Fundamentals
Computing Basics
Virtual machines, operating systems, Linux, servers, kernels, SSH, and terminal commands — everything explained with real-world analogies and zero assumptions.
9 sections
covering core topics
~35 min
estimated reading
Beginner
no prerequisites
What is a Virtual Machine (VM)?
A Virtual Machine is basically a computer inside a computer. It's a software-based version of a physical computer that runs its own operating system and applications, just like a real computer would — but it lives inside your actual computer.
Why Do People Use Virtual Machines?
Let me give you some real scenarios:
Warning
Never open suspicious files on your real machine! Use a Virtual Machine as a sandbox. Whatever happens inside stays inside — your real computer stays completely safe.
How Does It Actually Work?
Here's the simple flow: Your Physical Computer (Host) runs a special software called a Hypervisor, which creates and manages Virtual Machines (Guests).
- Host Machine = Your real, physical computer
- Guest Machine = The Virtual Machine running inside it
- Hypervisor = The software that makes it all possible
Think of the Hypervisor as a building manager who divides a large house into apartments and makes sure each apartment gets its fair share of electricity, water, etc. Each apartment (VM) operates independently, but they all share the same building (your physical computer).
How 16GB RAM Gets Split Among VMs
Total: 16GB
Popular VM Software
VirtualBox
Free, by Oracle — great for beginners
VMware Workstation
Popular in professional settings
Hyper-V
Built into Windows Pro
Parallels
Popular for Mac
Key Takeaway
A Virtual Machine is a software-based computer running inside your real computer. A Hypervisor divides your physical resources among VMs. This is how companies like Amazon and Google efficiently run thousands of services on fewer physical machines.
What is an Operating System?
An Operating System is the main software that runs your computer. It's the middleman between you (the user) and the hardware (CPU, RAM, hard drive, etc.). Without an OS, your computer is just a useless box of metal and wires.
Think of your computer hardware as a car engine, and the Operating System as the steering wheel, pedals, and dashboard. The engine is powerful, but without the steering wheel and pedals, you can't drive the car. The OS gives you the controls to use the hardware.
The Big Three Operating Systems
| OS | Made By | Used On |
|---|---|---|
| Windows | Microsoft | Most PCs and laptops |
| macOS | Apple | MacBooks and iMacs only |
| Linux | Community (open-source) | Servers, devs, Android, and more |
Key Takeaway
The Operating System is the middleman between you and your hardware. The three major operating systems are Windows (Microsoft), macOS (Apple), and Linux (community-built and free).
What is Linux?
Linux IS an Operating System — just like Windows and macOS. But here's where it gets interesting — Linux is a little different from Windows and macOS. Let me explain how.
1. Linux is FREE and Open Source
Windows — You pay Microsoft for a license (it's usually included when you buy a laptop, but someone paid for it).
macOS — You can only get it on Apple hardware, which is expensive.
Linux — Completely FREE. Anyone can download, use, modify, and even redistribute it. The code is open for everyone to see and improve.
2. Linux Has Many “Flavors” (Distributions)
Unlike Windows where there's just Windows 10, 11, etc., Linux comes in hundreds of versions made by different teams. These versions are called distributions (distros).
Popular Linux Distributions
| Distro | Best For |
|---|---|
| Ubuntu | Beginners (most popular, easy to use) |
| Linux Mint | People switching from Windows (looks similar) |
| Fedora | Developers |
| Kali Linux | Cybersecurity and ethical hacking |
| Arch Linux | Advanced users who want full control |
| CentOS / Rocky Linux | Servers in companies |
3. Linux is EVERYWHERE
Did You Know?
You already use Linux without knowing it! Android phones? Built on Linux. Netflix, Google, Facebook, Amazon? All run on Linux servers. Smart TVs, routers, traffic lights, space stations? Many run Linux. Even Tesla cars run on Linux!
Windows vs macOS vs Linux
| Feature | Windows | macOS | Linux |
|---|---|---|---|
| Price | Paid | Comes with Apple hardware | Free |
| Source Code | Closed (secret) | Closed (secret) | Open (anyone can see/modify) |
| Ease of Use | Easy | Easy | Depends on distro (Ubuntu is easy) |
| Customization | Limited | Very limited | Extremely customizable |
| Gaming | Best for gaming | Decent | Improving, but not the best yet |
| Security | Most targeted by viruses | More secure | Very secure |
| Used For | Home, office, gaming | Creative work, Apple ecosystem | Servers, development, hacking, everything |
Key Takeaway
Linux is free, open source, and comes in many distributions (flavors). While Windows dominates personal desktops, Linux absolutely dominates servers, phones (Android), IoT devices, and the internet.
