2、hadoop之HDFS的常用命令操作

1、基本语法

bin/hadoop fs 具体命令
或
bin/hdfs dfs 具体命令
（dfs是fs的实现类）

二者区别

• hadoop fs：可以作用于除hdfs外的其他文件系统，作用范围更广。通用的文件系统命令，针对任何系统，比如本地文件、HDFS文件、HFTP文件、S3文件系统等。

（曾经还有hadoop dfs：专门针对hdfs分布式文件系统，已经不推荐使用）

• hdfs dfs：专门针对hdfs分布式文件系统，相比于上面的命令更为推荐，并且当使用hadoop dfs时内部会被转为hdfs dfs命令。

2、常用命令操作

》启动hadoop集群

sbin/start-dfs.sh
sbin/start-yarn.sh
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（1）-help：可数出命令所需的参数

hadoop@hadoop101:/opt/module/hadoop-3.1.3/bin$ 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.  

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（2）-ls：显示目录信息

hadoop@hadoop101:/opt/module/hadoop-3.1.3/bin$ hadoop fs -ls /
Found 1 items
drwxr-xr-x   - hadoop supergroup          0 2020-02-29 00:11 /home
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（3）-mkdir：在HDFS上创建目录

hadoop@hadoop101:/opt/module/hadoop-3.1.3/bin$ hadoop fs -mkdir -p /home/hadoop/op_test
hadoop@hadoop101:/opt/module/hadoop-3.1.3/bin$ hadoop fs -ls /home/hadoop
Found 2 items
drwxr-xr-x   - hadoop supergroup          0 2020-02-29 00:14 /home/hadoop/input
drwxr-xr-x   - hadoop supergroup          0 2020-03-02 06:42 /home/hadoop/op_test
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（4）-moveFromLocal：从本地剪切粘贴到HDFS

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ touch op_test.txt
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ echo "hello,hdfs" >> op_test.txt
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -moveFromLocal ./op_test.txt /home/hadoop/op_test
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ ls
test.input
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（5）-appendToFile：追加一个文件到已经存在的文件末尾

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ touch op_append.txt
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ echo "append-hdfs" >> op_append.txt
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop -appendToFile op_append.txt /home/hadoop/op_test/op_test.txt
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（6）-cat：显示文件内容

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -cat /home/hadoop/op_test/op_test.txt
hello,hdfs
append-hdfs
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（7）-chgrp、-chmod、-chown：Linux文件系统中的用法一样，修改文件所述权限

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -chmod 666 /home/hadoop/op_test/op_test.txt
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -chown hadoop:hadoop /home/hadoop/op_test/op_test.txt
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（8）-copyFromLocal：从本地文件系统中拷贝文件到HDFS路径去

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ ls
op_append.txt  test.input
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -copyFromLocal test.input /home/hadoop/op_test
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（9）-copyToLocal：从HDFS拷贝到本地

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -copyToLocal /home/hadoop/op_test/op_test.txt ./
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ ls
op_append.txt  op_test.txt  test.input
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（10）-cp：从HDFS的一个路径拷贝到HDFS的另一个路径

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -cp /home/hadoop/op_append.txt /home/hadoop/op_test
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（11）-mv：在HDFS目录中移动文件

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -mv /home/hadoop/op_test/op_append.txt /home/hadoop
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（12）-get：等同于copyToLocal，从HDFS下载文件到本地

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -get /home/hadoop/op_append.txt ./
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ ls
op_append.txt  op_test.txt  test.input
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（13）-getmerge：从HDFS的目录下，将文件合并起来后下载

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -getmerge /home/hadoop/op_test/* ./common.txt

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ ls
common.txt  op_append.txt  op_test.txt  test.input

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ cat common.txt
append-hdfs
hello,hadoop!
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（14）-put：等同于copyFromLocal，从HDFS目录下拷贝文件到本地

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -put ./common.txt /home/hadoop/op_test/
2020-03-02 07:15:57,049 INFO sasl.SaslDataTransferClient: SASL encryption trust check: localHostTrusted = false, remoteHostTrusted = false
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -ls /home/hadoop/op_test
Found 3 items
-rw-r--r--   3 hadoop supergroup         26 2020-03-02 07:15 /home/hadoop/op_test/common.txt
-rw-r--r--   3 hadoop supergroup         12 2020-03-02 07:06 /home/hadoop/op_test/op_append.txt
-rw-r--r--   3 hadoop supergroup         14 2020-03-02 06:56 /home/hadoop/op_test/test.input
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（15）-tail：显示一个文件的末尾

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -tail 
home/hadoop/op_test/common.txt
append-hdfs
hello,hadoop!
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（16）-rm：删除文件或文件夹

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -rm /home/hadoop/*.txt
Deleted /home/hadoop/op_append.txt
Deleted /home/hadoop/op_test.txt
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（17）-rmdir：删除空目录

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -mkdir /test
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -rmdir /test
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（18）-du：统计文件夹的大小信息

-h：显示带MB及以上的可读形式

-s：得到文件夹下文件大小的总和

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -du /home/hadoop/op_test
26  78  /home/hadoop/op_test/common.txt
12  36  /home/hadoop/op_test/op_append.txt
14  42  /home/hadoop/op_test/test.input
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -du -h /home/hadoop/op_test
26  78  /home/hadoop/op_test/common.txt
12  36  /home/hadoop/op_test/op_append.txt
14  42  /home/hadoop/op_test/test.input
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -du -s /home/hadoop/op_test
52  156  /home/hadoop/op_test
hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -du -s -h /home/hadoop/op_test
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（19）-setrep：设置HDFS中文件的副本数量

hadoop@hadoop101:/opt/module/hadoop-3.1.3/testinput$ hadoop fs -setrep 2 /home/hadoop/op_test/common.txt
Replication 2 set: /home/hadoop/op_test/common.txt
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注：实际可存在的副本数受DataNode的数量限制，不可大于DataNode的数量。若设置的副本数大于DataNode的数量，只在NameNode中记录本次设置的数量，而实际的副本数量将自动被控制为与DataNode相同数量。