1、master，slave都需要修改start-dfs.sh，stop-dfs.sh，start-yarn.sh，stop-yarn.sh四个文件
2、如果你的Hadoop是另外启用其它用户来启动，记得将root改为对应用户
HDFS格式化后启动dfs出现以下错误：
[root@master sbin]# ./start-dfs.sh
Starting namenodes on [master]
ERROR: Attempting to operate on hdfs namenode as root
ERROR: but there is no HDFS_NAMENODE_USER defined. Aborting operation.
Starting datanodes
ERROR: Attempting to operate on hdfs datanode as root
ERROR: but there is no HDFS_DATANODE_USER defined. Aborting operation.
Starting secondary namenodes [slave1]
ERROR: Attempting to operate on hdfs secondarynamenode as root
ERROR: but there is no HDFS_SECONDARYNAMENODE_USER defined. Aborting operation.
在/hadoop/sbin路径下： 将start-dfs.sh，stop-dfs.sh两个文件顶部添加以下参数
#!/usr/bin/env bash
HDFS_DATANODE_USER=root
HADOOP_SECURE_DN_USER=hdfs
HDFS_NAMENODE_USER=root
HDFS_SECONDARYNAMENODE_USER=root
还有，start-yarn.sh，stop-yarn.sh顶部也需添加以下：
#!/usr/bin/env bash
YARN_RESOURCEMANAGER_USER=root
HADOOP_SECURE_DN_USER=yarn
YARN_NODEMANAGER_USER=root
# Licensed to the Apache Software Foundation (ASF) under one or more
修改后重启 ./start-dfs.sh，成功！
参考：