This is the documentation for CDH 4.7.1.
Documentation for other versions is available at Cloudera Documentation.

Step 5: Shut Down the Cluster

To enable security in CDH, you must stop all Hadoop daemons in your cluster and then change some configuration properties. You must stop all daemons in the cluster because after one Hadoop daemon has been restarted with the configuration properties set to enable security, daemons running without security enabled will be unable to communicate with that daemon. This requirement to shut down all daemons makes it impossible to do a rolling upgrade to enable security on a Hadoop cluster.

To shut down the cluster, run the following command on every node in your cluster (as root):

$ for x in `cd /etc/init.d ; ls hadoop-*` ; do sudo service $x stop ; done