Namenode roll edits – offline mode

In this recipe, we will look at how to roll edits in offline mode. What if the Namenode disk is completely full and it is not able to start at all? We cannot use the process described in the precious recipe.

For this, we will use another Namenode, mount the NFS mount there, and perform the process there.

Getting ready

For this recipe, make sure you have completed the recipe on Hadoop cluster setup, Chapter 1, Hadoop Architecture and Deployment, and has one more node to use as just Namenode.

How to do it...

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

2. Unmount the NFS share, which is used as a directory to store the metadata as shown in the following screenshot:

   

3. Again, we are keeping the other mount point /data/namenode1 safe this time and just playing around with /data/namenode2.

4. Mount the NFS share on the master2.cyrus.com node using the following command:

   # mount –t nfs4 filer.cyrus.com:/nfs /mnt
   

5. On master2, create a directory owned by...