在集群上运行jar程序的时候，出现以下这个错误信息：
Container exited with a non-zero exit code 1. Error file: prelaunch.err.
Last 4096 bytes of prelaunch.err :
Last 4096 bytes of stderr :
Error: Could not find or load main class org.apache.hadoop.mapred.YarnChild
解决方法
1.打开配置文件yarn-site.xml
2.添加以下配置信息：
yarn.application.classpath
/opt/module/hadoop-3.3.1/etc/hadoop:/opt/module/hadoop-3.3.1/share/hadoop/common/lib/:/opt/module/hadoop-3.3.1/share/hadoop/common/:/opt/module/hadoop-3.3.1/share/hadoop/hdfs:/opt/module/hadoop-3.3.1/share/hadoop/hdfs/lib/:/opt/module/hadoop-3.3.1/share/hadoop/hdfs/:/opt/module/hadoop-3.3.1/share/hadoop/mapreduce/:/opt/module/hadoop-3.3.1/share/hadoop/yarn:/opt/module/hadoop-3.3.1/share/hadoop/yarn/lib/:/opt/module/hadoop-3.3.1/share/hadoop/yarn/*
3.执行source /etc/profile
4.如果生效了，就不用再重启，反之，重启一下系统。
