Top 50 interview questions and answers for hadoop

1. What is Hadoop?

Hadoop is an open-source software framework used for storing and processing large datasets.

2. What are the components of Hadoop?

The components of Hadoop are HDFS (Hadoop Distributed File System), MapReduce, and YARN (Yet Another Resource Negotiator).

3. What is HDFS?

HDFS is a distributed file system used for storing large datasets across multiple machines.

4. What is MapReduce?

MapReduce is a programming model used for processing large datasets in parallel.

5. What is YARN?

YARN is a resource management system used for managing resources in a Hadoop cluster.

6. What is the difference between HDFS and MapReduce?

HDFS is used for storing data, while MapReduce is used for processing data.

7. What is a NameNode?

A NameNode is a component of HDFS that manages the file system namespace and regulates access to files.

8. What is a DataNode?

A DataNode is a component of HDFS that stores data in the form of blocks.

9. What is a JobTracker?

A JobTracker is a component of MapReduce that manages the processing of jobs.

10. What is a TaskTracker?

A TaskTracker is a component of MapReduce that executes tasks assigned by the JobTracker.

11. What is a block in HDFS?

A block is a unit of data stored in HDFS.

12. What is the default block size in HDFS?

The default block size in HDFS is 128 MB.

13. What is a rack in HDFS?

A rack is a collection of DataNodes that are physically close to each other.

14. What is a speculative execution in Hadoop?

Speculative execution is a feature in Hadoop that allows the system to launch multiple instances of a task to improve performance.

15. What is a combiner in MapReduce?

A combiner is a function used to aggregate intermediate data before sending it to the reducer.

16. What is a partitioner in MapReduce?

A partitioner is a function used to partition the output of the mapper before sending it to the reducer.

17. What is a reducer in MapReduce?

A reducer is a function used to aggregate the output of the mapper.

18. What is a shuffle in MapReduce?

A shuffle is the process of transferring data from the mapper to the reducer.

19. What is a join in MapReduce?

A join is a process of combining data from two or more sources based on a common key.

20. What is a distributed cache in Hadoop?

A distributed cache is a feature in Hadoop that allows the system to cache files across multiple nodes in a cluster.

21. What is a block scanner in HDFS?

A block scanner is a component of HDFS that scans blocks for errors.

22. What is a checkpoint in HDFS?

A checkpoint is a process of saving the metadata of the NameNode to a file.

23. What is a secondary NameNode in HDFS?

A secondary NameNode is a component of HDFS that helps in creating checkpoints.

24. What is a heartbeat in Hadoop?

A heartbeat is a signal sent by a node to indicate that it is still alive.

25. What is a speculative task in MapReduce?

A speculative task is a task launched by the system to improve performance.

26. What is a speculative execution in HDFS?

Speculative execution is a feature in HDFS that allows the system to launch multiple instances of a task to improve performance.

27. What is a block report in HDFS?

A block report is a report sent by a DataNode to the NameNode to indicate the status of its blocks.

28. What is a decommissioning in HDFS?

Decommissioning is a process of removing a DataNode from the cluster.

29. What is a replication factor in HDFS?

A replication factor is the number of copies of a block stored in HDFS.

30. What is a quota in HDFS?

A quota is a limit on the amount of disk space used by a user or a group.

31. What is a trash in HDFS?

A trash is a feature in HDFS that allows users to recover deleted files.

32. What is a snapshot in HDFS?

A snapshot is a read-only copy of a file system or a directory.

33. What is a distcp in Hadoop?

Distcp is a tool used for copying data between Hadoop clusters.

34. What is a pig in Hadoop?

Pig is a high-level platform used for creating MapReduce programs.

35. What is a hive in Hadoop?

Hive is a data warehousing tool used for querying and analyzing large datasets.

36. What is a hbase in Hadoop?

HBase is a NoSQL database used for storing and retrieving large datasets.

37. What is a zookeeper in Hadoop?

Zookeeper is a distributed coordination service used for managing Hadoop clusters.

38. What is a flume in Hadoop?

Flume is a tool used for collecting, aggregating, and moving large amounts of log data.

39. What is a sqoop in Hadoop?

Sqoop is a tool used for importing and exporting data between Hadoop and relational databases.

40. What is a oozie in Hadoop?

Oozie is a workflow scheduler used for managing Hadoop jobs.

41. What is a mahout in Hadoop?

Mahout is a machine learning library used for creating predictive models.

42. What is a spark in Hadoop?

Spark is a fast and general-purpose cluster computing system used for processing large datasets.

43. What is a yarn-site.xml in Hadoop?

Yarn-site.xml is a configuration file used for configuring YARN.

44. What is a core-site.xml in Hadoop?

Core-site.xml is a configuration file used for configuring HDFS.

45. What is a mapred-site.xml in Hadoop?

Mapred-site.xml is a configuration file used for configuring MapReduce.

46. What is a log4j.properties in Hadoop?

Log4j.properties is a configuration file used for configuring logging in Hadoop.

47. What is a namenode format in HDFS?

Namenode format is a process of formatting the NameNode.

48. What is a datanode format in HDFS?

Datanode format is a process of formatting the DataNode.

49. What is a job history server in Hadoop?

Job history server is a component of MapReduce that stores information about completed jobs.

50. What is a task attempt in MapReduce?

A task attempt is an instance of a task launched by the system.

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