Why Linux is Used Everywhere
Now the big question — why does Linux power almost everything? There are several strong reasons that make Linux the dominant force in computing infrastructure.
Reason 1: It's FREE (Zero Cost)
Imagine you're a company and you need to run 10,000 servers (like Google or Amazon does). If you use Windows Server, you'd need to pay Microsoft a license fee for each server. That could be millions of dollars. With Linux? $0. Zero. Nothing.
Reason 2: It's Extremely Customizable
Since the source code is open, companies can modify Linux to fit their exact needs. You can't do this with Windows or macOS — their code is locked.
Reason 3: It's Super Stable and Reliable
Think about your Windows computer. How many times have you seen the blue screen of death? How many times has Windows forced you to restart for updates? Now think about Google.com. Has Google.com ever gone down for a Windows update? No. That's because Google runs on Linux, and Linux servers can run continuously for months or even years without needing a restart.
Reason 4: It's Incredibly Secure
Linux is much more secure than Windows for two key reasons: fewer viruses target Linux, and the open-source model means thousands of security experts constantly check the code.
Imagine two houses. House A (Windows) has a locked door, but nobody is allowed to inspect the lock. If there's a weakness, only the company knows — and they might take months to fix it. House B (Linux) has a lock that everyone can inspect. Thousands of security experts around the world are constantly checking it. If someone finds a vulnerability, it gets fixed within hours or days, not months.
Reason 5: It's Lightweight and Fast
Linux can run on anything — from a massive server with 128 CPUs to a tiny Raspberry Pi the size of a credit card. Old, slow computers that can barely run Windows 11 will run fast and smooth with a lightweight Linux distro like Lubuntu.
Did You Know?
100% of the world's top 500 supercomputers run Linux — literally ALL of them! Linux also powers IoT devices (smart thermostats, fridges, routers), embedded systems (ATMs, traffic lights, airport displays), and more.
Key Takeaway
Linux dominates because it's free ($0), extremely customizable (Android, Amazon Linux, Tesla), super stable (runs for years), incredibly secure (open-source advantage), and lightweight (runs on anything from a Raspberry Pi to a supercomputer).
What is a Server?
A server is indeed a computer. It has a CPU, RAM, storage, and a network connection — just like your laptop or desktop. But there are some key differences between a regular computer and a server.
Think of a regular computer as a family car (like a Honda Civic). It's built for one person or family to use daily — comfortable, has a radio, AC, looks nice. Now think of a server as a heavy-duty truck (like an 18-wheeler). It's not pretty, it's not comfortable, but it's built to carry heavy loads, run long distances, and work non-stop.
Regular Computer vs Server
| Feature | Your Regular Computer | A Server |
|---|---|---|
| Purpose | For YOU to browse, game, work | To SERVE data/services to many people |
| Users | One person (you) | Hundreds, thousands, or millions |
| Runs 24/7? | No, you turn it off at night | Yes, it runs 24/7, 365 days a year |
| Hardware | Moderate (8-32 GB RAM, 1 CPU) | Very powerful (128-1024+ GB RAM, multiple CPUs) |
| Screen/Keyboard? | Yes, you sit in front of it | Usually NO — managed remotely |
| Location | Your desk or lap | In a data center |
Real-World Example: How YouTube Works
When you open YouTube on your phone, your phone doesn't have all those videos stored inside it. So what happens?
You type youtube.com or open the app
Your phone sends a request over the internet: "Hey, I want to watch this video"
That request travels to one of Google's servers in a data center somewhere
The server finds the video, processes it, and sends it back to your phone
You watch the video
Key Takeaway
A server is a powerful computer designed to serve data and services to many users simultaneously. It runs 24/7, usually has no screen or keyboard, and is managed remotely. That's why it's called a “server” — it literally serves you!
What is the Kernel?
A kernel is the core part of an operating system that sits between your hardware (CPU, RAM, storage, keyboard, screen, etc.) and your software (apps like Chrome, Spotify, games, etc.). Its job is to make them talk to each other.
Imagine you're an English speaker visiting a Chinese restaurant in China. You don't speak Chinese, and the chef doesn't speak English. You need a translator sitting between you and the chef. You (the customer) = the software/apps. The chef = the hardware. The translator = the KERNEL. You tell the translator “I want fried rice” (you click a file). The translator tells the chef in Chinese (kernel tells CPU/RAM). The chef cooks it (hardware processes). The translator brings it back in English (kernel sends result to your app).
What Does the Kernel Actually Do?
Kernel vs Operating System
Think of a car. The engine = the Kernel (the most critical part that makes everything run). The full car (engine + body + seats + steering wheel + dashboard + AC + radio) = the Operating System. You can't drive just an engine on the road — you need the full car wrapped around it.
