Linux File Permissions Explained (chmod, chown Guide)

Understanding file permissions is one of the most important skills in Linux. It controls who can read, write, and execute files on your system.

What Are File Permissions?

Every file and directory in Linux has permissions assigned to it. These permissions determine who can access or modify the file.

There are three types of users:

• Owner – The person who created the file
• Group – Users who share access
• Others – Everyone else

Permission Types

• r (read) – View contents
• w (write) – Modify contents
• x (execute) – Run the file

Viewing Permissions

ls -l

Example output:

-rwxr-xr-- 1 user user file.txt

Breakdown:

• Owner: rwx (read, write, execute)
• Group: r-x (read, execute)
• Others: r-- (read only)

Using chmod (Change Permissions)

chmod allows you to change file permissions.

chmod 755 script.sh

Meaning:

• 7 = read + write + execute
• 5 = read + execute
• 5 = read + execute

You can also use symbolic mode:

chmod u+x script.sh

This adds execute permission for the owner.

Using chown (Change Ownership)

chown changes the owner of a file.

chown user:group file.txt

This assigns the file to a new user and group.

Why Permissions Matter

• Prevent unauthorized access
• Protect system files
• Ensure proper application behavior

Common Mistakes

• Using chmod 777 (unsafe)
• Giving too many permissions
• Not understanding ownership

Best Practice

Always use the minimum permissions necessary for a task.

Practice in a Real Environment

The best way to learn permissions is by trying them yourself.

👉 Practice file permissions in a live Linux lab now

Final Thoughts

File permissions are a core part of Linux security. Mastering them will make you a more confident and capable Linux user.