Hadoop（二）：HDFS

发表于 2022-05-09 分类于 Big Data

本文字数： 6k 阅读时长 ≈ 5 分钟

本文为学习笔记，对应视频教程来自尚硅谷大数据Hadoop 3.x

HDFS概述

HDFS产出背景及定义

HDFS优缺点

HDFS组成架构

HDFS文件块大小（面试重点）

HDFS的Shell操作

基本语法

[eitan@hadoop102 ~]$ hadoop fs
Usage: hadoop fs [generic options]
	[-appendToFile <localsrc> ... <dst>]
	[-cat [-ignoreCrc] <src> ...]
	[-checksum [-v] <src> ...]
	[-chgrp [-R] GROUP PATH...]
	[-chmod [-R] <MODE[,MODE]... | OCTALMODE> PATH...]
	[-chown [-R] [OWNER][:[GROUP]] PATH...]
	[-concat <target path> <src path> <src path> ...]
	[-copyFromLocal [-f] [-p] [-l] [-d] [-t <thread count>] [-q <thread pool queue size>] <localsrc> ... <dst>]
	[-copyToLocal [-f] [-p] [-crc] [-ignoreCrc] [-t <thread count>] [-q <thread pool queue size>] <src> ... <localdst>]
	[-count [-q] [-h] [-v] [-t [<storage type>]] [-u] [-x] [-e] [-s] <path> ...]
	[-cp [-f] [-p | -p[topax]] [-d] [-t <thread count>] [-q <thread pool queue size>] <src> ... <dst>]
	[-createSnapshot <snapshotDir> [<snapshotName>]]
	[-deleteSnapshot <snapshotDir> <snapshotName>]
	[-df [-h] [<path> ...]]
	[-du [-s] [-h] [-v] [-x] <path> ...]
	[-expunge [-immediate] [-fs <path>]]
	[-find <path> ... <expression> ...]
	[-get [-f] [-p] [-crc] [-ignoreCrc] [-t <thread count>] [-q <thread pool queue size>] <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 [-f] [-p] [-l] [-d] <localsrc> ... <dst>]
	[-moveToLocal <src> <localdst>]
	[-mv <src> ... <dst>]
	[-put [-f] [-p] [-l] [-d] [-t <thread count>] [-q <thread pool queue size>] <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 -[defswrz] <path>]
	[-text [-ignoreCrc] <src> ...]
	[-touch [-a] [-m] [-t TIMESTAMP (yyyyMMdd:HHmmss) ] [-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]

常用命令实操

准备工作

启动 Hadoop 集群

-help：输出这个命令参数

[eitan@hadoop102 ~]$ hadoop fs -help rm
-rm [-f] [-r|-R] [-skipTrash] [-safely] <src> ... :
  Delete all files that match the specified file pattern. Equivalent to the Unix
  command "rm <src>"
                                                                                 
  -f          If the file does not exist, do not display a diagnostic message or 
              modify the exit status to reflect an error.                        
  -[rR]       Recursively deletes directories.                                   
  -skipTrash  option bypasses trash, if enabled, and immediately deletes <src>.  
  -safely     option requires safety confirmation, if enabled, requires          
              confirmation before deleting large directory with more than        
              <hadoop.shell.delete.limit.num.files> files. Delay is expected when
              walking over large directory recursively to count the number of    
              files to be deleted before the confirmation.

创建/sanguo文件夹

1	[eitan@hadoop102 ~]$ hadoop fs -mkdir /sanguo

上传

-moveFromLocal：从本地剪切粘贴到HDFS

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[eitan@hadoop102 ~]$ echo shuguo >> shuguo.txt

[eitan@hadoop102 ~]$ hadoop fs -moveFromLocal shuguo.txt /sanguo

-copyFromLocal：从本地文件系统中拷贝文件到HDFS路径去

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[eitan@hadoop102 ~]$ echo weiguo >> ./documents/txt/weiguo.txt

[eitan@hadoop102 ~]$ hadoop fs -copyFromLocal ./documents/txt/weiguo.txt /sanguo

-put：等同于copyFromLocal，生产环境更习惯用put

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[eitan@hadoop102 ~]$ echo wuguo >> ./documents/txt/wuguo.txt

[eitan@hadoop102 ~]$ hadoop fs -put ./documents/txt/wuguo.txt /sanguo

-appendToFile：追加一个文件到已经存在的文件末尾

1	[eitan@hadoop102 ~]$ hadoop fs -appendToFile ./documents/txt/liubei.txt /sanguo/shuguo.txt

下载

-copyToLocal/-get：从HDFS拷贝到本地，生产环境更习惯用get

1	[eitan@hadoop102 ~]$ hadoop fs -copyToLocal/-get /sanguo/shuguo.txt ./documents/txt/

HDFS直接操作

-ls: 显示目录信息

[eitan@hadoop102 ~]$ hadoop fs -ls /sanguo
Found 3 items
-rw-r--r--   3 eitan supergroup         14 2022-05-09 19:42 /sanguo/shuguo.txt
-rw-r--r--   3 eitan supergroup          7 2022-05-09 19:35 /sanguo/weiguo.txt
-rw-r--r--   3 eitan supergroup          6 2022-05-09 19:37 /sanguo/wuguo.txt

-cat：显示文件内容

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[eitan@hadoop102 ~]$ hadoop fs -cat /sanguo/shuguo.txt
shuguo
liubei

-chgrp、-chmod、-chown：Linux文件系统中的用法一样，修改文件所属权限

1 2	[eitan@hadoop102 ~]$ hadoop fs -chmod 666 /sanguo/shuguo.txt [eitan@hadoop102 ~]$ hadoop fs -chown eitan:eitan /sanguo/shuguo.txt

-mkdir：创建路径

1	[eitan@hadoop102 ~]$ hadoop fs -mkdir /jinguo

-cp：从HDFS的一个路径拷贝到HDFS的另一个路径

1	[eitan@hadoop102 ~]$ hadoop fs -cp /sanguo/shuguo.txt /jinguo

-mv：在HDFS目录中移动文件

1 2	[eitan@hadoop102 ~]$ hadoop fs -mv /sanguo/wuguo.txt /jinguo [eitan@hadoop102 ~]$ hadoop fs -mv /sanguo/weiguo.txt /jinguo

-tail：显示一个文件的末尾1kb的数据

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[eitan@hadoop102 ~]$ hadoop fs -tail /jinguo/shuguo.txt
shuguo
liubei

-rm：删除文件或文件夹

1 2	[eitan@hadoop102 ~]$ hadoop fs -rm /sanguo/shuguo.txt Deleted /sanguo/shuguo.txt

-rm -r：递归删除目录及目录里面内容
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[eitan@hadoop102 ~]$ hadoop fs -rm -r /sanguo

-du统计文件夹的大小信息

[eitan@hadoop102 ~]$ hadoop fs -du /jinguo
14  42  /jinguo/shuguo.txt
7   21  /jinguo/weiguo.txt
6   18  /jinguo/wuguo.txt

[eitan@hadoop102 ~]$ hadoop fs -du -s /jinguo
27  179  /jinguo

-setrep：设置HDFS中文件的副本数量
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[eitan@hadoop102 ~]$ hadoop fs -setrep 10 /jinguo/shuguo.txt
Replication 10 set: /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。

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