Tutorial

Linux Permissions Guide

Understanding chmod, chown, and the Linux permission model.

What Are Linux Permissions?

Every file and directory in Linux has three types of permissions: read (r), write (w), and execute (x). These are assigned to three categories: owner (u), group (g), and others (o).

Permission Numeric Values

Value	Permission	Symbol
7	Read + Write + Execute	rwx
6	Read + Write	rw-
5	Read + Execute	r-x
4	Read Only	r--
3	Write + Execute	-wx
2	Write Only	-w-
1	Execute Only	--x
0	No Permissions	---

Common chmod Examples

bash

chmod 755 script.sh     # rwxr-xr-x

bash

chmod 644 index.html    # rw-r--r--

bash

chmod 700 private.key   # rwx------

bash

chmod +x script.sh      # Add execute for all

bash

chmod -R 755 /var/www/  # Recursive on directory

chown — Change Ownership

Change which user and group owns a file.

bash

sudo chown tom:www-data file.txt
sudo chown -R www-data:www-data /var/www/html

Quick Quiz

What does chmod 644 do?