Class org.apache.hadoop.hdfs.DistributedFileSystem not found

加载hadoop-hdfs-client-3.1.1.jar，可以从maven仓库下载，链接
https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-hdfs-client

hdfs ip:9000 failed on connection exception: java.net.ConnectException:Connection refused

在配置文件是使用了localhost 或 127.0.0.1，此时应该改为真实的ID

错误Name node is in safe mode的解决方法

hadoop dfsadmin -safemode leave

AccessControlException: Permission denied: user=luoyufeng, access=WRITE,

需要修改文件目录权限

hdfs dfs -chmod -R 777 需要修改权限的目录