一、详细报错信息

[root@hadoop101 hadoop-3.1.3]# sbin/start-dfs.sh
Starting namenodes on [hadoop101]
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 [hadoop103]
ERROR: Attempting to operate on hdfs secondarynamenode as root
ERROR: but there is no HDFS_SECONDARYNAMENODE_USER defined. Aborting operation.

二、错误原因

Hadoop中没有默认root的用户，需要手动添加

三、解决

vim start-dfs.sh
添加：
	HDFS_DATANODE_USER=root
	HADOOP_SECURE_DN_USER=hdfs
	HDFS_NAMENODE_USER=root
	HDFS_SECONDARYNAMENODE_USER=root

vim stop-dfs.sh
添加：
	HDFS_DATANODE_USER=root
	HADOOP_SECURE_DN_USER=hdfs
	HDFS_NAMENODE_USER=root
	HDFS_SECONDARYNAMENODE_USER=root

vim start-yarn.sh
添加：
	YARN_RESOURCEMANAGER_USER=root
	HADOOP_SECURE_DN_USER=yarn
	YARN_NODEMANAGER_USER=root

vim stop-yarn.sh
添加：
	YARN_RESOURCEMANAGER_USER=root
	HADOOP_SECURE_DN_USER=yarn
	YARN_NODEMANAGER_USER=root

vim  /etc/selinux/config 
修改：
	SELINUX=enforcing 改为 SELINUX=disabled