Time for action – starting Hadoop

Unlike the local mode of Hadoop, where all the components run only for the lifetime of the submitted job, with the pseudo-distributed or fully distributed mode of Hadoop, the cluster components exist as long-running processes. Before we use HDFS or MapReduce, we need to start up the needed components. Type the following commands; the output should look as shown next, where the commands are included on the lines prefixed by $:

1. Type in the first command:

   $ start-dfs.sh
   starting namenode, logging to /home/hadoop/hadoop/bin/../logs/hadoop-hadoop-namenode-vm193.out
   localhost: starting datanode, logging to /home/hadoop/hadoop/bin/../logs/hadoop-hadoop-datanode-vm193.out
   localhost: starting secondarynamenode, logging to /home/hadoop/hadoop/bin/../logs/hadoop-hadoop-secondarynamenode-vm193.out
   

2. Type in the second command:

   $ jps
   9550 DataNode
   9687 Jps
   9638 SecondaryNameNode
   9471 NameNode
   

3. Type in the third command:

   $ hadoop dfs -ls /
   Found 2 items
   drwxr-xr-x   - hadoop...