Understanding Linux File Permissions (Simplified Guide)

Managing file permissions is a core part of Linux administration.
Every file and directory in Linux has permissions that determine who can read, write, or execute it.

🧱 The Basics

Before we look at the ls -l command, here’s a quick visual overview of how Linux file permissions work 👇

Linux File Permissions — how read, write, and execute bits map to owner, group, and others.

Each file or directory in Linux has a 10-character permission string shown when you run ls -l:

-rwxr-xr-x  1 user group  1234 Oct 23 10:00 file.sh

Let’s decode it step by step 👇

👤 Owner, Group, and Others

Linux permissions are divided into three sections:

So this line:

-rwxr-xr-x

means:

• Owner: read, write, execute
• Group: read, execute
• Others: read, execute

🔢 Numeric Permissions Explained

Permissions can also be represented numerically using the following values:

To calculate the numeric value:

• rwx = 4 + 2 + 1 = 7
• r-x = 4 + 0 + 1 = 5
• rw- = 4 + 2 + 0 = 6

Hence, 755 equals rwxr-xr-x.

Formula breakdown:

Owner: 7 (rwx)
Group: 5 (r-x)
Others: 5 (r-x)

⚙️ Common Permission Modes

Here are the most commonly used permission settings:

🧰 Using chmod

You can change permissions with the chmod command:

chmod 755 file.sh    # rwxr-xr-x
chmod u+x script.sh  # add execute permission for the user
ls -l file.sh        # view detailed permissions

If the first character is d, it’s a directory — for example:

drwxr-xr-x

That means it’s a directory, and the x bit allows users to enter it (cd directory).

🧠 Quick Tips

• x on a file → allows running it.
• x on a directory → allows entering it.
• Execute on directories controls traversal, not execution.

💡 Try It Yourself (Hands-On)

Let’s test this in your terminal:

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

You should see:

-rwxr-xr-x

✅ That means you (the owner) can read, write, and execute the file.

⚡ Summary

• Linux permissions control who can read, write, or execute files and directories.
• Permissions are grouped into owner, group, and others.
• You can use either symbolic (rwx) or numeric (755, 644) notation.
• Use chmod to modify permissions easily.