EC2 Basics & Instance Launch · 02

What is Amazon EC2?

EC2 (Elastic Compute Cloud) is AWS's Infrastructure as a Service (IaaS) offering.

Amazon EC2 Capabilities
├── Rent Virtual Machines ──────────▶ EC2 Instances
├── Store Data on Virtual Drives ───▶ EBS (Elastic Block Store)
├── Distribute Load ────────────────▶ ELB (Elastic Load Balancer)
└── Scale Services ─────────────────▶ ASG (Auto Scaling Group)

Fundamental AWS Service

Knowing EC2 is fundamental to understanding how the cloud works. It's the ability to rent compute on demand.

EC2 Instance Configuration Options

Component	Options	Notes
Operating System	Linux, Windows, Mac OS	Linux most popular
CPU	Number of vCPUs/cores	Compute power
RAM	Amount of memory	Random Access Memory
Storage	Network (EBS/EFS) or Hardware (Instance Store)	See storage section
Network	Speed, Public IP	Network card type
Firewall	Security Groups	Control traffic
Bootstrap	EC2 User Data	First-launch script

EC2 User Data (Bootstrap Script)

Key Concept

EC2 User Data runs only once at first instance launch with root user privileges (sudo).

Purpose

Automate boot tasks:

Install updates
Install software
Download files from internet
Configure the instance

Example: Web Server Setup

#!/bin/bash
# Update packages
yum update -y
# Install Apache web server
yum install -y httpd
# Start and enable httpd
systemctl start httpd
systemctl enable httpd
# Create web page
echo "Hello World from $(hostname -f)" > /var/www/html/index.html

Boot Time Impact

More commands in User Data = longer boot time. Keep scripts efficient.

EC2 Instance Types Overview

Free Tier: t2.micro

Spec	Value
vCPU	1
Memory	1 GB
Storage	EBS only
Network	Low to Moderate
Free Tier	750 hours/month

Instance Type Examples

Type	vCPU	Memory	Network	Use Case
t2.micro	1	1 GB	Low-Moderate	Free tier, testing
t2.xlarge	4	16 GB	Moderate	Small apps
c5d.4xlarge	16	32 GB	Up to 10 Gbps	Compute-intensive
r5.16xlarge	64	512 GB	20 Gbps	Memory-intensive

Launching Your First EC2 Instance

Step 1: Name and Tags

Name: My First Instance
(Creates a "Name" tag automatically)

Step 2: Choose AMI (Amazon Machine Image)

Quick Start: Amazon Linux 2 (Free tier eligible)
Architecture: 64-bit (x86)

Amazon Linux 2

Recommended for learning - comes with AWS CLI pre-installed.

Step 3: Instance Type

Select t2.micro (Free tier eligible)
Compare types: Click "Compare instance types" link

Step 4: Key Pair (for SSH)

Create new key pair:

Name: EC2Tutorial
Type: RSA
Format:
- .pem → Mac, Linux, Windows 10+
- .ppk → Windows 7/8 (PuTTY)

Download Immediately

Key pair downloads only once. Store securely - you cannot retrieve it later.

Step 5: Network Settings

Security Group (Firewall):

launch-wizard-1 (auto-created)
├── Inbound Rules
│   ├── SSH (Port 22) ──────▶ From: 0.0.0.0/0 (Anywhere)
│   └── HTTP (Port 80) ─────▶ From: 0.0.0.0/0 (Anywhere)
└── Outbound Rules
    └── All Traffic ────────▶ To: 0.0.0.0/0 (Anywhere)

✅ Allow SSH traffic from Anywhere
✅ Allow HTTP traffic from the internet
❌ HTTPS (not needed for this demo)

Step 6: Storage Configuration

Root Volume
├── Size: 8 GB
├── Type: gp2 (General Purpose SSD)
└── Delete on termination: Yes ✓

Delete on Termination

Default is Yes - volume deleted when instance terminates. Change to No if you need persistent data.

Step 7: Advanced Details - User Data

Paste the web server script in User Data field:

#!/bin/bash
yum update -y
yum install -y httpd
systemctl start httpd
systemctl enable httpd
echo "Hello World from $(hostname -f)" > /var/www/html/index.html

Step 8: Launch

Review summary
Click Launch Instance
Instance state: Pending → Running (~10-15 seconds)

Launching an EC2 instance, step by step

The wizard has eight steps. The Security Group, root volume and User Data are all set before launch.

Accessing Your Instance

Web Server Access

http://<PUBLIC_IPv4_ADDRESS>

Use HTTP, Not HTTPS

Use http:// (port 80), NOT https:// (port 443). HTTPS will timeout since we didn't configure it.

Instance Details

Property	Example	Notes
Instance ID	i-0abc123def456	Unique identifier
Public IPv4	54.123.45.67	For external access
Private IPv4	172.31.33.135	Internal AWS network
Instance State	Running	Current status

Instance Lifecycle

States

┌─────────┐    Launch    ┌─────────┐
│ Stopped │─────────────▶│ Pending │
└─────────┘              └────┬────┘
     ▲                        │
     │ Stop                   ▼
     │                   ┌─────────┐
     └───────────────────│ Running │
                         └────┬────┘
                              │ Terminate
                              ▼
                         ┌────────────┐
                         │ Terminated │
                         └────────────┘

Actions

Action	Effect	Billing
Stop	Shutdown, keep EBS	No compute charge
Start	Boot from EBS	Resume billing
Terminate	Delete instance + EBS (if delete on term)	Stop billing

Instance states

Stopping keeps the EBS volume and ends compute charges. Terminating deletes the instance for good.

IP Address Behavior

Public IP Changes on Stop/Start

When you stop and start an instance, the Public IPv4 may change. The Private IPv4 stays the same.

Before Stop:
├── Public IP: 54.123.45.67
└── Private IP: 172.31.33.135

After Start:
├── Public IP: 3.250.12.89  ← CHANGED!
└── Private IP: 172.31.33.135  ← Same

Questions & Answers

Q1: When does EC2 User Data script run?

Answer:

EC2 User Data runs only once at the first launch of the instance. It never runs again, even after stop/start. It runs with root user privileges.

Q2: What happens to the Public IP when you stop and start an instance?

Answer:

The Public IPv4 address may change when you stop and start an instance. The Private IPv4 address stays the same. Use Elastic IP if you need a static public IP.

Q3: What's the difference between Stop and Terminate?

Answer:

Stop: Instance shuts down, EBS volume preserved, no compute charges, can restart later
Terminate: Instance deleted, EBS deleted (if delete on termination = yes), cannot recover

Q4: Why is my web server showing timeout instead of the page?

Answer:

Check:

Using http:// not https://
Security group has port 80 (HTTP) open
Wait 2-5 minutes for User Data script to complete
Instance is in "Running" state

Check yourself

Quiz

Flashcards

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