1. Create a Rack Topology Script

Create a topology script and data file.

Sample Topology Script

File name: rack-topology.sh

HADOOP_CONF=/etc/hadoop/conf 

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

Sample Topology Data File

File name: topology.data

hadoopdata1.ec.com     /dc1/rack1
hadoopdata1            /dc1/rack1
10.1.1.1               /dc1/rack2

Copy both of these files to /etc/hadoop/conf.

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