Hadoop-daemon.sh as stated by Tariq is used on each individual node. This will bring up the Map/Reduce cluster with Jobtracker running on the machine you ran the command on and Tasktrackers running on machines listed in the slaves file. Use start-mapred.sh on the machine you plan to run the Jobtracker on. This will bring up HDFS with the Namenode running on the machine you ran the command on and Datanodes on the machines listed in the slaves file. Use start-dfs.sh on the node you want the Namenode to run on. You will use start-all.sh on the master node and would start what is necessary on the slaves as well. where you would have all the services on the same node.The namenode is also the datanode and is the master node). You would use start-all.sh on a single node cluster (i.e. Start-all.sh/stop-all.sh has to be run on the master node On such a machine you would need start-mapred.sh to separately start the job tracker This will bring up HDFS with the Namenode running on the machine you ran the command on.

This will startup a Namenode, Datanode, Jobtracker and a Tasktracker on your machine.

Tor switch hadoop