how to setup a hadoop node to be a tasktracker but not a datanode

For a special re开发者_StackOverflow社区ason, I want to setup a hadoop node to be a tasktracker but not a datanode. It seems like there is a way to do it but I have not been able too. Could someone give me a hand? Thanks.

You have to setup a host-exclude file for your namenode. This edit in the core-site.xml:

<property>
  <name>dfs.hosts.exclude</name>
  <value>YOUR_PATH_TO_THE_EXCLUDE_FILE</value>
</property>

This file is basically like a slave or master file. You have to just insert the hostname like:

host1
host2

When restarting the namenode will ignore these given hosts but the jobtracker will launch a tasktracker.