Book Image

Hadoop 2.x Administration Cookbook

By : Aman Singh
Book Image

Hadoop 2.x Administration Cookbook

By: Aman Singh

Overview of this book

Hadoop enables the distributed storage and processing of large datasets across clusters of computers. Learning how to administer Hadoop is crucial to exploit its unique features. With this book, you will be able to overcome common problems encountered in Hadoop administration. The book begins with laying the foundation by showing you the steps needed to set up a Hadoop cluster and its various nodes. You will get a better understanding of how to maintain Hadoop cluster, especially on the HDFS layer and using YARN and MapReduce. Further on, you will explore durability and high availability of a Hadoop cluster. You’ll get a better understanding of the schedulers in Hadoop and how to configure and use them for your tasks. You will also get hands-on experience with the backup and recovery options and the performance tuning aspects of Hadoop. Finally, you will get a better understanding of troubleshooting, diagnostics, and best practices in Hadoop administration. By the end of this book, you will have a proper understanding of working with Hadoop clusters and will also be able to secure, encrypt it, and configure auditing for your Hadoop clusters.
Table of Contents (20 chapters)
Hadoop 2.x Administration Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface
Index

Recovering deleted files


In this recipe, we will look at how we can recover deleted files from the Hadoop cluster. What if the user deletes a critical file with the -skipTrash option? Can it be recovered?

This recipe, is more of a best effort to restore the files after deletion. When the delete command is executed, the Namenode updates its metadata in edits file and then fires the invalidate command to remove the blocks. If the cluster is very busy, the invalidation might take time and we can revoke the files. But, on an idle cluster, if we delete the files, Namenode will immediately fire the invalidate command in response to the Datanode heartbeat and as Datanode does not have any pending operations to do, it will delete the blocks.

Getting ready

Make sure that the user has a running cluster with at least HDFS configured and working perfectly.

How to do it...

  1. Connect to the master1.cyrus.com master node and switch to user hadoop.

  2. Create any file and copy it to HDFS. Then, delete that file using...