Linux File Permissions Explained (No More Confusion)

If you don’t fully understand permissions, you’ll:

• break apps
• expose your server
• get random “Permission denied” errors

Let’s fix that.

📂 Understanding Permissions

Example:

-rwxr-xr-- 1 user user file.sh

Breakdown:

• r = read
• w = write
• x = execute

Groups:

• owner
• group
• others

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🔢 Numeric Permissions

Number	Meaning
7	rwx
6	rw-
5	r-x
4	r–

Example:

chmod 755 file.sh

👤 Change Ownership

chown user:group file

Example:

chown www-data:www-data /var/www/html

⚠️ Common Mistakes

❌ Using:

chmod 777

👉 This gives full access to everyone → security risk

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🔥 Best Practices

• Web apps:

755 for folders
644 for files

• SSH:

chmod 600 ~/.ssh/id_rsa

🧠 Summary

Permissions are critical for both security and stability — master them early.