Day 19: Linux File & Permission System – Complete Guide to chmod, chown & File Security (Hindi)
🐧 Day 19: Linux File & Permission System
(Bug Hunting / Ethical Hacking Course – Day 19)
Aaj ka topic bahut hi important hai 🔥
Agar aap Linux ka File & Permission System samajh gaye, to aap:
✔ Secure system bana sakte ho
✔ Scripts properly run kar sakte ho
✔ Permission errors solve kar sakte ho
✔ Hacking tools ko sahi tarike se execute kar sakte ho
Linux me security ka base hi permission system hai.
🔥 1️⃣ Linux File Types
Linux me mainly 3 types ke files hote hain:
1️⃣ Regular File → text, script, image
2️⃣ Directory → folder
3️⃣ Executable File → program/script
Check karne ke liye:
ls -l
Example output:
-rwxr-xr-- 1 kali kali 120 Feb 10 script.sh
Is line ko samajhna hi aaj ka goal hai 👇
🔥 2️⃣ Permission Structure Samjho (Very Important)
Example:
-rwxr-xr--
Isko 4 parts me divide karo:
- rwx r-x r--
| | | |
| | | Others
| | Group
| Owner
File Type
📌 First Character (File Type)
| Symbol | Meaning |
|---|---|
| - | Regular File |
| d | Directory |
| l | Link |
📌 Next 9 Characters = Permissions
3 groups hote hain:
| Section | Kiske liye? |
|---|---|
| rwx | Owner |
| r-x | Group |
| r-- | Others |
🔥 3️⃣ Permission Meaning
| Letter | Meaning | Number |
|---|---|---|
| r | Read | 4 |
| w | Write | 2 |
| x | Execute | 1 |
🔥 4️⃣ Numeric Permission System (Most Important)
Linux me permission set karne ka easiest method:
Formula:
Add numbers
Example:
| Permission | Calculation | Number |
|---|---|---|
| rwx | 4+2+1 | 7 |
| rw- | 4+2 | 6 |
| r-x | 4+1 | 5 |
| r-- | 4 | 4 |
📌 Common Examples:
chmod 777 file.txt
👉 Sabko full permission (Not secure)
chmod 755 script.sh
👉 Owner full, baaki read + execute (Recommended for scripts)
chmod 644 file.txt
👉 Owner read/write, baaki read only (Safe for normal files)
🔥 5️⃣ chmod Command Deep Understanding
Syntax:
chmod permission filename
Example:
chmod 755 script.sh
📌 Symbolic Method
chmod +x script.sh
👉 Execute permission add karega.
chmod -w file.txt
👉 Write permission remove karega.
🔥 6️⃣ chown Command (Ownership Change)
Owner change karne ke liye:
sudo chown user filename
Example:
sudo chown kali file.txt
Group change karne ke liye:
sudo chown user:group filename
🔥 7️⃣ Real Hacking Scenario
Situation:
Aapne ek script download ki.
Run karte waqt error aaya:
Permission denied
Solution:
chmod +x script.sh
./script.sh
👉 Ye problem 90% beginners ko aati hai.
🔥 8️⃣ Secure Permission Practice
⚠️ Kabhi bhi important files par 777 use mat karo.
Recommended:
| File Type | Permission |
|---|---|
| Normal File | 644 |
| Script File | 755 |
| Sensitive File | 600 |
🧪 Practice Lab (Must Do)
mkdir testlab
cd testlab
touch file.txt
ls -l
chmod 644 file.txt
ls -l
chmod 777 file.txt
ls -l
Output observe karo.
🧠 Real Hacker Advice
✔ Permission samajhna = Linux samajhna
✔ 777 avoid karo
✔ Script run nahi ho raha? Check permission
✔ Always think security first
🎯 Day 19 Final Summary
✔ File type samjha
✔ rwx system samjha
✔ Numeric method master kiya
✔ chmod aur chown use seekha
✔ Secure permission ka concept clear kiya