hadoop ERROR: Attempting to operate on hdfs namenode as root ERROR: but there is no HDFS_NAMENODE_US

[root@master ~]# 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 [master]
ERROR: Attempting to operate on hdfs secondarynamenode as root
ERROR: but there is no HDFS_SECONDARYNAMENODE_USER defined. Aborting operation.
解决方法：

在Hadoop安装目录下找到sbin文件夹

在里面修改四个文件

对于start-dfs.sh和stop-dfs.sh文件，添加下列参数：

#!/usr/bin/env bash
HDFS_DATANODE_USER=root
HADOOP_SECURE_DN_USER=hdfs
HDFS_NAMENODE_USER=root
HDFS_SECONDARYNAMENODE_USER=root

对于start-yarn.sh和stop-yarn.sh文件，添加下列参数：

#!/usr/bin/env bash
YARN_RESOURCEMANAGER_USER=root
HADOOP_SECURE_DN_USER=yarn
YARN_NODEMANAGER_USER=root

重新开始start...就可以了。