我已经在网站上配置并安装了hadoop
http://www.srccodes.com/p/article/38/build-install-configure-run-apache-hadoop-2.2.0-microsoft-windows-os
当我使用命令格式化hadoop namenode时 alim@Hadoop~/hadoop-2.4.0/bin$ ./hdfs namenode -format or alim@Hadoop~/hadoop-2.4.0/bin$ ./hadoop namenode -format 它显示“noclassdeffounderror”异常
下面是运行“hadoopnamenode-format”命令时显示的异常 java.lang.NoClassDefFoundError: org/apache/hadoop/hdfs/server/namenode/NameNode Caused by: java.lang.ClassNotFoundException: org.apache.hadoop.hdfs.server.namenode.NameNode at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) Could not find the main class: org.apache.hadoop.hdfs.server.namenode.NameNode. Program will exit. Exception in thread "main" 一开始我认为hadoop类路径不是指向hadoop核心jar文件，而是在我运行命令时 alim@Hadoop~/hadoop-2.4.0/bin$ ./hadoop classpath 它显示了到库的正确路径，然后说明了noclassdeffounderror出错的原因
库的路径如下所示： /home/alim/hadoop-2.4.0/etc/hadoop:/home/alim/hadoop-2.4.0/share/hadoop/common/lib/:/home/alim/hadoop-2.4.0/share/hadoop/common/:/home/alim/hadoop-2.4.0/share/hadoop/hdfs:/home/alim/hadoop-2.4.0/share/hadoop/hdfs/lib/:/home/alim/hadoop-2.4.0/share/hadoop/hdfs/:/home/alim/hadoop-2.4.0/share/hadoop/yarn/lib/:/home/alim/hadoop-2.4.0/share/hadoop/yarn/:/home/alim/hadoop-2.4.0/share/hadoop/mapreduce/lib/:/home/alim/hadoop-2.4.0/share/hadoop/mapreduce/:C:\cygwin64\home\alim\hadoop-2.4.0/contrib/capacity-scheduler/*.jar 请帮助我是hadoop的初学者。。。。有什么想法吗