Create a topology script and data file. The topology script must be executable.

Sample Topology Script Named rack-topology.sh

#!/bin/bash

# Adjust/Add the property "net.topology.script.file.name"
# to core-site.xml with the "absolute" path the this
# file. ENSURE the file is "executable".

# Supply appropriate rack prefix
RACK_PREFIX=default

# To test, supply a hostname as script input:
if [ $# -gt 0 ]; then

CTL_FILE=${CTL_FILE:-"rack_topology.data"}

HADOOP_CONF=${HADOOP_CONF:-"/etc/hadoop/conf"} 

if [ ! -f ${HADOOP_CONF}/${CTL_FILE} ]; then
 echo -n "/$RACK_PREFIX/rack "
 exit 0
fi

while [ $# -gt 0 ] ; do
 nodeArg=$1
 exec< ${HADOOP_CONF}/${CTL_FILE}
 result=""
 while read line ; do
 ar=( $line )
 if [ "${ar[0]}" = "$nodeArg" ] ; then
 result="${ar[1]}"
 fi
 done
 shift
 if [ -z "$result" ] ; then
 echo -n "/$RACK_PREFIX/rack "
 else
 echo -n "/$RACK_PREFIX/rack_$result "
 fi
done

else
 echo -n "/$RACK_PREFIX/rack "
fi

Sample Topology Data File Named rack_topology.data

# This file should be:
# - Placed in the /etc/hadoop/conf directory
# - On the Namenode (and backups IE: HA, Failover, etc)
# - On the Job Tracker OR Resource Manager (and any Failover JT's/RM's) 
# This file should be placed in the /etc/hadoop/conf directory.

# Add Hostnames to this file. Format <host ip> <rack_location>
192.168.2.10 01
192.168.2.11 02
192.168.2.12 03

Copy both of these files to the /etc/hadoop/conf directory on all cluster nodes.

Run the rack-topology.sh script to ensure that it returns the correct rack information for each host.