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

Datanode troubleshooting


In this recipe, we will look at some of the common issues with Datanode and how to resolve them.

Getting ready

The user is expected to complete the previous recipe and must have completed the Setting up multi-node HBase cluster recipe in Chapter 9, HBase Administration. In this recipe, we will be using the already configured Hadoop cluster.

How to do it...

Scenario 1: Datanode not starting due to permission issues on the Datanode directory specified by dfs.datanode.data.dir:

  1. Connect to the dn1.cyrus.com master node in the cluster and change to user hadoop.

  2. Try to write a test file to the location using the following command:

    $ touch /space/dn1/test
    

    If it succeeds, then the permissions are fine.

  3. Otherwise, make sure the permissions of the directories pointed by dfs.datanode.data.dir are owned by the correct user. This is shown in the following screenshot:

  4. The user could be hadoop or hdfs. Also, the directory permission is 755 for the top directory, as shown in the following...