A sample CloudFormation template integrating cloud-init and cfn-signal

cloud-init-and-cfn-signal.yaml

---
AWSTemplateFormatVersion: '2010-09-09'
Description: cloud-init and cfn-signal
Parameters:
  SubnetId:
    Type: AWS::EC2::Subnet::Id
    Description: The subnet to deploy the instance in
    Default: "subnet-026f62073564ba8fe"
  AL2023:
    Type: 'AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>'
    Default: /aws/service/ami-amazon-linux-latest/al2023-ami-kernel-6.1-x86_64
    Description: Latest Amazon Linux 2023 AMI from SSM
  ExitCode:
    Type: Number
    MinValue: 0
    MaxValue: 255
    Default: 0

Resources:
  AutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      AutoScalingGroupName: Demo
      LaunchTemplate:
        LaunchTemplateId: !Ref 'LaunchTemplate'
        Version: !GetAtt 'LaunchTemplate.LatestVersionNumber'
      MinSize: '1'
      MaxSize: '2'
      DesiredCapacity: '1'
      VPCZoneIdentifier:
        - !Ref SubnetId
    UpdatePolicy:
      AutoScalingRollingUpdate:
        MinInstancesInService: 1
        MaxBatchSize: 10
        WaitOnResourceSignals: true
    CreationPolicy:
      ResourceSignal:
        Count: 1
        Timeout: PT5M

  LaunchTemplate:
    Type: AWS::EC2::LaunchTemplate
    Properties:
      LaunchTemplateName: SampleTemplate
      LaunchTemplateData:
        ImageId: !Ref AL2023
        InstanceType: t3.micro
        IamInstanceProfile:
          Arn: !GetAtt InstanceProfile.Arn
        UserData: !Base64
          Fn::Sub: |
            #cloud-config
            write_files:
              - path: /etc/systemd/system/cfn-signal.service
                permissions: '0644'
                content: |
                  # 
                  # When cloud-init completed successfully, report this to CFN     
                  # using cfn-signal
                  #   
                  [Unit]
                  Description=Signal completion of cloud-init to CFN
                  Wants=cloud-init.target
                  After=cloud-init.target        
                
                  [Service]
                  Type=oneshot
                  ExecStart=/bin/bash -c '\
                      cloud-init status --wait | grep -q "^status: done$"; \
                      /opt/aws/bin/cfn-signal \
                          --stack "$STACK_NAME" \
                          --resource "$LOGICAL_RESOURCE_ID" \
                          --region "$AWS_REGION" \
                          --exit-code $? \
                  '
            
                  [Install]
                  WantedBy=default.target

              - path: /etc/systemd/system/cfn-signal.service.d/override.conf
                permissions: '0644'
                content: |
                  [Service]
                  Environment="AWS_REGION=${AWS::Region}"
                  Environment="STACK_NAME=${AWS::StackName}"
                  Environment="LOGICAL_RESOURCE_ID=AutoScalingGroup"

            runcmd:
              - sudo systemctl daemon-reload
              - sudo systemctl enable --now --no-block cfn-signal
              - exit ${ExitCode}

  SSMRole:
    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

  InstanceProfile:
    Type: AWS::IAM::InstanceProfile
    Properties:
      Roles:
        - !Ref SSMRole