12. apache hadoop 伪分布式搭建-part2-HDFS简单命令

HDFS 简单用法

从官网查看dfs的基本用法
HDFS用法

操作HDFS 一共有三个命令：
hadoop fs： 使用面最广，可以操作任何文件系统。
hadoop dfs：只能操作HDFS文件系统相关（已Deprecated废弃）
hdfs dfs：只能操作HDFS文件系统相关

引用官网：

hadoop fs
FS relates to a generic file system which can point to any file systems like local, HDFS etc. So this can be used when you are dealing with different file systems such as Local FS, HFTP FS, S3 FS, and others

hadoop fs可以操作本地文件系统
hadoop fs -cat   file:///app/zpy/hadoop/etc/hadoop/kms-site.xml.   
hadoop fs可以操纵HDFS文件系统
hadoop fs -cat   hdfs://host1:port1/file1 hdfs://host2:port2/file2 

hadoop dfs
dfs is very specific to HDFS. would work for operation relates to HDFS. This has been deprecated and we should use hdfs dfs instead.
只能操作 HDFS 文件系统

hdfs dfs
same as 2nd i.e would work for all the operations related to HDFS and is the recommended command instead of hadoop dfs

[hadoop@bogon /]$ hadoop fs  -mkdir /dailiang 
[hadoop@bogon /]$ hadoop fs -ls /
Found 1 items
drwxr-xr-x   - hadoop supergroup          0 2017-08-31 15:12 /dailiang

[hadoop@bogon /]$ hdfs dfs -ls /
Found 1 items
drwxr-xr-x   - hadoop supergroup          0 2017-08-31 15:12 /dailiang

[hadoop@bogon /]$ hadoop fs -ls file:///app/zpy
Found 4 items
drwxr-xr-x   - hadoop hadoop        161 2017-08-31 14:52 file:///app/zpy/hadoop
-rw-r--r--   1 root   root    195515434 2015-10-31 05:04 file:///app/zpy/hadoop-2.6.2.tar.gz
drwxr-xr-x   - root   root           25 2017-07-27 12:24 file:///app/zpy/java
drwxr-xr-x   - root   root           20 2017-07-27 12:24 file:///app/zpy/ntp

上传本地文件至HDFS目录：

Usage: hdfs dfs -put  ... 
Copy single src, or multiple srcs from local file system to the destination file system.

hdfs dfs -put  /etc/fstab  /test/fstsb
/etc/fstab 是 本地文件
/test/fstab 是 HDFS 文件系统文件 

lsr 递归显示目录或者ls -R

hdfs dfs -lsr  /
lsr: DEPRECATED: Please use 'ls -R' instead.
drwxr-xr-x   - hadoop supergroup          0 2017-04-17 14:44 /test
-rw-r--r--   1 hadoop supergroup        805 2017-04-17 14:44 /test/fstsb

我们上面创建了一些文件，可去真正的数据目录看一下文件
/data/hadoop/hdfs/dn/current，发现里面很多东西，但是无法看懂
这里我们做个实验看一下

cd /data/hadoop/hdfs/dn/current/BP-47003996-127.0.0.1-1492394837095/current/finalized/subdir0/subdir0
[hadoop@localhost subdir0]$ cat blk_1073741825
# /etc/fstab
# Created by anaconda on Mon Nov  7 10:03:45 2016
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=78ab5608-8689-4ba6-90e5-dfb1c97895f9 /                       ext4    defaults        1 1
UUID=5629de06-8894-4df3-a822-6a4d8a846d79 /boot                   ext4    defaults        1 2
UUID=ad837aa0-307a-4957-a27e-bfe34809dcc9 swap                    swap    defaults        0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
我们是伪分布式，真正的hadoop集群的数据是会分片的

真正的hadoop集群应该这样看

hdfs dfs -cat /test/fstsb

查看版本：
[hadoop@localhost hadoop]$ hdfs version
Hadoop 2.6.2