大数据学习（2）HDFS文件管理

 命令行管理HDFS

[root@server1 bin]# hadoop fs 
Usage: hadoop fs [generic options]
        [-appendToFile <localsrc> ... <dst>]
        [-cat [-ignoreCrc] <src> ...]
        [-checksum <src> ...]
        [-chgrp [-R] GROUP PATH...]
        [-chmod [-R] <MODE[,MODE]... | OCTALMODE> PATH...]
        [-chown [-R] [OWNER][:[GROUP]] PATH...]
        [-copyFromLocal [-f] [-p] [-l] <localsrc> ... <dst>]
        [-copyToLocal [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]
        [-count [-q] [-h] <path> ...]
        [-cp [-f] [-p | -p[topax]] <src> ... <dst>]
        [-createSnapshot <snapshotDir> [<snapshotName>]]
        [-deleteSnapshot <snapshotDir> <snapshotName>]
        [-df [-h] [<path> ...]]
        [-du [-s] [-h] <path> ...]
        [-expunge]
        [-get [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]
        [-getfacl [-R] <path>]
        [-getfattr [-R] {-n name | -d} [-e en] <path>]
        [-getmerge [-nl] <src> <localdst>]
        [-help [cmd ...]]
        [-ls [-d] [-h] [-R] [<path> ...]]
        [-mkdir [-p] <path> ...]
        [-moveFromLocal <localsrc> ... <dst>]
        [-moveToLocal <src> <localdst>]
        [-mv <src> ... <dst>]
        [-put [-f] [-p] [-l] <localsrc> ... <dst>]
        [-renameSnapshot <snapshotDir> <oldName> <newName>]
        [-rm [-f] [-r|-R] [-skipTrash] <src> ...]
        [-rmdir [--ignore-fail-on-non-empty] <dir> ...]
        [-setfacl [-R] [{-b|-k} {-m|-x <acl_spec>} <path>]|[--set <acl_spec> <path>]]
        [-setfattr {-n name [-v value] | -x name} <path>]
        [-setrep [-R] [-w] <rep> <path> ...]
        [-stat [format] <path> ...]
        [-tail [-f] <file>]
        [-test -[defsz] <path>]
        [-text [-ignoreCrc] <src> ...]
        [-touchz <path> ...]
        [-usage [cmd ...]]

JAVA操作HDFS

maven依赖：

　　<dependency>
        <groupId>jdk.tools</groupId>
        <artifactId>jdk.tools</artifactId>
        <version>1.6</version>
        <scope>system</scope>
        <systemPath>${JAVA_HOME}/lib/tools.jar</systemPath>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-hdfs</artifactId>
        <version>2.6.5</version>
    </dependency>
        
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-common</artifactId>
        <version>2.6.5</version>
    </dependency>

 上传&下载示例：

    public static void upload() throws Exception {
         Configuration conf = new Configuration();
         FileSystem fileSystem = FileSystem.get(new URI("hdfs://192.168.1.110:9000"),conf,"root");
         fileSystem.copyFromLocalFile(new Path("D:\test\2.txt"), new Path("/2.txt"));
         fileSystem.close();
    }
    public static void download() throws Exception {
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://192.168.1.110:9000");
        FileSystem fileSystem = FileSystem.get(conf);
        fileSystem.copyToLocalFile(false,new Path("/2.txt"),new Path("D:\test\2.download.txt"),true);
        fileSystem.close();
    }

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参考：

HDFS文件管理：http://hadoop.apache.org/docs/r2.6.5/hadoop-project-dist/hadoop-hdfs/HDFSCommands.html

API文档：https://hadoop.apache.org/docs/r2.8.2/api/index.html