Amazon EC2 Essentials

Amazon EC2 (Elastic Compute Cloud) is AWS's virtual computing service that lets you launch and manage virtual servers (instances) in the cloud.

The problem it solves: It eliminates the need to purchase, configure, and maintain physical hardware to run applications. It provides scalable, on-demand compute capacity.

When to use it:

• You need full control over the operating system and configuration
• Apps that require persistent resources (web servers, databases, workers)
• Predictable workloads or those requiring dedicated instances

Alternatives:

• Lambda: For serverless code without server management
• ECS/Fargate: For containers without managing infrastructure
• Lightsail: For simple cases with predefined configuration

Key Concepts

Essential AWS CLI Commands

Creating Resources

# Create keypair
aws ec2 create-key-pair \
  --key-name my-keypair \
  --query 'KeyMaterial' \
  --output text > my-keypair.pem

chmod 400 my-keypair.pem  # Adjust permissions

# Create security group
aws ec2 create-security-group \
  --group-name web-server-sg \
  --description "Allow HTTP and SSH" \
  --vpc-id vpc-xxxxxx

# Add rules to security group
aws ec2 authorize-security-group-ingress \
  --group-id sg-xxxxx \
  --protocol tcp \
  --port 22 \
  --cidr 157.100.121.171/32  # Your specific IP

# Launch instance
aws ec2 run-instances \
  --image-id ami-0da00c97ce64145f1 \
  --instance-type t3.micro \
  --key-name my-keypair \
  --security-group-ids sg-xxxxx \
  --user-data file://userdata.sh \
  --tag-specifications 'ResourceType=instance,Tags=[{Key=Name,Value=WebServer-01}]'

# Allocate Elastic IP
aws ec2 allocate-address

Querying Resources

# Verify identity (pre-flight)
aws sts get-caller-identity

# List VPCs (find default VPC)
aws ec2 describe-vpcs \
  --query 'Vpcs[?IsDefault==`true`].VpcId' \
  --output text

# Find most recent AMI
aws ec2 describe-images \
  --owners amazon \
  --filters "Name=name,Values=al2023-ami-2023*" \
            "Name=architecture,Values=x86_64" \
  --query 'sort_by(Images, &CreationDate)[-1].ImageId' \
  --output text

# Check instance state
aws ec2 describe-instances \
  --instance-ids i-xxxxx \
  --query 'Reservations[0].Instances[0].[State.Name,PublicIpAddress]' \
  --output table

# Detailed status checks
aws ec2 describe-instance-status \
  --instance-ids i-xxxxx

# View applied security group
aws ec2 describe-security-groups \
  --group-ids sg-xxxxx

# View EBS volumes
aws ec2 describe-volumes \
  --volume-ids vol-xxxxx

# Console output (debugging)
aws ec2 get-console-output \
  --instance-id i-xxxxx \
  --output text > console-output.txt

# List Elastic IPs
aws ec2 describe-addresses

Modifying Resources

# Modify instance attribute
aws ec2 modify-instance-attribute \
  --instance-id i-xxxxx \
  --instance-type t3.small

# Change volume DeleteOnTermination
aws ec2 modify-instance-attribute \
  --instance-id i-xxxxx \
  --block-device-mappings DeviceName=/dev/xvda,Ebs={DeleteOnTermination=false}

Deleting Resources

# Terminate instance
aws ec2 terminate-instances \
  --instance-ids i-xxxxx

# Delete security group
aws ec2 delete-security-group \
  --group-id sg-xxxxx

# Release Elastic IP
aws ec2 release-address \
  --allocation-id eipalloc-xxxxx

# Delete keypair
aws ec2 delete-key-pair \
  --key-name my-keypair

Architecture and Flows

EC2 Instance Components

Instance Launch Flow

EBS Lifecycle

Best Practices Checklist

Security

• Never expose port 22 to 0.0.0.0/0 - use specific IP or Session Manager
• Use security groups with least privilege principle
• Rotate keypairs periodically and store them securely
• Enable encryption on EBS volumes (Encrypted: true)
• Use IAM roles instead of hardcoding credentials on instances
• Keep OS updated (yum update -y in user data)

Cost Optimization

• Set DeleteOnTermination: true for ephemeral instances
• Release Elastic IPs that aren't in use
• Monitor CPU Credits on T instances - consider M family if constantly bursting
• Use appropriate sizes - start small and scale based on metrics
• Consider Reserved Instances or Savings Plans for predictable workloads
• Terminate development instances outside business hours

Performance

• Choose instance type based on the real bottleneck (CPU vs RAM vs I/O)
• Use gp3 instead of gp2 for better cost/performance
• For I/O intensive workloads, consider Instance Store or io2 EBS
• Launch instances in Availability Zone close to users
• Enable detailed monitoring if you need metrics every 1 min

Reliability

• Never use a single instance in production - design for multiple AZs
• Implement proper health checks
• Automate deployments with user data or config management
• Create AMIs from configured instances for quick recovery
• Configure automated snapshots for critical EBS volumes

Operational Excellence

• Use consistent tags (Name, Environment, Project, Owner)
• Document in user data what's installed and why
• Use CloudWatch for centralized logs
• Implement Infrastructure as Code (CloudFormation/Terraform)
• Maintain inventory of instances and their purposes

Common Mistakes to Avoid

# Test 1: Can you reach port 80?
curl http://[instance-ip]  # If it works, it's not AWS

# Test 2: Specifically verify SSH
nc -zv [instance-ip] 22    # If timeout, local network issue

chmod 400 my-keypair.pem  # Always after creating keypair

# List orphaned EIPs
aws ec2 describe-addresses \
  --query 'Addresses[?AssociationId==null]'

# Release immediately if not in use
aws ec2 release-address --allocation-id eipalloc-xxxxx

# Always check detailed status checks
aws ec2 describe-instance-status --instance-ids i-xxxxx

Cost Considerations

What generates costs in EC2

Cost Optimization

Free Tier (first 12 months):

• 750 hours/month of t2.micro or t3.micro (Linux)
• 30 GB of EBS General Purpose (gp2 or gp3)
• 1 GB of snapshots

Strategies:

1. Right-sizing: Start with t3.micro, scale based on CloudWatch metrics
2. Stop vs Terminate: For dev/test, stop when not in use (you don't pay for instance, only EBS)
3. Spot Instances: 70-90% discount for fault-tolerant workloads (not covered yet)
4. Reserved/Savings Plans: Up to 72% discount for predictable workloads (not covered yet)

Monitoring:

# View costs by instance type
aws ce get-cost-and-usage \
  --time-period Start=2025-10-01,End=2025-10-10 \
  --granularity DAILY \
  --metrics UnblendedCost \
  --group-by Type=DIMENSION,Key=INSTANCE_TYPE

Integration with Other Services

Additional Resources

Official Documentation

• EC2 User Guide
• EC2 Instance Types
• EBS Documentation
• T Instance CPU Credits

Whitepapers

• AWS Well-Architected Framework
• Cost Optimization Pillar

Tools

• EC2 Instance Comparison
• AWS Pricing Calculator