How to see Logger Debug messages in Hadoop Map Reduce program while executing.

If your programing has Logger like below.

final static org.slf4j.Logger log = LoggerFactor.getLogger(MyMapperProgram.class);

and if you have written any debug messages,

using logger.debug("Hey i am here")

Now, if you want to see this message, normal logger properties or overriding any logger property from command will not be sufficient,

You can execute below command, before running the job in command line.

export HADOOP_ROOT_LOGGER="DEBUG,console"

With this you will be able to see the debug messages.