Linux Fundamentals

01 Introduction to Operating Systems

Before Linux, understand the job every operating system does.

A computer is just electronics — a processor (CPU) that does maths, memory (RAM) that holds work-in-progress, and storage (disk) that keeps files. On its own, that hardware doesn't know how to open a photo or run a browser.

Hardware vs Software

What an operating system is responsible for

The three you'll meet most

02 History of Linux

Where it came from — and why that story still shapes how Linux works.

Linux didn't appear out of nowhere. It's the latest chapter in a 50-year story that began with UNIX at Bell Labs.

Why Linux succeeded

• Free & open source — no licence fees; the code is public.
• A global community — thousands of contributors fix and improve it daily.
• It runs anywhere — from a $5 sensor to the world's fastest supercomputers.

03 Why Learn Linux?

The payoff — before we touch a single command.

What makes Linux special

Where Linux actually runs

04 Linux Architecture

The four layers — from your app down to the metal.

05 The Linux File System

One tree to rule them all — starting at /.

Unlike Windows (with C:, D: drives), Linux has a single tree that starts at the root directory /. Everything hangs off it.

06 The Building Blocks of Linux

The handful of core ideas the system is made of.

Everything you'll do in Linux is really about managing these abstractions:

07 Users and Login

Linux was multi-user from day one.

Many people (or programs) can use one Linux machine at once, each kept separate. There are two kinds of accounts you must know:

Ways to log in

• Console login — typing your username & password at the machine itself.
• SSH — logging into a remote machine securely over the network (how you reach cloud servers):

ssh student@server-ip        # connect to a remote Linux machine

08 The Shell & Terminal

The single most important skill in this whole guide.

Reading a command

ls -l /home/student
# └┬┘  └┬┘  └──────┬──────┘
#  command option    argument

A command has three parts: the command (what to do), options (how to do it, usually starting with -), and arguments (what to do it to).

09 Essential Commands TRY THEM BELOW ↓

The everyday vocabulary of the command line.

🖩 Interactive Linux terminal — try it yourself

This is a safe, simulated Linux shell running in your browser. Nothing here can harm anything. Type a command and press Enter. Start with help, then try ls, pwd, cd Documents, cat notes.txt, whoami.

10 File Permissions

The heart of Linux security — who can do what.

Every file and folder answers three questions for three groups of people. The questions are Read (r), Write (w), and Execute (x). The people are the Owner, the Group, and Others.

-rwxr-xr--   1 student staff  # what ls -l shows you
 │└┬┘└┬┘└┬┘
 │ │  │  └ others: r--  (read only)
 │ │  └─── group:  r-x  (read + execute)
 │ └────── owner:  rwx  (read + write + execute)
 └──────── type:   -    (- = file, d = directory)

🧮 chmod calculator — click the boxes

Permissions are often written as a 3-digit number. Toggle what each group can do and watch the number build:

Commands

11 Process Management

Everything running is a process — here's how to watch and control them.

A process is a running program. Each has a unique number (PID). Processes can start other processes (a parent starting a child). Some run in the foreground (you wait for them); others in the background (they run while you keep working).

12 Installing Software

No hunting for “.exe” files — Linux uses package managers.

A package manager installs, updates and removes software for you from trusted online repositories — handling dependencies automatically. Which one you use depends on the distribution family:

sudo apt update            # refresh the catalog
sudo apt install git       # install a package
sudo apt upgrade           # update everything

sudo dnf install git       # (older: yum)
sudo dnf update

13 Networking Basics

How your machine finds and talks to others.

14 Services (systemd)

The background programs that keep a server running.

A service (or daemon) is a program that runs quietly in the background — a web server, a database, your monitoring script. On modern Linux, the manager in charge of starting and supervising them is systemd. It's also the first thing that runs when Linux boots.

15 Text Editors

You'll edit config files constantly — pick an editor.

Surviving vi — the one thing beginners must know

vi has modes. This trips everyone up once:

16 Shell Scripting

Turn commands you repeat into a reusable program.

A shell script is just a text file full of commands. It's how you automate — backups, deployments, health checks. Scripts understand variables, conditions, loops and functions.

#!/bin/bash
# greet.sh — a first script

name="$1"                 # $1 = first argument

if [ -z "$name" ]; then
    name="world"
fi

for i in 1 2 3; do
    echo "($i) Hello, $name — welcome to Linux!"
done

chmod +x greet.sh      # make it runnable
./greet.sh Ada         # run it with an argument

17 Environment Variables

Little settings the whole system reads.

Environment variables are named values available to your shell and the programs it runs. A few you'll meet constantly:

echo $HOME             # show one variable
printenv               # show them all
export EDITOR=nano     # set one for this session

18 Linux Administration

Keeping a real system healthy.

# run a backup every day at 2am (crontab -e)
0 2 * * *  tar -czf /backup/home.tgz /home/student

19 Linux Security

A few habits that keep systems safe.

20 Linux in Modern Computing

Where this foundation takes you next.

Every powerful technology below runs on Linux. The commands you just learned — files, permissions, processes, services, networking — are exactly what these tools use under the hood.

✓ Knowledge Check

Quick questions — click an answer to see if you've got it.

21 Hands-on Labs

Reading isn't enough — do these on a real (or virtual) Linux box.

1. 01
   Create your first directory structure and navigate it with absolute & relative paths.
2. 02
   Create, copy, move and delete files with touch, cp, mv, rm.
3. 03
   Edit a file with nano (then try vi) and save it.
4. 04
   Add a new user and group; set a password.
5. 05
   Watch CPU & memory live with htop.
6. 06
   Install a package with apt (or dnf).
7. 07
   Connect to another machine with ssh.
8. 08
   Write and run your first Bash script.
9. 09
   Schedule a daily backup with cron.
10. 10
    Break & fix: stop a service, then diagnose it with systemctl & journalctl.

➜ Your Learning Roadmap

Each step stands on the one before it — that's the whole idea.

📖 Mini Glossary

Plain-English definitions for the words that come up most.