03. EC2 Instance

EC2

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Prerequisites

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1. EC2 Instance

EC2 is one of the most fundamental services in AWS. It provides Virtual servers in the cloud EC2 allows you to run applications on virtual machines without owning physical hardware.

Instead of:

• Buying servers
• Installing OS
• Managing hardware

👉 You simply:

• Launch an instance
• Choose specifications
• Start using it immediately

In EC2, a server is called an instance. It behaves like a real server, but it is virtual.

Each instance includes:

• CPU (vCPU)
• Memory (RAM)
• Storage (EBS)
• Network capability

2. How EC2 works

[ Physical Server (AWS Data Center) ]
 ├── EC2 Instance (User A)
 ├── EC2 Instance (User B)
 └── EC2 Instance (User C)

👉 Multiple users share the same hardware 👉 Each instance is isolated

AMI is a template used to create instances.

It includes:

• Operating System (Ubuntu, Amazon Linux, etc.)
• Pre-installed software
• Configuration

Think of it as A snapshot of a ready-to-run server

2-1. Basic steps

1. Choose AMI (OS)
2. Select instance type (CPU/RAM)
3. Configure network (VPC, subnet)
4. Add storage
5. Configure security group
6. Launch instance

2-2. Networking

EC2 does not exist alone.

It is placed inside:

• VPC (Virtual Private Cloud)
• Subnet (public / private)

Type	Description
Public	Accessible from internet
Private	Internal only

• Security Group
• Route Table
• Internet Gateway

2-3. Security Group

Security Group acts as a firewall.

Port	Purpose
22	SSH
80	HTTP
443	HTTPS

👉 Only allowed traffic can enter

2-4. Key Pair (Login)

To access EC2:

• Use SSH (Linux)
• Use Key Pair (.pem)

ssh -i key.pem ubuntu@<public-ip>

👉 Password login is not used by default

2-5. Pricing Model

EC2 is pay-as-you-go:

• Charged per usage time

• Different pricing models:

  • On-Demand
  • Reserved
  • Spot

Scenario	Recommended
Testing / short-term	On-Demand
Batch / non-critical	Spot
Stable production	Reserved / Savings Plan
Compliance required	Dedicated

3. How to create EC2

3-1. Search EC2

3-2. Click Navigation pane → “Instances”

3-3. Click Button → “Launch instances”

3-4. Step 1. Set Environments (Hardware)

1. Name and tags: EC2 name
2. Application and OS Images (Amazon Machine Image): Select AMI
3. Instance type: hardware configuration

Type	Description
General Purpose	Balanced CPU & memory
Compute Optimized	High CPU performance
Memory Optimized	Large memory capacity
Accelerated Computing	GPU / FPGA based

• More CPU → faster computation
• More memory → better data handling
• Higher network bandwidth → faster communication
• Higher EBS bandwidth → faster storage I/O

3-5. Step 2. Set Environments (Security)

1. Key pair
2. Network settings
   • VPC
   • Subnet
     • Public subnet
     • Private subnet
   • Availability Zone
     • Select AZ
   • Auto-assign public IP
     • Enable(Pulbic EC2)
     • Disable(Private EC2)
   • Firewall (security groups)
   • Inbound Security Group Rules

3-6. Step 3. Set Environments (Storage)

1. Storage

3-7. Launch Instance

3-8. Confirm Instance

3-9. Start/Stop/Reboot/Terminate Instance

4. Related Concepts

• Automatically Management
  • Load Balancing
  • Target Groups
  • Auto Scaling Groups
• Storage
  • Elastic Block Store(ELB)
  • Snapshots
• Images
  • AMIs

• Template

• Networks
  • Elastic IPs