【Hadoop|HDFS篇】HDFS的Shell操作

1. 基本语法

hadoop fs 具体命令或者hadoop dfs 具体命令。

两个是完全相同的。

2. 命令大全

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] [-d] [-t <thread count>] <localsrc> ... <dst>]
    [-copyToLocal [-f] [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]
    [-count [-q] [-h] [-v] [-t [<storage type>]] [-u] [-x] [-e] <path> ...]
    [-cp [-f] [-p | -p[topax]] [-d] <src> ... <dst>]
    [-createSnapshot <snapshotDir> [<snapshotName>]]
    [-deleteSnapshot <snapshotDir> <snapshotName>]
    [-df [-h] [<path> ...]]
    [-du [-s] [-h] [-v] [-x] <path> ...]
    [-expunge]
    [-find <path> ... <expression> ...]
    [-get [-f] [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]
    [-getfacl [-R] <path>]
    [-getfattr [-R] {-n name | -d} [-e en] <path>]
    [-getmerge [-nl] [-skip-empty-file] <src> <localdst>]
    [-head <file>]
    [-help [cmd ...]]
    [-ls [-C] [-d] [-h] [-q] [-R] [-t] [-S] [-r] [-u] [-e] [<path> ...]]
    [-mkdir [-p] <path> ...]
    [-moveFromLocal <localsrc> ... <dst>]
    [-moveToLocal <src> <localdst>]
    [-mv <src> ... <dst>]
    [-put [-f] [-p] [-l] [-d] <localsrc> ... <dst>]
    [-renameSnapshot <snapshotDir> <oldName> <newName>]
    [-rm [-f] [-r|-R] [-skipTrash] [-safely] <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] [-s <sleep interval>] <file>]
    [-test -[defsz] <path>]
    [-text [-ignoreCrc] <src> ...]
    [-touch [-a] [-m] [-t TIMESTAMP ] [-c] <path> ...]
    [-touchz <path> ...]
    [-truncate [-w] <length> <path> ...]
    [-usage [cmd ...]]

Generic options supported are:
-conf <configuration file>        specify an application configuration file
-D <property=value>               define a value for a given property
-fs <file:///|hdfs://namenode:port> specify default filesystem URL to use, overrides 'fs.defaultFS' property from configurations.
-jt <local|resourcemanager:port>  specify a ResourceManager
-files <file1,...>                specify a comma-separated list of files to be copied to the map reduce cluster
-libjars <jar1,...>               specify a comma-separated list of jar files to be included in the classpath
-archives <archive1,...>          specify a comma-separated list of archives to be unarchived on the compute machines

The general command line syntax is:
command [genericOptions] [commandOptions]

2.1 help命令

hadoop fs -help 命令

比如：

[hexuan@hadoop102 ~]$ hadoop fs -help ls
-ls [-C] [-d] [-h] [-q] [-R] [-t] [-S] [-r] [-u] [-e] [<path> ...] :
  List the contents that match the specified file pattern. If path is not
  specified, the contents of /user/<currentUser> will be listed. For a directory a
  list of its direct children is returned (unless -d option is specified).
  
  Directory entries are of the form:
      permissions - userId groupId sizeOfDirectory(in bytes)
  modificationDate(yyyy-MM-dd HH:mm) directoryName
  
  and file entries are of the form:
      permissions numberOfReplicas userId groupId sizeOfFile(in bytes)
  modificationDate(yyyy-MM-dd HH:mm) fileName
  
    -C  Display the paths of files and directories only.
    -d  Directories are listed as plain files.
    -h  Formats the sizes of files in a human-readable fashion
        rather than a number of bytes.
    -q  Print ? instead of non-printable characters.
    -R  Recursively list the contents of directories.
    -t  Sort files by modification time (most recent first).
    -S  Sort files by size.
    -r  Reverse the order of the sort.
    -u  Use time of last access instead of modification for
        display and sorting.
    -e  Display the erasure coding policy of files and directories.

2.2 上传

（1）-moveFromLocal ：从本地剪切黏贴到HDFS

[hexuan@hadoop102 ~]$ vim wuguo.txt
[hexuan@hadoop102 ~]$ hadoop fs -moveFromLocal wuguo.txt /sanguo/
2024-09-04 10:39:14,395 INFO sasl.SaslDataTransferClient: SASL encryption trust check: localHostTrusted = false, remoteHostTrusted = false

（2）-copyFromLocal：从本地文件系统拷贝文件到HDFS中。

hadoop fs -copyFromLocal wuguo.txt /sanguo/

（3）-put：等同于copyFromLocal，生产环境更习惯于用put。

hadoop fs -put wuguo.txt /sanguo/

（4）-appendToFile：追加一个文件到已经存在的文件末尾。

2.3 下载

（1）-copyToLocal：从HDFS拷贝到本地

（2）-get：等同于copyToLocal，生产环境中更常用get。

[hexuan@hadoop102 ~]$ hadoop fs -get /sanguo/wuguo.txt ./wuguo_copy.txt
2024-09-04 10:59:00,847 INFO sasl.SaslDataTransferClient: SASL encryption trust check: localHostTrusted = false, remoteHostTrusted = false

2.4 其他命令

（1）-ls：显示目录信息。

（2）-cat：显示文件内容。

（3）-chgrp，-chmod，-chown：与Linux系统中的用法一致，修改文件的权限。

（4）-mkdir：创建文件目录。

（5）-cp：从HDFS的一个路径复制到另一个路径。

（6）-mv：在HDFS中移动文件。

（7）-tail：显示一个文件的末尾1kb的数据。

（8）-rm：删除文件或文件夹。

（9）-rm -r：递归删除目录和目录里的内容。

（10）-du：统计文件夹的大小信息。

[hexuan@hadoop102 ~]$ hadoop fs -du /sanguo
40  120  /sanguo/jiangwei.txt._COPYING_
0   0    /sanguo/simayi.txt
12  36   /sanguo/wuguo.txt
[hexuan@hadoop102 ~]$ hadoop fs -du -s /sanguo
52  156  /sanguo

说明：

40， 12， 52表示的都是文件大小，120表示的是40*3个副本，/sanguo表示查看的目录。

添加选项-s显示文件夹整体的信息。

（11）-setrep：设置HDFS中文件的副本数量

[hexuan@hadoop102 ~]$ hadoop fs -setrep 10 /sanguo/wuguo.txt
Replication 10 set: /sanguo/wuguo.txt

这里设置的副本数只是记录在NameNode的元数据，是否真的会有这么多副本，还得看DataNode的数量。目前只有三台设备，所以最多也就三个副本，只有当节点数达到10台，副本数才能到10个。