常见的问题
start-dfs.sh和stop-dfs.sh启动停止问题
HDFS_DATANODE_USER=root
HADOOP_SECURE_DN_USER=hdfs
HDFS_NAMENODE_USER=root
HDFS_SECONDARYNAMENODE_USER=root
start-yarn.sh 和stop- yarn.sh启动停止问题
RN_RESOURCEMANAGER_USER=root
HADOOP_SECURE_DN_USER=yarn
YARN_NODEMANAGER_USER=root
YARN_RESOURCEMANAGER_USER=root
mapreduce启动不起来的问题: yarn-site.xml 配置这个: value值的获取: hadoop classpath
<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>
mapreduce让检查配置问题:
Please check whether your etc/hadoop/mapred-site.xml contains the below configuration:

解决方案: 路径进行更改为真实的路径 或者 忘记配置了上面的配置
注: 有时候 ${HADOOP_HOME}不管用
Hadoop启动停止及MapReduce常见问题
博客主要介绍了Hadoop相关的常见问题,包括start-dfs.sh和stop-dfs.sh、start-yarn.sh和stop-yarn.sh的启动停止问题,以及mapreduce启动不起来的问题。对于mapreduce问题,需检查配置,可将路径改为真实路径或补充缺失配置,且有时${HADOOP_HOME}会失效。
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