If your cluster does not have excludes file, add it in hdfs-site.xml

<property>
  <name>dfs.hosts.exclude</name>
  <value>/usr/local/hadoop/conf/excludes</value>
  <description>Names a file that contains a list of hosts excluded from cluster</description> </property>

Add hostname of the node you want to remove to mapred.exclude
Add hostname of the node you want to remove to hdfs.exclude
Notify the JobTracker to re-read the exclude list and disconnect the worker node which will be removed

$ hadoop mradmin -refreshNodes


Notify the NameNode to re-read the exclude list and disconnect the worker node which will be removed

$ hadoop dfsadmin -refreshNodes

Monitor the removal process

$ hadoop dfsadmin -report