2.2. Decommission TaskTrackers

Use the following instructions to decommission TaskTrackers in your cluster:

On the NameNode host machine, edit the $HADOOP_CONF_DIR/mapred.exclude file and add the list of TaskTrackers hostnames (separated by newline character).
where $HADOOP_CONF_DIR is the directory for storing the Hadoop configuration files. For example, /etc/hadoop/conf.
Update the JobTracker with the new set of permitted TaskTrackers. On the JobTracker host machine, execute the following command:
```
su - $MAPRED_USER
% hadoop mradmin –refreshNodes
```
where $MAPRED_USER is the user owning the MapReduce services. For example, mapred.