the address of the
Name Node web user interface as dfs.http.address:

<property>
<name>dfs.replication</name>
<value>3</value>
<description>The replication level</description>
</property>
<property>
<name>dfs.http.address</name>
<value>http://localhost:50070/</value>
</property>

7. Format the file system
Run the following command as the Hadoop user to format the file system:
hadoop namenode -format

■ Warning do not execute this command on a running hdfS or you will lose your data!

The output should look like this:

14/03/15 16:08:19 INFO namenode.NameNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG: host = hc1nn/192.168.1.107
STARTUP_MSG: args = [-format]
STARTUP_MSG: version = 1.2.1
STARTUP_MSG: build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2 -r
1503152; compiled by 'mattf' on Mon Jul 22 15:23:09 PDT 2013
STARTUP_MSG: java = 1.6.0_30
************************************************************/
14/03/15 16:08:20 INFO util.GSet: Computing capacity for map BlocksMap
14/03/15 16:08:20 INFO util.GSet: VM type = 32-bit
14/03/15 16:08:20 INFO util.GSet: 2.0% max memory = 1013645312
14/03/15 16:08:20 INFO util.GSet: capacity = 2^22 = 4194304 entries
14/03/15 16:08:20 INFO util.GSet: recommended=4194304, actual=4194304
14/03/15 16:08:20 INFO namenode.FSNamesystem: fsOwner=hadoop
14/03/15 16:08:20 INFO namenode.FSNamesystem: supergroup=supergroup
14/03/15 16:08:20 INFO namenode.FSNamesystem: isPermissionEnabled=true
14/03/15 16:08:20 INFO namenode.FSNamesystem: dfs.block.invalidate.limit=100