1. Understand Linux Basics
Before learning Linux administration, you should first understand what an Operating System is, how it works, and where Linux fits in.
1.1 What is an Operating System?
An Operating System (OS) is system software that works as a bridge between the user, applications, and computer hardware.
Simple Definition
Operating System = Software that manages computer hardware and provides a platform to run applications.
For example:
👤 USER ↓ Applications Chrome | VS Code | VLC ↓ 🖥️ OPERATING SYSTEM Windows | Linux | macOS ↓ HARDWARE CPU | RAM | Disk | Network | USB
Real-Life Example
Suppose you open Google Chrome.
You don't directly tell the CPU:
"Take 500 MB RAM and execute these instructions."
Instead, Chrome asks the Operating System for resources.
The OS manages:
- CPU
- RAM
- Hard disk/SSD
- Network
- Keyboard
- Mouse
- Display
- Files
- Users
- Security
1.2 Main Functions of an Operating System
|
Function |
What it does |
Example |
|
Process Management |
Manages running programs |
Chrome, Python, Docker |
|
Memory Management |
Manages RAM |
Gives RAM to applications |
|
File Management |
Manages files/directories |
/home/user/file.txt |
|
Device Management |
Controls hardware devices |
USB, printer, disk |
|
User Management |
Manages users/accounts |
root, sandeep |
|
Security |
Controls access |
File permissions |
|
Networking |
Manages network communication |
IP, DNS, TCP |
|
Resource Management |
Allocates system resources |
CPU/RAM/Disk |
|
Application Management |
Provides environment for apps |
Python, Apache, Nginx |
1.3 Examples of Operating Systems
Desktop / Laptop
- Windows
- Linux
- macOS
Mobile
- Android
- iOS
Servers
- Ubuntu Server
- Red Hat Enterprise Linux (RHEL)
- Rocky Linux
- AlmaLinux
- Debian
- SUSE Linux Enterprise
1.4 What is Linux?
Linux is an open-source operating-system kernel.
In everyday conversation, people commonly say "Linux" to refer to a complete Linux-based operating system, such as Ubuntu or Debian.
Think of it like this:
Linux Kernel + System Utilities + Libraries + Package Manager + Applications ↓ Linux Distribution
Examples:
Ubuntu Debian RHEL Rocky Linux AlmaLinux Fedora Arch Linux
1.5 What is a Kernel?
The kernel is the core part of an operating system.
It communicates between software and hardware.
Applications ↓ System Calls ↓ 🐧 Linux Kernel ↓ Hardware ┌────┬────┬────┬─────┐ CPU RAM Disk Network
Example
You run:
ls
The ls command needs information from the filesystem.
The Linux kernel helps the command access the required filesystem resources.
1.6 Linux vs Windows
|
Feature |
Linux |
Windows |
|
Source |
Mostly open source |
Proprietary |
|
Command Line |
Very powerful |
CMD / PowerShell |
|
Common Server Use |
Very common |
Very common |
|
File System |
/, /home, /etc etc. |
C:\, D:\ etc. |
|
Package Management |
apt, dnf, yum etc. |
Windows Package Manager / installers |
|
Permissions |
Owner/Group/Others |
ACL-based permissions |
|
Root/Admin |
root |
Administrator |
|
Automation |
Shell scripting |
PowerShell / batch |
|
DevOps |
Very widely used |
Also used |
1.7 What is a Linux Distribution?
A Linux distribution (distro) is a complete operating system built around the Linux kernel.
Popular distributions
|
Distribution |
Common Use |
|
Ubuntu |
Beginners, servers, cloud |
|
Debian |
Stable servers |
|
RHEL |
Enterprise |
|
Rocky Linux |
Enterprise-compatible environments |
|
AlmaLinux |
Enterprise-compatible environments |
|
Fedora |
New technologies/development |
|
Arch Linux |
Advanced users |
Example
When you create an Ubuntu EC2 instance on AWS, you are using:
AWS EC2 ↓ Ubuntu Linux ↓ Linux Kernel ↓ CPU / RAM / Disk / Network
1.8 Linux Architecture
A basic Linux architecture looks like this:
┌───────────────────────────────┐ │ USER │ └───────────────┬───────────────┘ ↓ ┌───────────────────────────────┐ │ APPLICATIONS │ │ Chrome | Python | Nginx | Git │ └───────────────┬───────────────┘ ↓ ┌───────────────────────────────┐ │ SHELL / CLI │ │ Bash | Zsh | Other shells │ └───────────────┬───────────────┘ ↓ ┌───────────────────────────────┐ │ LINUX KERNEL │ │ Process | Memory | Filesystem │ │ Network | Devices | Security │ └───────────────┬───────────────┘ ↓ ┌───────────────────────────────┐ │ HARDWARE │ │ CPU | RAM | Disk | Network │ └───────────────────────────────┘
