Data Replication error in Hadoop

Question

I am implementing the Hadoop Single Node Cluster on my machine by following Michael Noll\'s tutorial and have come across data replication error:

Here\'s the full error

Answer 1

The solution that worked for me was to run namenode and datanode one by one and not together using bin/start-all.sh. What happens using this approach is that the error is clearly visible if you are having some problem setting the datanodes on the network and also many posts on stackoverflow suggest that namenode requires some time to start-off, therefore, it should be given some time to start before starting the datanodes. Also, in this case I was having problem with different ids of namenode and datanodes for which I had to change the ids of the datanode with same id as the namenode.

The step by step procedure will be:

1. Start the namenode bin/hadoop namenode. Check for errors, if any.
2. Start the datanodes bin/hadoop datanode. Check for errors, if any.
3. Now start the task-tracker, job tracker using 'bin/start-mapred.sh'