HDFS API

• 常用命令

进入/home/hadoop-2.4.0/bin目录

列出根目录：hadoop fs -ls

创建目录：hadoop fs -mkdir /root

删除目录：hadoop fs -rmr /root

本地文件到HDFS：hadoop fs -put /home/test.txt /root/test.txt

HDFS到本地文件：hadoop fs -get /root/test.txt /home/test.txt

查看文件：hadoop fs -cat /root/test.txt

目录赋权限： hadoop fs -chmod 777 /root

 

• web管理页面

可以通过http://master:50070访问HDFS的web管理页面

 

• java API

读文件

String uri = "hdfs://master:9000/input/file01";
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(uri), conf);
		
InputStream in = fs.open(new Path(uri));
IOUtils.copyBytes(in, System.out, 4096, false);
IOUtils.closeStream(in);

写文件

		String dst = "hdfs://master:9000/input/file03";
		String src = "c://aa.txt";
		InputStream in = new BufferedInputStream(new FileInputStream(src));
		Configuration conf = new Configuration();
		FileSystem fs = FileSystem.get(URI.create(dst), conf);
		
		
		OutputStream out = fs.create(new Path(dst));
		IOUtils.copyBytes(in, out, 4096, true);
		IOUtils.closeStream(in);

删除文件

		String dst = "hdfs://master:9000/input/file03";
		Configuration conf = new Configuration();
		FileSystem fs = FileSystem.get(URI.create(dst), conf);
		
		fs.delete(new Path(dst), true);