Understanding Amazon EC2 (Elastic Compute Cloud)

Amazon EC2 is the foundation of AWS compute services—used by startups, enterprises, and developers globally. This chapter explores EC2 in depth: what it is, how it works, its pricing, and how to launch and manage EC2 instances.

What is Amazon EC2?

Amazon EC2 (Elastic Compute Cloud) is a web service that provides resizable, scalable compute capacity in the cloud. Think of EC2 as a virtual server (VM) that you can launch, configure, stop, restart, or terminate as needed.

📌 EC2 allows businesses to run applications without upfront hardware investment and supports Linux/Unix and Windows platforms.

EC2 Key Components

Term	Description
Instance	A virtual server in AWS
AMI (Amazon Machine Image)	A template with OS + software to launch an instance
Instance Type	Defines hardware (CPU, RAM, etc.) resources
Security Group	Acts as a virtual firewall
Key Pair	SSH authentication mechanism
Elastic IP	Static IP address for an instance
EBS Volume	Storage attached to the instance

EC2 Instance Types

AWS provides a wide variety of instance families, each optimized for different use cases.

Family	Use Case	Examples
General Purpose	Balanced CPU/RAM	t2.micro, t3.medium
Compute Optimized	High-performance CPU	c5.large, c6g.xlarge
Memory Optimized	RAM-heavy apps	r5.large, x1e.xlarge
Storage Optimized	Fast IOPS	i3.large, d2.xlarge
GPU Instances	ML, AI, Graphics	p3.2xlarge, g4dn

Step-by-Step: Launching an EC2 Instance

1. Go to EC2 Dashboard

Choose your region
Click Launch Instance

2. Select an AMI

Use Amazon Linux 2, Ubuntu, Windows Server, etc.

3. Choose Instance Type

Select t2.micro for Free Tier

4. Configure Instance

Default values for testing are okay
For production: setup subnets, roles, shutdown behavior

5. Add Storage

Default: 8 GB General Purpose SSD (gp2)

6. Configure Security Group

Allow port 22 (SSH) for Linux
Allow port 3389 for Windows (RDP)
Add HTTP/HTTPS (port 80/443) for web apps

7. Review and Launch

Select/Create Key Pair (.pem) for SSH
Click Launch

🔑 Connecting to EC2 (Linux)

Bash

ssh -i "your-key.pem" ec2-user@<Public-IP>

ssh -i "your-key.pem" ec2-user@<Public-IP>

🔐 Always secure your .pem file, and set permissions with chmod 400 your-key.pem.

🧯 Managing EC2 Instances

You can Start, Stop, Reboot, or Terminate instances anytime from the EC2 Dashboard.

Action	Effect
Stop	Shuts down the VM but retains data
Terminate	Deletes the VM and attached storage (unless preserved)
Reboot	Restarts the VM
Elastic IP	Associates a public static IP

EC2 Pricing Models

Model	Description	Ideal For
On-Demand	Pay per second/minute	Short-term workloads
Reserved Instances	1 or 3-year commitment for lower cost	Predictable usage
Spot Instances	Bid for unused capacity (up to 90% off)	Fault-tolerant, flexible apps
Savings Plans	Flexible pricing for consistent usage	Cost-optimization

EC2 Auto Scaling

With Auto Scaling, AWS automatically adjusts the number of EC2 instances based on traffic load or performance metrics.

Create Launch Templates
Define Scaling Policies
Integrate with Elastic Load Balancer (ELB)

Security Best Practices for EC2

Always use SSH key pairs
Use IAM roles for instance-level access (e.g., access S3 securely)
Regularly update OS packages
Enable CloudWatch monitoring
Use Elastic IP sparingly to avoid cost
Open only required ports in the security group

📌 Summary

Concept	Summary
What is EC2	Virtual server in AWS
AMI & Instance Type	OS template & hardware configuration
Launching Instance	7-step process via Console
Connection Method	SSH or RDP
Pricing Models	On-Demand, Reserved, Spot, Savings Plans
Auto Scaling	Automatically handle traffic/load
Security Practices	Key pairs, IAM roles, security groups

📘 Continue to the Next Chapter

Understanding AWS Global Infrastructure

Learn how AWS regions, availability zones, and edge locations form the backbone of cloud scalability and resilience.

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💡 Explore More AWS Tools & Resources

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