Linux Mega Revision & Final Exam Guide

This guide is a consolidated summary of everything covered in the Linux course (Lectures 1-9), designed to prepare you for the final exam.

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1. Fundamentals & Architecture

• Operating System: Manages hardware and software layers.
• Layers: Hardware ↔ Kernel ↔ GNU/Shell ↔ Applications.
• Kernel: Core of the OS. Manages CPU, RAM, and HW connections.
• Distributions (Distros): Kernel + Tools + Desktop + Package Manager. Examples: Ubuntu, Fedora, RedHat.
• Advantages: Stability, Security, Open Source, and Power.

2. Interface (GUI & CLI)

• Desktop: Activities, Top Bar, Dash (Side Bar), System Menu.
• User Types:
  1. Normal: Limited permissions.
  2. Privileged: Uses sudo for administrative tasks.
  3. Root: The ultimate administrator (UID 0).
• CLI Essentials:
  • whoami: Current user.
  • pwd: Current directory path.
  • ls: List files (-l details, -a hidden).
  • cd: Navigate folders.
  • clear: Clean terminal screen.

3. File & Directory Management

• Creation: mkdir (folders), touch (empty files).
• Manipulation: cp (copy), mv (move/rename), rm (delete), rmdir (delete empty folders).
• Editing: nano (save: Ctrl+O, exit: Ctrl+X), echo (> overrides, >> appends).
• Viewing Content:
  • cat: Show full file.
  • less: Scrollable view.
  • head/tail: Start/end of file.
  • tail -f: Follow file updates in real-time.

4. Advanced Search & Sorting

• find . -name "*.js": Search for file names.
• grep "word" file.txt: Search for text inside files.
• sort: Alphabetical order (-r reverse, -u unique).
• wc -l: Count number of lines in a file.

5. User & Group Administration

• User Commands: useradd -m, passwd, userdel -r.
• Group Commands: groupadd, groupdel, usermod -aG, gpasswd -d.
• System Files: /etc/passwd (users), /etc/group (groups), /etc/shadow (passwords).

6. Security & Permissions (chmod)

• Permission String: d | rwx | r-x | r-- (Type | User | Group | Other).
• Types: - (file), d (directory).
• Numeric Mode: Read(4), Write(2), Execute(1).
  • 755: rwxr-xr-x (Common for programs).
  • 644: rw-r--r-- (Common for files).
  • 600: rw------- (Private file).

7. Disk & Storage Management

• Partitioning (fdisk): fdisk /dev/sdb (Commands: n, p, w, q).
• FHS (Filesystem Hierarchy):
  • /bin: Basic commands.
  • /sbin: System commands (admin).
  • /etc: Config files.
  • /home: User data.
  • /dev: Hardware devices.
• LVM (Logical Volume Management):
  • Flexible storage management (PV ➔ VG ➔ LV).
  • pvcreate ➔ vgcreate ➔ lvcreate ➔ mkfs ➔ mount.

🚀 Final Exam Tips:

1. Permissions Calculation: Practice converting rwx to numeric and vice versa (e.g., 755, 644, 700).
2. Pathing: Understand the difference between Root / and Home ~.
3. Basic Commands: Ensure you know the difference between rm and rmdir, and > vs >>.
4. LVM Sequence: Remember the order of creating LVM (PV -> VG -> LV).
5. Processes: Know how to identify a PID using top and terminate it using kill.