How to Manage File Permissions in Linux (chmod & chown Explained)

One of the most important skills in Linux is understanding file permissions. Permissions control who can read, write, and execute files — and they are critical for security and system management.

In this guide, you will learn how Linux permissions work and how to use the chmod and chown commands step-by-step.

Understanding Linux File Permissions

Every file and directory in Linux has three types of permissions:

• Read (r) — View the contents
• Write (w) — Modify the file
• Execute (x) — Run the file as a program

These permissions are assigned to three groups:

• User (u) — The file owner
• Group (g) — Users in the same group
• Others (o) — Everyone else

Viewing Permissions

ls -l

Example output:

-rw-r--r-- 1 student student 220 file.txt

Breakdown:

• - = file type
• rw- = owner permissions
• r-- = group permissions
• r-- = others permissions

Using chmod (Change Permissions)

Symbolic Mode

chmod u+x file.sh

Adds execute permission for the user.

chmod g-w file.txt

Removes write permission from the group.

Numeric Mode

Permissions can also be set using numbers:

• 4 = Read
• 2 = Write
• 1 = Execute

Example:

chmod 755 script.sh

Breakdown:

• 7 (4+2+1) = full access
• 5 (4+1) = read + execute
• 5 (4+1) = read + execute

Using chown (Change Ownership)

sudo chown user file.txt

Changes file owner.

sudo chown user:group file.txt

Changes both owner and group.

Real Practice Example

touch test.sh
chmod 755 test.sh
ls -l test.sh

You should see executable permissions added.

Why Permissions Matter

• Prevent unauthorized access
• Protect system files
• Control application behavior
• Improve system security

Common Mistakes

• Using chmod 777 (dangerous — full access to everyone)
• Forgetting to use sudo when needed
• Misunderstanding numeric permissions

Final Thoughts

Mastering file permissions is a major step toward becoming a Linux professional.

Once you understand permissions, you will be able to manage servers, secure systems, and troubleshoot access issues with confidence.

👉 Practice chmod and chown in a live Linux lab now