Linux Permissions - Files and Directories

11 June 2022 2-minute read

This document is incomplete, it’s being actively worked on by Patrick.

File and Directory - Ownership

chown command (user and groups).
chgrp command (groups).

File and Directory - Read/Write/Execute Permissions

The permissions are handled by the “chmod” command.

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chmod <permission> <filename/directory name>
chmod 777 filename
chmod 777 directory_name

Permissions Calculator Table

	Read (r)	Write (w)	Execute (x)
Owner	400	200	100
Group	40	20	10
Public	4	2	1

To create permissions, you add up the values above.

Example

Example 1: If you want to give a file only read permission for every level, you will add 400+40+4. This will create 444 as the permissions set (r–r–r–).

Example

Example 2: If you want to give read and write access to the owner, and the group, but only read access to public you would add up the values 400+200+100+40+20+10+4. This will create a 774 as the permissions set (rwxrwxr–).

Example

Example 3: If you want to give the owner full access, then everyone else no access you will use 7 for the owner, 0 for the group, and 0 for the public. This will create a 700 as the permission set (rwx——).

File and Directory Permissions - Over Explained for Nerds

Note

This is stuff that you don’t need to know to manage file permissions, but you might want to know.

Linux uses 3 bits of data to set the permission of a file or directory, which give you the ability to set the octal (base-8 number) with 8 numbers between 0 and 7. The Octal Representation table below explains how that works.

Octal Representation

Octal Value (0-7)	Binary Value	Visual Permissions	Description of Permissions
0	000	- - -	No Permissions
1	001	- - x	Only Execute
2	010	- w -	Only Write
3	011	- w x	Write and Execute
4	100	r - -	Only Read
5	101	r - x	Read and Execute
6	110	r w -	Read and Write
7	111	r w x	Read, Write, and Execute