linux doc: perm doc

Linux/LPIC1/19-chmod-chown.md

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+# 📁 Linux File Permissions: A Quick & Clear Guide
+
+---
+
+## 🔍 Example: Output of `ls -lh`
+
+Run this command in your terminal:
+
+```bash
+ls -lh
+```
+
+Example output:
+
+```bash
+drwxr-xr-x 3 root root 4.0K Jul  1 22:22 dir1
+-rw-r--r-- 1 root root 2.0G Jul  1 21:59 test2.tar
+```
+
+---
+
+## 🧠 Understanding the Output Columns
+
+| Column               | Description                             |
+| -------------------- | --------------------------------------- |
+| `d` / `-`            | File type (`d` = directory, `-` = file) |
+| `rwxr-xr-x`          | Permissions (user, group, others)       |
+| `3`                  | Number of hard links                    |
+| `root`               | Owner (user)                            |
+| `root`               | Group                                   |
+| `4.0K` / `2.0G`      | File size                               |
+| `Jul 1 22:22`        | Last modification date                  |
+| `dir1` / `test2.tar` | File or directory name                  |
+
+---
+
+## 🔤 First Character: File Type Indicator
+
+* `d` → Directory 📂
+* `-` → Regular file 📄
+
+---
+
+## 🔠 File Permissions Breakdown
+
+```
+drwxr-xr-x
+│││ │ │ │
+│││ │ │ └─ Permissions for Others (o)
+│││ │ └── Permissions for Group (g)
+│││ └──── Permissions for User (u)
+│└──────── File type (d = directory, - = file)
+└───────── Read (r), Write (w), Execute (x)
+```
+
+---
+
+## 🔐 Permission Symbols Explained
+
+| Symbol | Meaning |
+| ------ | ------- |
+| `r`    | Read    |
+| `w`    | Write   |
+| `x`    | Execute |
+
+---
+
+## 👥 Permission Entities
+
+| Symbol | Meaning      |
+| ------ | ------------ |
+| `u`    | User (owner) |
+| `g`    | Group        |
+| `o`    | Others       |
+| `a`    | All          |
+
+---
+
+## 🔢 Numeric Permission Values (Octal)
+
+| Value | Binary | Permissions | Meaning                |
+| ----- | ------ | ----------- | ---------------------- |
+| 0     | 000    | ---         | No permissions         |
+| 1     | 001    | --x         | Execute only           |
+| 2     | 010    | -w-         | Write only             |
+| 3     | 011    | -wx         | Write + Execute        |
+| 4     | 100    | r--         | Read only              |
+| 5     | 101    | r-x         | Read + Execute         |
+| 6     | 110    | rw-         | Read + Write           |
+| 7     | 111    | rwx         | Read + Write + Execute |
+
+---
+
+## 🛠️ Changing Permissions with `chmod`
+
+### Syntax:
+
+```bash
+chmod [permissions] [filename]
+```
+
+### Example (numeric):
+
+```bash
+chmod 755 myscript.sh
+```
+
+### What does `755` mean?
+
+| Entity | Value | Permission                 |
+| ------ | ----- | -------------------------- |
+| User   | 7     | rwx (read, write, execute) |
+| Group  | 5     | r-x (read, execute)        |
+| Others | 5     | r-x (read, execute)        |
+
+### Recursive permission change:
+
+```bash
+chmod -R <permission> <directory>
+```
+
+---
+
+## 👑 Changing Ownership with `chown`
+
+### Syntax:
+
+```bash
+chown [options] owner[:group] file
+```
+
+### Examples:
+
+Change owner only:
+
+```bash
+sudo chown radin file.txt
+```
+
+Change owner and group:
+
+```bash
+sudo chown radin:dev file.txt
+```
+
+Change owner and group recursively (for directories):
+
+```bash
+sudo chown -R radin:dev files/
+```