Datanode process not running in Hadoop

I set up and configured a multi-node Hadoop cluster using this tutorial.

When I type in the start-all.sh command, it shows all the processes initializing properly as follows:

starting namenode, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-namenode-jawwadtest1.out
jawwadtest1: starting datanode, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-datanode-jawwadtest1.out
jawwadtest2: starting datanode, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-datanode-jawwadtest2.out
jawwadtest1: starting secondarynamenode, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-secondarynamenode-jawwadtest1.out
starting jobtracker, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-jobtracker-jawwadtest1.out
jawwadtest1: starting tasktracker, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-tasktracker-jawwadtest1.out
jawwadtest2: starting tasktracker, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-tasktracker-jawwadtest2.out

However, when I type the jps command, I get the following output:

31057 NameNode
4001 RunJar
6182 RunJar
31328 SecondaryNameNode
31411 JobTracker
32119 Jps
31560 TaskTracker

As you can see, there's no datanode process running. I tried configuring a single-node cluster but got the same problem. Would anyone have any idea what could be going wrong here? Are there any configuration files that are not mentioned in the tutorial or I may have looked over? I am new to Hadoop and am kinda lost and any help would be greatly appreciated.

EDIT: hadoop-root-datanode-jawwadtest1.log:

STARTUP_MSG:   args = []
STARTUP_MSG:   version = 1.0.3
STARTUP_MSG:   build = https://svn.apache.org/repos/asf/hadoop/common/branches/$
************************************************************/
2012-08-09 23:07:30,717 INFO org.apache.hadoop.metrics2.impl.MetricsConfig: loa$
2012-08-09 23:07:30,734 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapt$
2012-08-09 23:07:30,735 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl:$
2012-08-09 23:07:30,736 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl:$
2012-08-09 23:07:31,018 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapt$
2012-08-09 23:07:31,024 WARN org.apache.hadoop.metrics2.impl.MetricsSystemImpl:$
2012-08-09 23:07:32,366 INFO org.apache.hadoop.ipc.Client: Retrying connect to $
2012-08-09 23:07:37,949 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: $
        at org.apache.hadoop.hdfs.server.datanode.DataStorage.doTransition(Data$
        at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransition$
        at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNo$
        at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java$
        at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNod$
        at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode($
        at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataN$
        at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.$
        at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1$

2012-08-09 23:07:37,951 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: S$
/************************************************************
SHUTDOWN_MSG: Shutting down DataNode at jawwadtest1/198.101.220.90
************************************************************/

Solution

You need to do something like this:

bin/stop-all.sh (or stop-dfs.sh and stop-yarn.sh in the 2.x serie)
rm -Rf /app/tmp/hadoop-your-username/*
bin/hadoop namenode -format (or hdfs in the 2.x serie)

the solution was taken from: http://pages.cs.brandeis.edu/~cs147a/lab/hadoop-troubleshooting/. Basically it consists in restarting from scratch, so make sure you won't loose data by formating the hdfs.