1.9 What is a Shell?
A shell is a program that allows you to communicate with Linux using commands.
For example:
pwd ls cd mkdir touch cp mv rm
A common Linux shell is Bash.
Example
You type:
pwd
Bash interprets the command and asks the operating system to provide the current directory.
Output might be:
/home/sandeep
1.10 GUI vs CLI
Linux can be managed using:
GUI — Graphical User Interface
You click:
📁 Files 📄 Documents ⚙️ Settings
CLI — Command Line Interface
You type:
ls cd Documents mkdir project
For Linux System Administration and DevOps, CLI is extremely important.
1.11 Why Linux is Important for System Administrators
As a Linux Administrator, you may manage:
Users ↓ Files & Permissions ↓ Processes ↓ Services ↓ Networking ↓ Storage ↓ Security ↓ Monitoring ↓ Backup ↓ Automation
For example, a Linux administrator may need to:
create a user install software configure SSH check CPU/RAM manage services configure firewall manage disks check logs set permissions backup data troubleshoot network problems
1.12 Your First Linux Commands
Start with these commands on your Ubuntu system:
|
Command |
Purpose |
Example |
|
pwd |
Show current directory |
pwd |
|
ls |
List files |
ls |
|
cd |
Change directory |
cd /tmp |
|
mkdir |
Create directory |
mkdir project |
|
touch |
Create file |
touch test.txt |
|
cat |
Display file |
cat test.txt |
|
cp |
Copy |
cp a.txt b.txt |
|
mv |
Move/rename |
mv a.txt new.txt |
|
rm |
Delete |
rm test.txt |
|
whoami |
Show current user |
whoami |
|
hostname |
Show computer name |
hostname |
|
date |
Show date/time |
date |
|
clear |
Clear terminal |
clear |
Practice-
Run:
pwd whoami hostname date ls
Then:
mkdir linux-practice cd linux-practice touch test.txt ls
You should understand what happened:
mkdir linux-practice ↓ Created directory cd linux-practice ↓ Entered directory touch test.txt ↓ Created file ls ↓ Displayed test.txt
1.13 Level 1 — Linux Fundamentals Checklist
Use this as your learning checklist:
|
# |
Topic |
Status |
|
1 |
What is an Operating System? |
☐ |
|
2 |
What is Linux? |
☐ |
|
3 |
What is Linux Kernel? |
☐ |
|
4 |
Linux Distributions |
☐ |
|
5 |
Linux Architecture |
☐ |
|
6 |
What is Shell? |
☐ |
|
7 |
Bash basics |
☐ |
|
8 |
CLI vs GUI |
☐ |
|
9 |
Linux filesystem concept |
☐ |
|
10 |
Basic Linux commands |
☐ |
|
11 |
Users and groups |
☐ |
|
12 |
File permissions |
☐ |
|
13 |
Processes |
☐ |
|
14 |
Services |
☐ |
|
15 |
Networking basics |
☐ |
|
16 |
Package management |
☐ |
|
17 |
Logs |
☐ |
|
18 |
Disk/storage basics |
☐ |
|
19 |
SSH |
☐ |
|
20 |
Basic troubleshooting |
☐ |
Recommended learning order
LEVEL 1 Linux Basics ↓ Terminal & Bash ↓ Filesystem ↓ Files & Directories ↓ Users & Groups ↓ Permissions ↓ Processes ↓ Services ↓ Networking ↓ Packages ↓ Logs ↓ Storage ↓ SSH ↓ Basic Troubleshooting
Next topic: 2. Linux Installation & Environment — Ubuntu VM/WSL/EC2, terminal, login, sudo, and basic practice setup.
