无法启动tasktracker，因为位于的java.lang.NullPointerException

我使用Hadoop 1.2.1创建了单节点群集，如下所示。但是，在尝试运行单节点群集时，我发现错误无法启动tasktracker，因为日志文件中显示了位于..的java.lang.NullPointerException。我已经阅读了，但是我无法获得针对我的案例的解决方案。请帮助我如何克服此问题？tasktracker.java源代码可能有什么问题？任何想法我都很感激。 Tasktracker日志文件：

2014-08-26 23:20:07,380 INFO org.apache.hadoop.mapred.TaskTracker: STARTUP_MSG: 
/************************************************************
STARTUP_MSG: Starting TaskTracker
STARTUP_MSG:   host = ubuntu/127.0.1.1
STARTUP_MSG:   args = []
STARTUP_MSG:   version = 1.2.2-SNAPSHOT
STARTUP_MSG:   build =  -r ; compiled by 'dere' on Tue Aug 12 03:45:50 PDT 2014
STARTUP_MSG:   java = 1.7.0_65
************************************************************/
2014-08-26 23:20:07,773 INFO org.apache.hadoop.metrics2.impl.MetricsConfig: loaded properties from hadoop-metrics2.properties
2014-08-26 23:20:07,861 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source MetricsSystem,sub=Stats registered.
2014-08-26 23:20:07,862 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Scheduled snapshot period at 10 second(s).
2014-08-26 23:20:07,862 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: TaskTracker metrics system started
2014-08-26 23:20:07,876 ERROR org.apache.hadoop.mapred.TaskTracker: Can not start task tracker because java.lang.NullPointerException
    at org.apache.hadoop.mapred.TaskTracker.<init>(TaskTracker.java:247)
    at org.apache.hadoop.mapred.TaskTracker.main(TaskTracker.java:3965)

2014-08-26 23:20:07,876 INFO org.apache.hadoop.mapred.TaskTracker: SHUTDOWN_MSG: 
/************************************************************
SHUTDOWN_MSG: Shutting down TaskTracker at ubuntu/127.0.1.1
************************************************************/

---

我们无法调试不可见代码。我应该添加哪些信息？我添加了我认为可能必要的信息。请立即帮助我。在我可以添加的任何时候告诉我要添加什么。请帮助我！

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

<configuration>
<property>
  <name>hadoop.tmp.dir</name>
  <value>/app/hadoop/tmp</value>
  <description>A base for other temporary directories.</description>
</property>

<property>
  <name>fs.default.name</name>
  <value>hdfs://localhost:54310</value>
  <description>The name of the default file system.  A URI whose
  scheme and authority determine the FileSystem implementation.  The
  uri's scheme determines the config property (fs.SCHEME.impl) naming
  the FileSystem implementation class.  The uri's authority is used to
  determine the host, port, etc. for a filesystem.</description>
</property>

</configuration>

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

<configuration>
<property>
  <name>dfs.replication</name>
  <value>1</value>
  <description>Default block replication.
  The actual number of replications can be specified when the file is created.
  The default is used if replication is not specified in create time.
  </description>
</property>

</configuration>

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

<configuration>
<property>
  <name>mapred.job.tracker</name>
  <value>localhost:54311</value>
  <description>The host and port that the MapReduce job tracker runs
  at.  If "local", then jobs are run in-process as a single map
  and reduce task.
  </description>
</property>

</configuration>

dere@ubuntu:~/Desktop/hadoop-1.2.1/bin$ jps
3165 JobTracker
3370 Jps
3086 SecondaryNameNode
2766 NameNode
2911 DataNode