Hadoop: java.io.IOException: Incompatible namespaceIDs

The error java.io.IOException: Incompatible namespaceIDs in the logs of a datanode (/logs/hadoop-hadoop-datanode-.log) might be caused by bug HADOOP-1212. Here is a site which provides how to get around this bug,
http://www.michael-noll.com/wiki/Running_Hadoop_On_Ubuntu_Linux_(Multi-Node_Cluster)

The complete error message was,

 ... ERROR org.apache.hadoop.dfs.DataNode: java.io.IOException: Incompatible namespaceIDs in /usr/local/hadoop-datastore/hadoop-hadoop/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)