Datanode failing in Hadoop on single Machine

I set up and configured sudo node hadoop environment on ubuntu 12.04 LTS using following tutorial http://www.michael-noll.com/tutorials/running-hadoop-on-ubuntu-linux-multi-node-cluster/#formatting-the-hdfs-filesystem-via-the-namenode

After typing hadoop/bin $ start-all.sh everything going fine then i checked the Jps then NameNode, JobTracker ,TaskTracker,SecondaryNode have been started but DataNode not started ...

If any know how to resolve this issue please let me know..

ya i resolved it...

java.io.IOException: Incompatible namespaceIDs

If you see the error java.io.IOException: Incompatible namespaceIDs in the logs of a DataNode (logs/hadoop-hduser-datanode-.log), chances are you are affected by issue HDFS-107 (formerly known as HADOOP-1212).

The full error looked like this on my machines: ... ERROR org.apache.hadoop.dfs.DataNode: java.io.IOException: Incompatible namespaceIDs in /app/hadoop/tmp/dfs/data: namenode namespaceID = 308967713; datanode namespaceID = 113030094 at org.apache.hadoop.dfs.DataStorage.doTransition(DataStorage.java:281) at org.apache.hadoop.dfs.DataStorage.recoverTransitionRead(DataStorage.java:121) at org.apache.hadoop.dfs.DataNode.startDataNode(DataNode.java:230) at org.apache.hadoop.dfs.DataNode.(DataNode.java:199) at org.apache.hadoop.dfs.DataNode.makeInstance(DataNode.java:1202) at org.apache.hadoop.dfs.DataNode.run(DataNode.java:1146) at org.apache.hadoop.dfs.DataNode.createDataNode(DataNode.java:1167) at org.apache.hadoop.dfs.DataNode.main(DataNode.java:1326) t the moment, there seem to be two workarounds as described below.

Workaround 1: Start from scratch I can testify that the following steps solve this error, but the side effects won’t make you happy (me neither). The crude workaround I have found is to:

Stop the cluster Delete the data directory on the problematic DataNode: the directory is specified by dfs.data.dir in conf/hdfs-site.xml; if you followed this tutorial, the relevant directory is /app/hadoop/tmp/dfs/data Reformat the NameNode (NOTE: all HDFS data is lost during this process!) Restart the cluster When deleting all the HDFS data and starting from scratch does not sound like a good idea (it might be ok during the initial setup/testing), you might give the second approach a try.

Workaround 2: Updating namespaceID of problematic DataNodes Big thanks to Jared Stehler for the following suggestion. I have not tested it myself yet, but feel free to try it out and send me your feedback. This workaround is “minimally invasive” as you only have to edit one file on the problematic DataNodes:

Stop the DataNode Edit the value of namespaceID in /current/VERSION to match the value of the current NameNode Restart the DataNode If you followed the instructions in my tutorials, the full path of the relevant files are:

NameNode: /app/hadoop/tmp/dfs/name/current/VERSION DataNode: /app/hadoop/tmp/dfs/data/current/VERSION (background: dfs.data.dir is by default set to ${hadoop.tmp.dir}/dfs/data, and we set hadoop.tmp.dir in this tutorial to /app/hadoop/tmp).

The solution for the problem is clearly given in the following site:

http://www.michael-noll.com/tutorials/running-hadoop-on-ubuntu-linux-multi-node-cluster/#java-io-ioexception-incompatible-namespaceids