AWS Cloudformation Ec2 Agent Skill

AWS CloudFormation EC2 Infrastructure

Overview

Create production-ready EC2 infrastructure using AWS CloudFormation templates. Covers EC2 instances (On-Demand and SPOT), Security Groups, IAM roles, Application Load Balancers (ALB), template structure, parameters, outputs, and cross-stack references.

When to Use

• Creating EC2 instances (On-Demand or SPOT) with Security Groups and IAM roles
• Setting up Application Load Balancers with target groups
• Implementing template Parameters, Mappings, Conditions, and cross-stack references

Instructions

Step 1 — Define Template Parameters

Use AWS-specific parameter types for validation and console dropdowns.

Parameters:
  LatestAmiId:
    Type: AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>
    Default: /aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2

  InstanceType:
    Type: AWS::EC2::InstanceType
    Default: t3.micro
    AllowedValues: [t3.micro, t3.small, t3.medium]

  KeyName:
    Type: AWS::EC2::KeyPair::KeyName

See template-structure.md for advanced parameter patterns, mappings, conditions, and cross-stack references.

Step 2 — Create Security Group

Define ingress/egress rules for network access.

InstanceSecurityGroup:
  Type: AWS::EC2::SecurityGroup
  Properties:
    GroupDescription: Security group for EC2 instance
    VpcId: !Ref VpcId
    SecurityGroupIngress:
      - IpProtocol: tcp
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
      - IpProtocol: tcp
        FromPort: 22
        ToPort: 22
        CidrIp: 10.0.0.0/16

See security-iam.md for advanced security group patterns, self-references, and IAM roles.

Step 3 — Configure IAM Role

Define instance profile with least privilege permissions.

Ec2Role:
  Type: AWS::IAM::Role
  Properties:
    AssumeRolePolicyDocument:
      Version: "2012-10-17"
      Statement:
        - Effect: Allow
          Principal:
            Service: ec2.amazonaws.com
          Action: sts:AssumeRole
    ManagedPolicyArns:
      - arn:aws:iam::aws:policy/AmazonSSMManagedInstanceCore

Ec2InstanceProfile:
  Type: AWS::IAM::InstanceProfile
  Properties:
    Roles: [!Ref Ec2Role]

See security-iam.md for least privilege policies, SSM roles, and trust policies.

Step 4 — Launch EC2 Instance

Configure instance with security group, IAM role, and user data.

Ec2Instance:
  Type: AWS::EC2::Instance
  Properties:
    ImageId: !Ref LatestAmiId
    InstanceType: !Ref InstanceType
    KeyName: !Ref KeyName
    SecurityGroupIds: [!Ref InstanceSecurityGroup]
    IamInstanceProfile: !Ref Ec2InstanceProfile
    SubnetId: !Ref SubnetId
    UserData:
      Fn::Base64: |
        #!/bin/bash
        yum update -y
        yum install -y httpd
        systemctl start httpd
    Tags:
      - Key: Name
        Value: !Sub ${AWS::StackName}-instance

See ec2-instances.md for multi-volume configurations, detailed monitoring, SPOT instances, and complete stack examples.

Validate template: aws cloudformation validate-template --template-body file://template.yaml

Step 5 — Add Application Load Balancer

Create ALB with target group and listener for traffic distribution.

ApplicationLoadBalancer:
  Type: AWS::ElasticLoadBalancingV2::LoadBalancer
  Properties:
    Name: !Sub ${AWS::StackName}-alb
    Scheme: internet-facing
    SecurityGroups: [!Ref AlbSecurityGroup]
    Subnets: [!Ref PublicSubnet1, !Ref PublicSubnet2]

ApplicationTargetGroup:
  Type: AWS::ElasticLoadBalancingV2::TargetGroup
  Properties:
    Port: 80
    Protocol: HTTP
    VpcId: !Ref VpcId
    HealthCheckPath: /health

ApplicationListener:
  Type: AWS::ElasticLoadBalancingV2::Listener
  Properties:
    DefaultActions:
      - Type: forward
        TargetGroupArn: !Ref ApplicationTargetGroup
    LoadBalancerArn: !Ref ApplicationLoadBalancer
    Port: 80
    Protocol: HTTP

See load-balancers.md for HTTPS configuration, path-based routing, host-based routing, listener rules, and ALB attributes.

