Hadoop问题（一）--集群群起报waring以及无法启动:
1, ERROR: Attempting to operate on hdfs namenode as root
ERROR: but there is no HDFS_NAMENODE_USER defined. Aborting operation.
Starting datanodes
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hadoop1000: datanode is running as process 5514. Stop it first.
Starting secondary namenodes [hadoop1002]
ERROR: Attempting to operate on hdfs secondarynamenode as root
ERROR: but there is no HDFS_SECONDARYNAMENODE_USER defined. Aborting operation.
这个问题主要是因为：start-dfs.sh文件配置没有添加
HDFS_DATANODE_USER=root
HDFS_DATANODE_SECURE_USER=hdfs
HDFS_NAMENODE_USER=root
HDFS_SECONDARYNAMENODE_USER=root
这四句代码或者这四句有误导致的。
其中第二句话 如果为
HADOOP_SECURE_DN_USER=hdfs
就会报waring: : HADOOP_SECURE_DN_USER has been replaced by HDFS_DATANODE_SECURE_USER. Using value of HADOOP_SECURE_DN_USER.
所以要把这句话改为HDFS_DATANODE_SECURE_USER=hdfs
就好了！
