Add the topology script property to core-site.xml

Assign the name of the topology script to the net.topology.script.file.name property in core-site.xml.

Stop the HDFS cluster.
Add the topology script file to core-site.xml.
In the following example, the value of the property net.topology.script.file.name is the name of the topology script file.
```
<property>
  <name>net.topology.script.file.name</name> 
  <value>/etc/hadoop/conf/rack-topology.sh</value>
</property>
```
By default, the topology script processes up to 100 requests per invocation. You can specify a number other than the default value with the net.topology.script.number.args property, as shown in the following example:
```
<property> 
  <name>net.topology.script.number.args</name> 
  <value>75</value>
</property>
```