Step 6 — Define Outputs

Export values for cross-stack references.

Outputs:
  InstanceId:
    Description: EC2 Instance ID
    Value: !Ref Ec2Instance
    Export:
      Name: !Sub ${AWS::StackName}-InstanceId

  SecurityGroupId:
    Description: Security Group ID
    Value: !Ref InstanceSecurityGroup
    Export:
      Name: !Sub ${AWS::StackName}-SecurityGroupId

  LoadBalancerDnsName:
    Description: ALB DNS Name
    Value: !GetAtt ApplicationLoadBalancer.DNSName

See template-structure.md for cross-stack reference patterns and import/export strategies.

Examples

Minimal EC2 with ALB Template

AWSTemplateFormatVersion: "2010-09-09"
Description: EC2 instance with ALB

Parameters:
  LatestAmiId:
    Type: AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>
    Default: /aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2
  InstanceType:
    Type: AWS::EC2::InstanceType
    Default: t3.micro

Resources:
  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Enable HTTP and SSH
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0

  Ec2Instance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: !Ref LatestAmiId
      InstanceType: !Ref InstanceType
      SecurityGroupIds: [!Ref InstanceSecurityGroup]

  LoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Scheme: internet-facing
      SecurityGroups: [!Ref InstanceSecurityGroup]
      Subnets: [subnet-12345678, subnet-87654321]

Outputs:
  InstanceId:
    Value: !Ref Ec2Instance
  LoadBalancerDns:
    Value: !GetAtt LoadBalancer.DNSName

Deploy with Change Set

# Create change set
aws cloudformation create-change-set \
  --stack-name my-ec2-stack \
  --template-body file://template.yaml \
  --change-set-type CREATE

# Execute after review
aws cloudformation execute-change-set \
  --change-set-name <change-set-name>

See examples.md for complete production-ready templates.

Best Practices

Template Structure

• Use AWS-specific parameter types for validation (AWS::EC2::VPC::Id, AWS::EC2::InstanceType)
• Organize by lifecycle - separate network, security, and application stacks
• Use meaningful names with AWS::StackName prefix
• Enable termination protection on production stacks

Security

• Apply least privilege to IAM roles - grant minimum required permissions
• Use security group references instead of IP addresses where possible
• Enable IMDSv2 on all EC2 instances
• Restrict security group rules to specific CIDR blocks

Cost & Availability

• Use SPOT instances for fault-tolerant, interruptible workloads
• Deploy across multiple AZs for high availability
• Set up CloudWatch alarms for CPU and status checks
• Use EBS gp3 volumes for cost-effective storage

Operations

• Always use change sets for production stack updates
• Enable drift detection to maintain template compliance
• Apply stack policies to protect critical resources
• Validate templates before deployment with aws cloudformation validate-template

See best-practices.md for detailed guidance on stack policies, termination protection, drift detection, change set automation, and validation scripts.

References

Core Configuration

• template-structure.md — Template sections, parameters, mappings, conditions, outputs, cross-stack references
• ec2-instances.md — EC2 instances, SPOT fleets, multi-volume configurations, complete stack examples
• security-iam.md — Security groups, IAM roles, instance profiles, least privilege policies
• load-balancers.md — ALB configuration, target groups, listeners, path-based routing, HTTPS

Operational Guides

• best-practices.md — Stack policies, termination protection, drift detection, change sets, validation
• constraints.md — Resource limits, instance constraints, cost considerations, common issues, monitoring

Additional Resources

• examples.md — Complete production-ready examples and use cases
• reference.md — CloudFormation EC2 resource reference documentation

Constraints and Warnings

Resource Limits

• Maximum 500 resources per CloudFormation stack
• Maximum 500 security groups per VPC
• Instance types vary by region/A availability

Cost Considerations

• EC2 instances incur costs while running
• EBS volumes charged per GB-month even when not attached
• ALBs have hourly + LCU data processing costs
• Unattached Elastic IPs incur hourly costs

Security Considerations

• Key pairs cannot be recovered if lost
• Instance profile roles cannot be changed after creation
• IMDSv1 has security vulnerabilities - use IMDSv2
• Spot instances can be terminated with 2-minute notice

See constraints.md for complete constraints, troubleshooting guides, and monitoring setup.