Create EC2 in default public subnet only using cloudformation - amazon-web-services

Question

I have CF template which is creating EC2 machine.
AWSTemplateFormatVersion: 2010-09-09
Mappings:
InstanceAMI:
# ubuntu 18.04
us-west-2:
ami: 'ami-0bbe6b35405ecebdb'
us-east-1:
ami: 'ami-0ac019f4fcb7cb7e6'
Parameters:
Endpoint:
Type: String
# TODO edit the default value
Description:
Resources:
NodeInstanceProfile:
Type: AWS::IAM::InstanceProfile
Properties:
Path: "/"
Roles:
- !Ref NodeInstanceRole
NodeInstanceRole:
Type: AWS::IAM::Role
Properties:
AssumeRolePolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Principal:
Service:
- ec2.amazonaws.com
Action:
- sts:AssumeRole
Path: "/"
ManagedPolicyArns:
- arn:aws:iam::aws:policy/AdministratorAccess
CdpDeplSvcSecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: Access Deployment service
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: 443
ToPort: 443
CidrIp: 0.0.0.0/0
- IpProtocol: tcp
FromPort: 8080
ToPort: 8080
CidrIp: 0.0.0.0/0
- IpProtocol: tcp
FromPort: 22
ToPort: 22
CidrIp: 0.0.0.0/0
Tags:
- Key: Name
Value: 'Access Deployment'
DeploymentMachine:
Type: AWS::EC2::Instance
Properties:
# AvailabilityZone: us-east-1a
ImageId: !FindInMap [InstanceAMI, !Ref "AWS::Region", ami]
InstanceType: 't2.small'
KeyName: 'key'
Tags:
- Key: Name
Value: 'Deployment'
BlockDeviceMappings:
- DeviceName: "/dev/sda1"
Ebs:
# VolumeType: "io1"
# Iops: "200"
DeleteOnTermination: "true"
VolumeSize: "30"
NetworkInterfaces:
- DeviceIndex: 0
AssociatePublicIpAddress: 'true'
DeleteOnTermination: 'true'
GroupSet:
- !GetAtt CdpDeplSvcSecurityGroup.GroupId
IamInstanceProfile: !Ref NodeInstanceProfile
It executing correctly. But the problem I am facing is sometimes it creates in default private subnet, sometimes in default public subnet.
I want to deploy this machine in the default public subnet only. I don't want to pass VPC id or subnet id as parameter. For that, what I have change here.

Answer 1

This will just put it into a random subnet - you need to hardcode subnet, or specify subnet through a parameter and then reference the parameter - this can provide you with some flexibility for varying the subnet per customer.
Potentially, during deployment of your stack, you could script the deployment, using the AWS CLI to get all public subnets, and pass one in as a parameter into your cloudformation stack.