Namenode troubleshooting

In this recipe, we will see how to find issues with Namenode and resolve them. As this is a recipe book, we will keep the theory to a minimum, but users must understand the moto behind the commands and how the mentioned tools work.

Getting ready

To step through the recipes in this chapter, make sure you have gone through the steps to install Hadoop cluster with HDFS and YARN enabled. Make sure to use Multi-node Hadoop cluster for better understanding and troubleshooting practice.

It is assumed that the user has basic knowledge about networking fundamentals, Linux commands, and filesystem.

How to do it...

Scenario 1: Namenode not starting due to permission issues on the Namenode directory.

1. Connect to the master1.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. If it succeeds, then the permissions are fine:

   $ touch /data/namenode1/test
   

3. Otherwise, make sure the permission of the directory...