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...