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Linux/LPIC1/directorys.md
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Linux/LPIC1/directorys.md
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# 📁 Linux Directory Structure & Basic Commands
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This document provides an overview of important Linux directories, their types, and essential file management commands.
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---
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## 📂 Directory Types
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| Type | Description |
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| ----------- | ----------------------------------------------------------------------------------- |
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| **Virtual** | Do not reside on disk; dynamically generated by the system (e.g., `/proc`, `/sys`). |
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| **Normal** | Standard directories that store files and data on disk. |
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---
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## 🗂️ Common Linux Directories
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| Directory | Type | Description |
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| --------- | ------- | ----------------------------------------------------------- |
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| `/etc` | Normal | System configuration files |
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| `/opt` | Normal | Optional or third-party software packages |
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| `/bin` | Normal | Essential binary executables for all users |
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| `/sbin` | Normal | System binaries, typically for administrative tasks |
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| `/lib` | Normal | Shared libraries and kernel modules |
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| `/home` | Normal | User home directories |
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| `/proc` | Virtual | Kernel and process information (virtual files) |
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| `/srv` | Normal | Data for services provided by the system (e.g., web, FTP) |
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| `/sys` | Virtual | Kernel devices and system information |
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| `/usr` | Normal | Secondary hierarchy: programs, libraries, and documentation |
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| `/var` | Normal | Variable data: logs, mail, print spool, temporary files |
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| `/dev` | Virtual | Device files (e.g., disk, USB, terminals) |
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| `/mnt` | Normal | Mount point for temporary filesystems |
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| `/boot` | Normal | Boot loader files, kernel images |
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---
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## 🛠️ Basic File & Directory Commands
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| Command | Description |
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| ------- | ---------------------------------------- |
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| `cd` | Change directory |
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| `ls` | List directory contents |
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| `rm` | Remove files or directories |
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| `mkdir` | Create a new directory |
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| `touch` | Create an empty file or update timestamp |
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| `cp` | Copy files or directories |
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| `mv` | Move or rename files or directories |
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### 📘 Examples
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```bash
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cd /etc # Navigate to /etc directory
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ls -l # List files in long format
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rm file.txt # Delete file.txt
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mkdir new_folder # Create a directory named 'new_folder'
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touch file.txt # Create a new empty file
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cp file1.txt file2.txt # Copy file1.txt to file2.txt
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mv file.txt /home/user/ # Move file.txt to another directory
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```
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Linux/LPIC1/runlevels.md
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Linux/LPIC1/runlevels.md
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# Linux Runlevels Guide
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This document outlines the standard runlevels for **Red Hat** and **Debian**-based systems. Runlevels are used by `init` systems to define different states or modes of operation for the system.
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---
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## 📊 Runlevels Overview
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| Runlevel | Description | Red Hat | Debian |
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| -------- | ------------------------------------ | ------------ | --------------- |
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| 0 | Halt | ✅ Supported | ✅ Supported |
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| 1 | Single User Mode | ✅ Supported | ✅ Supported |
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| 2 | Multi-user (No Network) | ❌ (HaveNet) | ✅ Supported |
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| 3 | Multi-user (Network, No GUI) | ✅ Supported | ✅ Supported |
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| 4 | Custom/User Defined | ✅ Supported | ✅ Supported |
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| 5 | Multi-user (GUI Mode) / Halt *(err)* | ❌ (GUI Mode) | ❌ (Halt/Error?) |
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| 6 | Reboot | ✅ Supported | ✅ Supported |
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> 💡 **Note**:
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>
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> * On **Red Hat**, runlevel 5 typically starts the system with a graphical user interface (GUI).
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> * On **Debian**, runlevel 5 is often unused or reserved for custom setups.
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> * Runlevel behavior can be customized depending on system configuration.
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---
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## 🔧 Commands
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### Check Current Runlevel
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```bash
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runlevel
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```
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### Change Runlevel
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```bash
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telinit <runlevel>
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```
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or
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```bash
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init <runlevel>
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```
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> ⚠️ Changing runlevels may stop or restart services. Use with caution, especially on production systems.
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---
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## 📚 Additional Tips
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* Modern Linux systems (especially systemd-based) may not rely on traditional runlevels. Instead, they use *targets*. Example:
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```bash
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systemctl get-default
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systemctl isolate graphical.target
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```
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