aws-cloudformation-ec2

# 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.

```yaml
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](references/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.

```yaml
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](references/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.

```yaml
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](references/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.

```yaml
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](references/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.

```yaml
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](references/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.

```yaml
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](references/template-structure.md) for cross-stack reference patterns and import/export strategies.

## Examples

### Minimal EC2 with ALB Template

```yaml
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

```bash
# Create change set
aws c