Book Image

Hadoop Real-World Solutions Cookbook - Second Edition

By : Tanmay Deshpande
Book Image

Hadoop Real-World Solutions Cookbook - Second Edition

By: Tanmay Deshpande

Overview of this book

Big data is the current requirement. Most organizations produce huge amount of data every day. With the arrival of Hadoop-like tools, it has become easier for everyone to solve big data problems with great efficiency and at minimal cost. Grasping Machine Learning techniques will help you greatly in building predictive models and using this data to make the right decisions for your organization. Hadoop Real World Solutions Cookbook gives readers insights into learning and mastering big data via recipes. The book not only clarifies most big data tools in the market but also provides best practices for using them. The book provides recipes that are based on the latest versions of Apache Hadoop 2.X, YARN, Hive, Pig, Sqoop, Flume, Apache Spark, Mahout and many more such ecosystem tools. This real-world-solution cookbook is packed with handy recipes you can apply to your own everyday issues. Each chapter provides in-depth recipes that can be referenced easily. This book provides detailed practices on the latest technologies such as YARN and Apache Spark. Readers will be able to consider themselves as big data experts on completion of this book. This guide is an invaluable tutorial if you are planning to implement a big data warehouse for your business.
Table of Contents (18 chapters)
Hadoop Real-World Solutions Cookbook Second Edition
Credits
About the Author
Acknowledgements
About the Reviewer
www.PacktPub.com
Preface
Index

Exporting HDFS data to a local machine


In this recipe, we are going to export/copy data from HDFS to the local machine.

Getting ready

To perform this recipe, you should already have a running Hadoop cluster.

How to do it...

Performing this recipe is as simple as copying data from one folder to the other. There are a couple of ways in which you can export data from HDFS to the local machine.

  • Using the copyToLocal command, you'll get this code:

    hadoop fs -copyToLocal /mydir1/LICENSE.txt /home/ubuntu
    
  • Using the get command, you'll get this code:

    hadoop fs -get/mydir1/LICENSE.txt /home/ubuntu
    

How it works...

When you use HDFS copyToLocal or the get command, the following things occur:

  1. First of all, the client contacts NameNode because it needs a specific file in HDFS.

  2. NameNode then checks whether such a file exists in its FSImage. If the file is not present, the error code is returned to the client.

  3. If the file exists, NameNode checks the metadata for blocks and replica placements in DataNodes.

  4. NameNode...