Hadoop 2.x 开始jar包拆分了，不单一个core包了。跑个WordCount得加这几个：$HADOOP_HOME/share/hadoop/common/hadoop-common-2.6.0.jar、$HADOOP_HOME/share/hadoop/mapreduce/hadoop-mapreduce-client-core-2.6.0.jar 和 $HADOOP_HOME/share/hadoop/common/lib/commons-cli-1.2.jar，缺一不可，搞错了直接报错，挺坑的~