Kernel vs Operating System
| Component | What It Is |
|---|---|
| Kernel | The engine — handles hardware communication, memory, processes |
| Operating System | The full car — kernel + desktop + apps + file manager + everything |
The Computing Layer Stack
Top = closest to user | Bottom = closest to hardware
Key Takeaway
The kernel is the core engine of the operating system that translates between your apps and your hardware. Without it, your apps can't use the CPU, RAM, storage, or any device. The OS is the full package built around the kernel.
Linux Distros & Ubuntu
Now that you understand what a kernel is, this will make much more sense. Linux is JUST the kernel — just the engine. It was created by Linus Torvalds in 1991. By itself, you cannot sit down and use just the Linux kernel — there's no desktop, no apps, no file manager, nothing visual.
So How Do People Actually Use Linux?
Different teams take the Linux kernel (engine) and build a complete operating system around it by adding a graphical desktop, a file manager, pre-installed apps, a software store, themes, settings, and tools. This complete package is called a Linux Distribution (Distro).
Imagine the Linux kernel is a car engine. Different car companies take that same engine and build completely different cars around it: Toyota takes the engine and builds a reliable family car — that's like Ubuntu. Ferrari takes it and builds a sports car — that's like Kali Linux. Jeep takes it and builds an off-road beast — that's like Arch Linux. Honda takes it and builds something smooth and familiar — that's like Linux Mint. They ALL have the same engine inside (Linux kernel), but the car around it looks, feels, and behaves differently.
Ubuntu Specifically
Ubuntu = Linux kernel + GNOME desktop + Software Center + pre-installed apps + tons of user-friendly features, all packaged together by a company called Canonical.
It's the most popular distro for beginners because:
It's free
Easy to install and use
Clean, modern look
Huge community
Key Takeaway
Linux is just the kernel (engine). A distro is a complete OS built around that kernel. Ubuntu is the most popular beginner-friendly distro, maintained by Canonical. All distros share the same Linux kernel but differ in everything else.
What is SSH?
SSH stands for Secure Shell. It's a way to remotely control another computer using just text commands, over the internet or a network — securely. You sit at your computer and type commands that travel through SSH to the remote computer, which executes them.
Why is it Called “Secure” Shell?
Warning
Before SSH, there was Telnet which did the same thing — let you control a remote computer. But Telnet sent everything as plain text, meaning anyone snooping on the network could see your password, your commands, everything. SSH encrypts all communication. Never use Telnet for anything sensitive!
When Do People Use SSH?
Remember we talked about servers — powerful computers in data centers with no screen or keyboard? So how does an engineer manage them? They SSH into the server from their laptop!
Click the Play button above to start!
Watch the commands execute step by step
Key Takeaway
SSH (Secure Shell) lets you remotely control another computer using encrypted text commands. It's how engineers manage servers that have no screen or keyboard — all from their own laptop, from anywhere in the world.
Linux Commands: sudo, apt, update & upgrade
Let's break down one of the most common Linux commands you'll ever use: sudo apt update && sudo apt upgrade -y. There are 4 key parts: sudo, apt, update/upgrade, and &&.
1. sudo = “Run as Admin/Boss”
sudo stands for “Super User DO”.
Imagine you work at an office. Regular employees can do basic things — use the printer, sit at their desk. But some actions require the boss's permission — like accessing the safe, or changing company policies. When you add sudo before a command, you're saying “I want to do this as the boss (administrator)”.
2. apt = The App Store (for the Terminal)
apt stands for Advanced Package Tool. It's Ubuntu's software manager — like the App Store on your iPhone or Google Play Store on Android, but instead of tapping icons, you type commands.
3. update vs upgrade
These two words sound similar but do very different things:
sudo apt update“Check what's new”
Refreshes the list of available updates. It does NOT install anything.
sudo apt upgrade -y“Install all updates”
Actually downloads and installs all new versions. -y means “yes to everything”.
Imagine you go to a restaurant and ask the waiter “What's new on the menu today?” The waiter tells you what's available. You haven't ordered anything yet — you're just checking. That's apt update.
4. && = “If the first succeeds, then do the next”
The && connects two commands. It means: run the first command, and only if it succeeds, run the next one. It makes no sense to install updates (upgrade) if you haven't checked what's available (update) first — it's like ordering food before seeing the menu.
Click the Play button above to start!
Watch the commands execute step by step
Key Takeaway
sudo = run as admin. apt = package manager. update = check for new versions. upgrade = install them. && = only continue if the first command succeeds. Together: sudo apt update && sudo apt upgrade -y is the most common command to keep your system up to date.
Computing Basics Quiz
What is a Hypervisor?
Key Concepts Flashcards
Click any card to flip and reveal the definition.