我在fedora上执行任何m/r2作业时都会遇到此异常。hadoop2.7.3和2.8.0有相同的问题。包括Hive。

[hadoop@master hadoop]$ yarn classpath
/opt/hadoop/hadoop-2.7.3/conf
/opt/hadoop/hadoop-2.7.3/conf
/opt/hadoop/hadoop-2.7.3/conf:/opt/hadoop/hadoop/share/hadoop/common/lib/*
/opt/hadoop/hadoop/share/hadoop/common/*
/opt/hadoop/hadoop/share/hadoop/hdfs
/opt/hadoop/hadoop/share/hadoop/hdfs/lib/*
/opt/hadoop/hadoop/share/hadoop/hdfs/*
/opt/hadoop/hadoop/share/hadoop/yarn/lib/*
/opt/hadoop/hadoop/share/hadoop/yarn/*
/opt/hadoop/hadoop/share/hadoop/mapreduce/share/hadoop/mapreduce/*
/opt/hadoop/hadoop/contrib/capacity-scheduler/*.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-app-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-common-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-core-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-hs-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-hs-plugins-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-2.7.3-tests.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-shuffle-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.3.jar
/opt/hadoop/hadoop/share/hadoop/yarn/*
/opt/hadoop/hadoop/share/hadoop/yarn/lib/*

mapred-site.xml文件

<configuration>

<property>
    <name>mapreduce.framework.name</name>
    <value>yarn</value>
</property>

<property> 
    <name>mapreduce.application.classpath</name>
    <value>$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/*,$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/lib/*</value>
</property>

</configuration>

和yarn-site.xml

<configuration>

<property>
    <name>yarn.nodemanager.aux-services</name>
    <value>mapreduce_shuffle</value>
</property>

<property>
    <name>yarn.application.classpath</name>
    <value>$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/*,$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/lib/*</value>
</property>

</configuration>

最后但并非最不重要的一点，环境设置：

export HADOOP_HOME=/opt/hadoop/hadoop
export HADOOP_COMMON_HOME=$HADOOP_HOME
export HADOOP_HDFS_HOME=$HADOOP_HOME
export HADOOP_MAPRED_HOME=$HADOOP_HOME
export HADOOP_YARN_HOME=$HADOOP_HOME
export HADOOP_OPTS="-Djava.library.path=$HADOOP_HOME/lib/native"
export HADOOP_COMMON_LIB_NATIVE_DIR=$HADOOP_HOME/lib/native

我很肯定我遗漏了一些明显的东西。我已经设置了多次，但一定有什么东西关闭了。
缺少的类实际上是类路径中jar的一部分。/opt/hadoop/hadoop文件夹由用户hadoop拥有，并具有所需的所有访问权限。