Storing and Configuring Data with Hadoop, YARN, and ZooKeeper - Big Data Made Easy: A Working Guide to the Complete Hadoop Toolset - page 29

Clearly, the Hadoop V1 installation is working and can run a Map Reduce task. (The word-count algorithm does
not seem to strip out characters like quotation marks; this is not an issue for our purposes here, but might be if you
wanted a truly accurate count of the number of times Poe used particular words.)
Hadoop User Interfaces
Up to this point you have installed the release, configured it, and run a simple Map Reduce task to prove that it is
working. But how can you visually examine the Hadoop distributed file system or determine the state of the Hadoop
servers? Well, Hadoop provides a set of built-in user interfaces for this purpose. They are quite basic, but it is
worthwhile knowing about them. (In a large production system, of course, you would use one of the more functional
systems like Ambari for monitoring.)
In this example configuration, you can find the name node UI on port 50070 with a URL of http://hc1nn:50070/
(on the name node hc1nn). This port was defined via the value of the dfs.http.address in the configuration file hdfs-
site.xml. The name node UI shows storage information and node basics, as illustrated in Figure 2-3 . It is also possible
to browse the Hadoop file system and logs to determine the state of the nodes. The levels of HDFS storage used and
free can also be determined.