Agent Skills: AWS EC2

AWS EC2

Amazon Elastic Compute Cloud (EC2) provides resizable compute capacity in the cloud. Launch virtual servers, configure networking and security, and manage storage.

Table of Contents

• Core Concepts
• Common Patterns
• CLI Reference
• Best Practices
• Troubleshooting
• References

Core Concepts

Instance Types

| Category | Example | Use Case | |----------|---------|----------| | General Purpose | t3, m6i | Web servers, dev environments | | Compute Optimized | c6i | Batch processing, gaming | | Memory Optimized | r6i | Databases, caching | | Storage Optimized | i3, d3 | Data warehousing | | Accelerated | p4d, g5 | ML, graphics |

Purchasing Options

| Option | Description | |--------|-------------| | On-Demand | Pay by the hour/second | | Reserved | 1-3 year commitment, up to 72% discount | | Spot | Unused capacity, up to 90% discount | | Savings Plans | Flexible commitment-based discount |

AMI (Amazon Machine Image)

Template containing OS, software, and configuration for launching instances.

Security Groups

Virtual firewalls controlling inbound and outbound traffic.

Common Patterns

Launch an Instance

AWS CLI:

# Create key pair
aws ec2 create-key-pair \
  --key-name my-key \
  --query 'KeyMaterial' \
  --output text > my-key.pem
chmod 400 my-key.pem

# Create security group
aws ec2 create-security-group \
  --group-name web-server-sg \
  --description "Web server security group" \
  --vpc-id vpc-12345678

# Allow SSH and HTTP
aws ec2 authorize-security-group-ingress \
  --group-id sg-12345678 \
  --protocol tcp \
  --port 22 \
  --cidr 10.0.0.0/8

aws ec2 authorize-security-group-ingress \
  --group-id sg-12345678 \
  --protocol tcp \
  --port 80 \
  --cidr 0.0.0.0/0

# Launch instance
aws ec2 run-instances \
  --image-id ami-0123456789abcdef0 \
  --instance-type t3.micro \
  --key-name my-key \
  --security-group-ids sg-12345678 \
  --subnet-id subnet-12345678 \
  --tag-specifications 'ResourceType=instance,Tags=[{Key=Name,Value=web-server}]'

boto3:

import boto3

ec2 = boto3.resource('ec2')

instances = ec2.create_instances(
    ImageId='ami-0123456789abcdef0',
    InstanceType='t3.micro',
    KeyName='my-key',
    SecurityGroupIds=['sg-12345678'],
    SubnetId='subnet-12345678',
    MinCount=1,
    MaxCount=1,
    TagSpecifications=[{
        'ResourceType': 'instance',
        'Tags': [{'Key': 'Name', 'Value': 'web-server'}]
    }]
)

instance = instances[0]
instance.wait_until_running()
instance.reload()
print(f"Instance ID: {instance.id}")
print(f"Public IP: {instance.public_ip_address}")

User Data Script

aws ec2 run-instances \
  --image-id ami-0123456789abcdef0 \
  --instance-type t3.micro \
  --key-name my-key \
  --security-group-ids sg-12345678 \
  --subnet-id subnet-12345678 \
  --user-data '#!/bin/bash
    yum update -y
    yum install -y httpd
    systemctl start httpd
    systemctl enable httpd
    echo "<h1>Hello from $(hostname)</h1>" > /var/www/html/index.html
  '

Attach IAM Role

# Create instance profile
aws iam create-instance-profile \
  --instance-profile-name web-server-profile

aws iam add-role-to-instance-profile \
  --instance-profile-name web-server-profile \
  --role-name web-server-role

# Launch with profile
aws ec2 run-instances \
  --image-id ami-0123456789abcdef0 \
  --instance-type t3.micro \
  --iam-instance-profile Name=web-server-profile \
  ...

Create AMI from Instance

aws ec2 create-image \
  --instance-id i-1234567890abcdef0 \
  --name "my-custom-ami-$(date +%Y%m%d)" \
  --description "Custom AMI with web server" \
  --no-reboot

Spot Instance Request

aws ec2 request-spot-instances \
  --instance-count 1 \
  --type "one-time" \
  --launch-specification '{
    "ImageId": "ami-0123456789abcdef0",
    "InstanceType": "c5.large",
    "KeyName": "my-key",
    "SecurityGroupIds": ["sg-12345678"],
    "SubnetId": "subnet-12345678"
  }' \
  --spot-price "0.05"

EBS Volume Management

# Create volume
aws ec2 create-volume \
  --availability-zone us-east-1a \
  --size 100 \
  --volume-type gp3 \
  --iops 3000 \
  --throughput 125 \
  --encrypted

