1. Check Hadoop version on Ubuntu 18.04 or Find Hadoop Installed Version

Syntax:

hadoop version

OR

hdfs version

Output

Hadoop 3.1.1
Source code repository https://github.com/apache/hadoop -r 2b9a8c1d3a2caf1e733d57f346af3ff0d5ba529c
Compiled by leftnoteasy on 2018-08-02T04:26Z
Compiled with protoc 2.5.0
From source with checksum f76ac55e5b5ff0382a9f7df36a3ca5a0
This command was run using /usr/local/hadoop/share/hadoop/common/hadoop-common-3.1.1.jar

It’s clearly showing hadoop version 3.1.1

2. List Directories in HDFS on Hadoop 3.11 – Ubuntu 18.04

Syntax:

hadoop fs -ls /

Output

Found 1 items
drwxr-xr-x - hduser supergroup 0 2018-09-16 01:51 /hadoop
hduser@sachin-Inspiron-15-3567:/usr/local/hadoop/etc/hadoop$

hadoop directory is listing

This Hadoop fs command behaves like -ls, but recursively displays entries in all sub directories of a path

hdfs dfs -ls -R /

Output

drwxr-xr-x - hduser supergroup 0 2018-09-16 01:51 /hadoop 
drwxr-xr-x - hduser supergroup 0 2018-09-17 23:53 /sample 
drwxr-xr-x - hduser supergroup 0 2018-09-17 23:53 /sample/a

You can list directory by using browser GUI

click url http://localhost:9870/explorer.html#/

Click on Utilities -> Browse the file system

3. Create directory on Hadoop file system on Hadoop 3.1.1 Ubuntu 18.04

Syntax :

hdfs dfs -mkdir /<directory location with name>

Ex: Create new directory sample on hdfs

hdfs dfs -mkdir /sample
hadoop fs -ls /
Found 2 items
drwxr-xr-x - hduser supergroup 0 2018-09-16 01:51 /hadoop
drwxr-xr-x - hduser supergroup 0 2018-09-17 23:46 /sample

Above command creates sample directory at root “/” location.

4 .put

put command copies the file or directory from the local file system to the destination of hadoop file system dfs.

Syntax:

put <localSrc> <dest>

Ex: Insert text file a.txt to hadoop dfs directory /sample/

hdfs dfs -put a.txt /sample/

list inserted file on hadoop dfs

hadoop fs -ls /sample/
Found 2 items
drwxr-xr-x   - hduser supergroup          0 2018-09-17 23:53 /sample/a
-rw-r--r--   1 hduser supergroup         11 2018-09-18 00:55 /sample/a.txt

Read file on hdfs using cat

hdfs dfs -cat /sample/a.txt
hi sachin