1application->container来管理。NameNode 的mapreduce log在userlogs。System.out 无法看到Mapper和Reducer的部分。
2log4j
3apache common LogFactory
4MultipleOutput ,program logputout
Hadoop:2.6:
mr-jobhistory-daemon.sh start historyserver jps JobHistoryServer
Tracking URL里面的History
yarn-site.xml里面配置aggregation为true: 看到每个Map和Reduce任务的Log
yarn-site.xml同步到所有的节点，重启集群
HDFS directory where the application logs are moved on application completion. Need to set appropriate permissions. Only applicable if log-aggregation is enabled. The default value is "/logs" or "/tmp/logs"
原文：http://www.cnblogs.com/yumanman/p/7577116.html