Hadoop Cluster Interview Questions and Answers Updated

1. In Which directory Hadoop installed?




Apache Hadoop and Cloudera have the same directory structure. Hadoop installed in cd/usr/lib/hadoop

2. Which are three modes in which Hadoop can be run?
In Hadoop eco-system three different types of odes can be run are:
A. Standalone (Local) mode
B.Pseudo-distributed mode
C.Fully distributed ode

3. What are the features of Standalone mode in a Hadoop environment?
In Hadoop eco-system Standalone mode there are one of the modes there are no daemons and everything runs on a single JVM (Java Virtual Machine). There is no DFS(Distributed File System) and utilizes the local file system. Stand-alone mode is suitable only for running MapReduce programs during development.

4. Does Hadoop follow the UNIX pattern?
Yes, Hadoop follows UNIX Pattern.

5. What are the features of Pseudo distributed mode in a Hadoop environment?
In Hadoop eco-system, Pseudo distributed mode is used for both the QA environment and development. In the Pseudo distributed mode all the daemons run on the same machine.




6. Can we call VMs as Pseudos?
No, VMs are not Pseudos because of VM is different and Pseudos are only for Hadoop environment.

7. What are the features of Fully distributed mode in a Hadoop environment?
In Hadoop eco-system, the Fully distributed mode is used for Production, Development and QA environment. Where we have a number of machines forming the Hadoop cluster.

8. What are the default port numbers of Namenode, job tracker and task tracker in Hadoop eco-system?
The port number of Namenode is “50070” for job tracker “50030” and task tracker”50060″.

9. What is the Hadoop configuration files only for Hadoop Installation?
There are three files to configured for Hadoop:
1.core-site.xml
2.hdfs-site.xml
3.mapred-site.xml
These files are located in hadoop/conf/ directory

10. What happens if you get a “connection refused java exception” in Hadoop? check Hadoop fsck? What happened?
It means that the Name node is not working on your machine.

11. What does /etc/init.d do?
/etc/init.d specifies that where daemons are placed or to see the status of these daemons

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