To test whether your Flume HDFS sink is properly configured to connect to your secure HDFS cluster, you must run data through Flume. An easy way to do this is to configure a Netcat source, a Memory channel, and an HDFS sink. Start Flume with that configuration, and use the nc command (available freely online and with many UNIX distributions) to send events to the Netcat source port. The resulting events should appear on HDFS in the configured location. If the events do not appear, check the Flume log at /var/log/flume-ng/flume.log for any error messages related to Kerberos.