hadoop运行后，mapreduce报Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster_sqoop could not find or load main class org.apache-优快云博客

本文介绍了在Web端观察到YARN ResourceManager状态为failed的原因，发现是mapred-site.xml缺少配置。详细步骤包括添加mapreduce应用环境变量和classpath。参考链接提供了详细配置示例。

问题

今天Web端查看YARN 的ResourceManager发现State和FinalStatus都是failed
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原因

mapred-site.xml文件中少配置了一些东西

解决

进入hadoop的安装目录下的etc/hadoop/mapred-site.xml/文件
加入一下内容即可：

<!--用于集群跑mr任务-->
    <property>
        <name>mapreduce.application.classpath</name>
        <value>$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/*:$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/lib/*</value>
    </property>
    <property>
      <name>yarn.app.mapreduce.am.env</name>
      <value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value>
    </property>
    <property>
      <name>mapreduce.map.env</name>
      <value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value>
    </property>
    <property>
      <name>mapreduce.reduce.env</name>
      <value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value>
    </property>
<property>
    <name>yarn.application.classpath</name>
    <value>/opt/module/hadoop-3.1.3/etc/hadoop,
    /opt/module/hadoop-3.1.3/share/hadoop/common/lib/*,
    /opt/module/hadoop-3.1.3/share/hadoop/common/*,
    /opt/module/hadoop-3.1.3/share/hadoop/hdfs,
    /opt/module/hadoop-3.1.3/share/hadoop/hdfs/lib/*,
    /opt/module/hadoop-3.1.3/share/hadoop/hdfs/*,
    /opt/module/hadoop-3.1.3/share/hadoop/mapreduce/lib/*,
    /opt/module/hadoop-3.1.3/share/hadoop/mapreduce/*,
    /opt/module/hadoop-3.1.3/share/hadoop/yarn,
    /opt/module/hadoop-3.1.3/share/hadoop/yarn/lib/*,
    /opt/module/hadoop-3.1.3/share/hadoop/yarn/*
    </value>
  </property>

现在State和FinalStatus就成功了
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借鉴自博文：https://blog.youkuaiyun.com/muzhimuzhe/article/details/119838513