HDFS常用命令

操作HDFS文件命令的两种格式：
hadoop fs -ls /
hdfs dfs -ls /
一般我们是使用第二个。
下面我们一起看一下 hdfs dfs的一些常见命令：
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hdfs dfs 回车

[hadoop@vm01 ~]$ hdfs dfs 
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] [-v] <path> ...]
        [-cp [-f] [-p | -p[topax]] <src> ... <dst>]
        [-createSnapshot <snapshotDir> [<snapshotName>]]
        [-deleteSnapshot <snapshotDir> <snapshotName>]
        [-df [-h] [<path> ...]]
        [-du [-s] [-h] <path> ...]
        [-expunge]
        [-find <path> ... <expression> ...]
        [-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 ...]]

Generic options supported are
-conf <configuration file>     specify an application configuration file
-D <property=value>            use value for given property
-fs <local|namenode:port>      specify a namenode
-jt <local|resourcemanager:port>    specify a ResourceManager
-files <comma separated list of files>    specify comma separated files to be copied to the map reduce cluster
-libjars <comma separated list of jars>    specify comma separated jar files to include in the classpath.
-archives <comma separated list of archives>    specify comma separated archives to be unarchived on the compute machines.

The general command line syntax is
bin/hadoop command [genericOptions] [commandOptions]

大部分我们一看就明白，其实基本跟linux基本命令是一样的，下面只列举几个特有的：

 [-copyFromLocal [-f] [-p] [-l] <localsrc> ... <dst>]
 [-copyToLocal [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]

 [-put [-f] [-p] [-l] <localsrc> ... <dst>]
 [-get [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]

这两组命令，通过后面的选项其实就已经知道，他们是一回事，分别是linux本地文件到hdfs文件系统的上传和下载
上传文件到hdfs

[hadoop@vm01 ~]$ hdfs dfs -copyFromLocal /home/hadoop/a.txt  /test/
[hadoop@vm01 ~]$ hdfs dfs -put /home/hadoop/a.txt  /test/

下载文件到linux本地

[hadoop@vm01 ~]$ hdfs dfs -copyToLocal /test/a.txt  /home/hadoop/
[hadoop@vm01 ~]$ hdfs dfs -get /test/a.txt  /home/hadoop/

查看文件系统状态

[hadoop@vm01 ~]$ hdfs dfsadmin -report
[hadoop@vm01 ~]$ hdfs fsck /

查看/tools目录或文件的信息

hdfs dfs -stat [format] /tools  
format参数：
            %b（文件大小）
            %o（Block大小）
            %n（文件名）
            %r（副本个数）
            %y（最后一次修改日期和时间）
            可以这样书写hadoop fs -stat %b%o%n < hdfs path >