Blog 2: Computer, Linux & Cloud Servers (Made Simple)

🧠 Blog 2: What is a Computer, Linux & Cloud Servers? (Made Simple)

By Kalyan Kalavena
All rights reserved – Only the author may edit this content.

💻 What is a Computer?

A computer is like a smart brain. It takes input, processes it, and gives output.

  • RAM – Memory that helps apps run fast
  • Storage – Saves your files
  • OS – Software like Windows/Linux that lets you use the computer
  • Processor – The brain of the computer

🌍 What is Client-Server Architecture?

Imagine visiting a restaurant:

  • Client = You (browser)
  • Server = Kitchen (host app like facebook.com)

Type facebook.com → browser talks to server → you see the website.

Port Forwarding lets you share your laptop app on the internet.

🐧 What is Linux?

Linux is a free, secure, fast OS used in cloud servers.

  • Region = Location (HYD, Mumbai, etc.)
  • AZ = Data centers (e.g., North HYD, South HYD)
  • Instance = Server = Node

Linux Flavours (Distributions)

  • Ubuntu
  • RHEL
  • CentOS
  • Fedora
  • Android (based on Linux)

Inside Linux

  • Kernel = Brain of OS, built using C language
  • User Interface = What users see and interact with

Invented by Linus Torvalds. Open Source means anyone can use/improve it.

🔐 Firewall (Security Group)

  • Inbound = Who can enter
  • Outbound = Who can leave

To allow all internet traffic: 0.0.0.0/0

🧩 What is AMI?

AMI = Amazon Machine Image
A pre-built OS setup for AWS EC2, like a Windows .iso file.

🛡️ Authentication Methods

  1. What you know – Password
  2. What you have – OTP, token
  3. What you are – Fingerprint, retina

Public & Private Keys

  • Public = Lock
  • Private = Key
ssh-keygen -f my-key

📁 Linux File Basics


pwd       # Current directory
ls -l     # List files with details
cd ..     # Go back one folder

Key File Types

  • .pub = Public Key
  • .pem = Private Key

SSH Command

ssh -i my-key.pem ec2-user@<Your-IP>

⚙️ EC2 Setup Flow

  1. Create keys
  2. Import public key to AWS
  3. Create firewall rules
  4. Launch EC2 instance
  5. Connect via SSH
  6. Terminate after use

🧠 Recap

  • Computer = RAM + Storage + OS + Processor
  • Linux = Secure, Open Source OS for servers
  • AMI = Pre-configured OS in AWS
  • SSH = Secure login to cloud server

Created by Kalyan Kalavena

© 2025 Kalyan Kalavena – DevSecOps Blog Series. Patent rights reserved. Not for editing or reproduction.

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