hadoop-HDFS - 技术栈

1.HDFS简介

2.HDFS基本文件操作命令

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| 2.1 准备工作 1 ）启动单机Hadoop 2 ）-help：输出这个命令参数 hdfs dfs -help rm 3 ）创建/install文件夹 hdfs dfs -mkdir /sanguo |
| 2.2 上传 1 ）-moveFromLocal：从本地剪切粘贴到HDFS 2 ）-copyFromLocal：从本地文件系统中拷贝文件到HDFS路径去 3 ）-put：等同于copyFromLocal，生产环境更习惯用put 4 ）-appendToFile：追加一个文件到已经存在的文件末尾 |
| 2.3 HDFS 直接操作 1 ）-ls: 显示目录信息 hadoop fs -ls /sanguo 2 ）-cat：显示文件内容 hadoop fs -cat /install/shuguo.txt 3 ）-chgrp、-chmod、-chown：Linux文件系统中的用法一样，修改文件所属权限 hadoop fs -chmod 666 /sanguo/shuguo.txt hadoop fs -chown atguigu:atguigu /sanguo/shuguo.txt 4 ）-mkdir：创建路径 hadoop fs -mkdir /jinguo 5 ）-cp：从HDFS的一个路径拷贝到HDFS的另一个路径 hadoop fs -cp /sanguo/shuguo.txt /jinguo 6 ）-mv：在HDFS目录中移动文件 hadoop fs -mv /sanguo/wuguo.txt /jinguo hadoop fs -mv /sanguo/weiguo.txt /jinguo 7 ）-tail：显示一个文件的末尾1kb的数据 hadoop fs -tail /jinguo/shuguo.txt 8 ）-rm：删除文件或文件夹 hadoop fs -rm /sanguo/shuguo.txt 9 ）-rm -r：递归删除目录及目录里面内容 hadoop fs -rm -r /sanguo 10 ）-du统计文件夹的大小信息 hadoop fs -du -s -h /jinguo 27 81 /jinguo hadoop fs -du -h /jinguo 14 42 /jinguo/shuguo.txt 7 21 /jinguo/weiguo.txt 6 18 /jinguo/wuguo.tx 说明：27表示文件大小；81表示27*3个副本；/jinguo表示查看的目录 11 ）-setrep：设置HDFS中文件的副本数量（集群） hadoop fs -setrep 10 /jinguo/shuguo.txt 这里设置的副本数只是记录在NameNode的元数据中，是否真的会有这么多副本，还得看DataNode的数量。因为目前只有3台设备，最多也就3个副本，只有节点数的增加到10台时，副本数才能达到10。 |
| 2.4 进入资源管理器web页面：http://kb129:8088 |
| 2.5 查看历史服务器 （1）启动历史服务器：mapred --daemon start historyserver （2）进入历史服务器网页访问： http://kb129:19888 |

3. windows中hadoop环境搭建

4. Java实现HDFS文件读写

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| 4.1 创建maven工程，quickstart工程 （1）配置依赖 XML <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-common</artifactId> <version>${hadoop.version}</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-hdfs</artifactId> <version>${hadoop.version}</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-mapreduce-client-core</artifactId> <version>${hadoop.version}</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-mapreduce-client-common</artifactId> <version>${hadoop.version}</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-client</artifactId> <version>${hadoop.version}</version> </dependency> |
| 4.2 test 包中重写AppTest java package org.example; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.junit.After; import org.junit.Before; import org.junit.Test; import java.io.IOException; /** * Unit test for simple App. */ public class AppTest { //可操作hdfs文件系统的对象 FileSystem hdfs = null; @Before public void init() throws IOException { //构造一个配置参数对象，设置参数要访问的hdfs的url Configuration conf = new Configuration(); //指定使用hdfs访问 conf.set("fs.defaultFS","hdfs://kb129:9000"); System.setProperty("HADOOP_USER_NAME","root"); hdfs = FileSystem.get(conf); } //上传本地文件到hdfs @Test public void shouldAnswerWithTrue() throws IOException { Path localFilePath = new Path("C:\\Windows\\System32\\drivers\\etc\\services"); Path hdfsPath = new Path("/services.txt"); //上传 hdfs.copyFromLocalFile(localFilePath,hdfsPath); System.out.println("上传成功"); } //从hdfs下载文件到本地 @Test public void downloadFile() throws IOException { Path localFilePath = new Path("D:\\tttttmmmmmppppp"); Path hdfsPath = new Path("/services.txt"); //下载 hdfs.copyToLocalFile(hdfsPath,localFilePath); System.out.println("下载成功"); } @After public void close() throws IOException{ hdfs.close(); } } |