# Attach to instance
aws ec2 attach-volume \
  --volume-id vol-12345678 \
  --instance-id i-1234567890abcdef0 \
  --device /dev/sdf

# Create snapshot
aws ec2 create-snapshot \
  --volume-id vol-12345678 \
  --description "Daily backup"

CLI Reference

Instance Management

| Command | Description | |---------|-------------| | aws ec2 run-instances | Launch instances | | aws ec2 describe-instances | List instances | | aws ec2 start-instances | Start stopped instances | | aws ec2 stop-instances | Stop running instances | | aws ec2 reboot-instances | Reboot instances | | aws ec2 terminate-instances | Terminate instances | | aws ec2 modify-instance-attribute | Modify instance settings |

Security Groups

| Command | Description | |---------|-------------| | aws ec2 create-security-group | Create security group | | aws ec2 describe-security-groups | List security groups | | aws ec2 authorize-security-group-ingress | Add inbound rule | | aws ec2 revoke-security-group-ingress | Remove inbound rule | | aws ec2 authorize-security-group-egress | Add outbound rule |

AMIs

| Command | Description | |---------|-------------| | aws ec2 describe-images | List AMIs | | aws ec2 create-image | Create AMI from instance | | aws ec2 copy-image | Copy AMI to another region | | aws ec2 deregister-image | Delete AMI |

EBS Volumes

| Command | Description | |---------|-------------| | aws ec2 create-volume | Create EBS volume | | aws ec2 attach-volume | Attach to instance | | aws ec2 detach-volume | Detach from instance | | aws ec2 create-snapshot | Create snapshot | | aws ec2 modify-volume | Resize/modify volume |

Best Practices

Security

• Use IAM roles instead of access keys on instances
• Restrict security groups — principle of least privilege
• Use private subnets for backend instances
• Enable IMDSv2 to prevent SSRF attacks
• Encrypt EBS volumes at rest

# Require IMDSv2
aws ec2 modify-instance-metadata-options \
  --instance-id i-1234567890abcdef0 \
  --http-tokens required \
  --http-endpoint enabled

Performance

• Right-size instances — monitor and adjust
• Use EBS-optimized instances
• Choose appropriate EBS volume type
• Use placement groups for low-latency networking

Cost Optimization

• Use Spot Instances for fault-tolerant workloads
• Stop/terminate unused instances
• Use Reserved Instances for steady-state workloads
• Delete unused EBS volumes and snapshots

Reliability

• Use Auto Scaling Groups for high availability
• Deploy across multiple AZs
• Use Elastic Load Balancer for traffic distribution
• Implement health checks

Troubleshooting

Cannot SSH to Instance

Checklist:

1. Security group allows SSH (port 22) from your IP
2. Instance has public IP or use bastion/SSM
3. Key pair matches instance
4. Instance is running
5. Network ACL allows traffic

# Check security group
aws ec2 describe-security-groups --group-ids sg-12345678

# Check instance state
aws ec2 describe-instances \
  --instance-ids i-1234567890abcdef0 \
  --query "Reservations[].Instances[].{State:State.Name,PublicIP:PublicIpAddress}"

Use Session Manager instead:

aws ssm start-session --target i-1234567890abcdef0

Instance Won't Start

Causes:

• Reached instance limits
• Insufficient capacity in AZ
• EBS volume issue
• Invalid AMI

# Check instance state reason
aws ec2 describe-instances \
  --instance-ids i-1234567890abcdef0 \
  --query "Reservations[].Instances[].StateReason"

Instance Unreachable

Debug:

# Check instance status
aws ec2 describe-instance-status \
  --instance-ids i-1234567890abcdef0

# Get console output
aws ec2 get-console-output \
  --instance-id i-1234567890abcdef0

# Get screenshot (for Windows/GUI issues)
aws ec2 get-console-screenshot \
  --instance-id i-1234567890abcdef0

High CPU/Memory

# Enable detailed monitoring
aws ec2 monitor-instances \
  --instance-ids i-1234567890abcdef0

# Check CloudWatch metrics
aws cloudwatch get-metric-statistics \
  --namespace AWS/EC2 \
  --metric-name CPUUtilization \
  --dimensions Name=InstanceId,Value=i-1234567890abcdef0 \
  --start-time $(date -d '1 hour ago' -u +%Y-%m-%dT%H:%M:%SZ) \
  --end-time $(date -u +%Y-%m-%dT%H:%M:%SZ) \
  --period 300 \
  --statistics Average

References

• EC2 User Guide
• EC2 API Reference
• EC2 CLI Reference
• boto3 EC2