TaskTracker failed to start: NoClassDefFoundError: Configured.

[Jane Chen]

Hi,

I was trying to start up a single-node Hadoop cluster using 0.20.2.  

The namenode, datanode and jobtracker all started fine.  The task tracker 
failed with the following error:

2011-03-16 11:39:47,479 INFO org.apache.hadoop.mapred.TaskTracker: Starting 
thread: Map-events fetcher for all reduce tasks on 
tracker_localhost:localhost/127.0.0.1:58447
2011-03-16 11:39:47,480 ERROR org.apache.hadoop.mapred.TaskTracker: Can not 
start task tracker because java.lang.NoClassDefFoundError: Configured
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
        at 
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
        at 
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)

The HADOOP_CLASSPATH is set in hadoop-env.sh.  The classpath includes 
hadoop-0.20.2-core.jar, which contains Configured.  Any clues?

Thanks,
Jane