The configuration files that need to be updated to set up a fully distributed mode of Hadoop are:  Hadoop-env.sh  Core-site.xml  Hdfs-site.xml  Mapred-site.xml  Masters  Slaves  These files can be found in your Hadoop > conf directory. If Hadoop daemons are started individually with "bin/Hadoop-daemon.sh start xxxxxx', where xxxx is the name of the daemon, then the master and slave files do not need to be updated and can be empty. When starting daemons in this way, commands must be issued on the appropriate node to start the appropriate daemons. When Hadoop daemons are started with "bin/start-dfs.sh' and 'bin/start-mapred.sh', the master and slave configuration files must be updated on the NameNode machine.  Masters - IP address/hostname of the node on which SecondaryNameNode is run. Slaves - IP address/hostname of the node on which the DataNodes and possibly the task trackers will run.