Hadoop Commands

Most commonly Used Hadoop Commands With Examples

In this tutorial, we are going to study the most commonly used commands in Hadoop. These commands help in performing several HDFS file operations. These comprise copying a file, moving a file, showing the contents of the file, creating directories, etc. So let us begin with an introduction and then we will see different commands in Hadoop with examples.

Hadoop Commands List

Hadoop Commands

Hadoop stores petabytes of data using HDFS. HDFS is a distributed file system that stores structured to unstructured data. It provides redundant storage for files having a humongous size. There are several commands to perform different file operations. Let us take a look at some of the important Hadoop commands.



List of Hadoop Commands

1. version

Command Name: version

Command Usage: version

 Example:

  1. hadoop version

Version Command

Description: Version command Shows the version of Hadoop installed.

2. mkdir

Command Name: mkdir

Command Usage: mkdir <path>

Example:

  1. hdfs dfs -mkdir /ram/mrv1

mkdir command

Description: This command takes the <path> as an argument and creates the directory.

3. Is

Command Name: ls

Command Usage: ls <path>

Example:

  1. hdfs dfs -ls /user

Hadoop ls command

Description: This command displays the contents of the directory specified by <path>. It displays the name, permissions, owner, size, and modification date of each entry.

Second Example:

  1. hdfs dfs -ls -R /user

Description: This command works like ls but displays entries in all the subdirectories recursively.

4. put

Command Name: put

Command Usage: put <localsrc> <dest>

Example:

  1. hdfs dfs -put /home/sample.txt /user/dir1

Hadoop put Command

Description: This command copies the file in the local filesystem to the file in DFS.

5. copyFrom Local

Command Name: copyFrom Local

Command Usage: copyFrom Local <localsrc> <dest>

Example:

  1. hdfs dfs -copyFromLocal /home/sample /user/dir1

Hadoop copyFromLocal Command

Description: This command is the same as put command. But the source should refer to local files.

6. get

Command Name: get

Command Usage: get <src> <localdest>

Example:

  1. hdfs dfs -get /user/dir1 /home

Description: This Hadoop shell command copies the file in HDFS identified by <src> to file in local file system identified by <localdest>

Second Example:

  1. hdfs dfs -getmerge /user/dir1/sample.txt /user/dataflair/dir2/sample2.txt /home/sample1.txt

Description: This command retrieves all files in the source path entered by the user in HDFS and merges them into one single file created in the local file system identified by the local destination.

Third Example:

  1. hadoop fs –getfacl /user/dir1

Fourth Example:

  1. hadoop fs –getfacl -R /user/dir1

Description: This Hadoop command shows the Access Control Lists (ACLs) of files and directories. This command is used to display default ACL if the directory contains the same.

Options : -R: It recursively displays a list of all the ACLs of all files and directories.

 Fifth Example:

  1. hadoop fs –getfattr –d /user/dir1

Description: This HDFS command displays if there are any extended attribute names and values for the specified file or directory.

Options:-R: It shows the attributes for all files and directories recursively. -n name: It displays the named extended attribute value. -d: It displays all the extended attribute values associated with the pathname. -e encoding: Encodes values after extracting them. The acceptable coded forms that are “text”, “hex”, and “base64”. The values which are encoded as text strings get enclosed with double quotes (” “). It uses prefix 0x for hexadecimal conversion. And 0s for all the values which get coded as base64.

7. copyToLocal

Command Name: copyToLocal

Command Usage: copyToLocal <src> <localdest>

Example:

  1. hdfs dfs -copyToLocal /user/dir1 /home

Hadoop copyToLocal Command

Description: It is similar to get command. Only the difference is that in this the destination of the copied file should refer to a local file.

8. cat

Command Name: cat

Command Usage: cat <file-name>

Example:

  1. hdfs dfs -cat /user/cloudera/dezyre1/sample1.txt

Hadoop cat Command

Description: This HDFS  command displays the contents of the file on the console or stdout.

9. mv

Command Name: mv

Command Usage: mv <src> <dest>

Example:

  1. hdfs dfs -mv /user/dir1/sample.txt /user/dir2

Hadoop mv command

Description: This shell command moves the file from the specified source to the destination within HDFS. 

10. cp

Command Name: cp

Command Usage: cp <src> <dest>

Example:

  1. hdfs dfs -cp /user/dir2/sample1.txt /user/dir1

Hadoop cp Command

Description: This shell command copies the file or directory from the given source to the destination within HDFS.


Summary

There are several commands in “$HADOOP_HOME/bin/hadoop fs” other than what we have learned in this tutorial. What we have covered are the most commonly used basic commands to get started. If you are fixed somewhere then type the following:

  1. $HADOOP_HOME/bin/hadoop fs -help command-name

This will show a short usage summary of the command specified.