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Hadoop Basic Interview Questions and Answers Part-2

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hadoop11. How to exit the Vi editor?

To exit the Vi Editor, press ESC and type :q and then press enter.

12. What is a spill factor with respect to the RAM?

Spill factor is the size after which your files move to the temp file. Hadoop-temp directory is used for this.

13. Is fs.mapr.working.dir a single directory?

Yes, fs.mapr.working.dir it is just one directory.

14. Which are the three main hdfs-site.xml properties?

The three main hdfs-site.xml properties are:

1. dfs.name.dir which gives you the location on which metadata will be stored and where DFS is located – on disk or onto the remote.

2. dfs.data.dir which gives you the location where the data is going to be stored.

3. fs.checkpoint.dir which is for secondary Namenode.

15. How to come out of the insert mode?

To come out of the insert mode, press ESC, type :q (if you have not written anything) OR type :wq (if you have written anything in the file) and then press ENTER.

16. What is Cloudera and why it is used?

Cloudera is the distribution of Hadoop. It is a user created on VM by default. Cloudera belongs to Apache and is used for data processing.

17. What happens if you get a ‘connection refused java exception’ when you type hadoopfsck /?

It could mean that the Namenode is not working on your VM.

We are using Ubuntu operating system with Cloudera, but from where we can download Hadoop or does it come by default with Ubuntu?

This is a default configuration of Hadoop that you have to download from Cloudera or from Edureka’s dropbox and the run it on your systems. You can also proceed with your own configuration but you need a Linux box, be it Ubuntu or Red hat. There are installation steps present at the Cloudera location or in Edureka’s Drop box. You can go either ways.

18. What does ‘jps’ command do?

This command checks whether your Namenode, datanode, task tracker, job tracker, etc are working or not.

19. How can I restart Namenode?

1. Click on stop-all.sh and then click on start-all.sh OR

2. Write sudo hdfs (press enter), su-hdfs (press enter), /etc/init.d/ha (press enter) and then /etc/init.d/hadoop-0.20-namenode start (press enter).

20. What is the full form of fsck?

Full form of fsck is File System Check.

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