Template format error: Unresolved resource dependencies [subnet-057ba3df40f87da4e] in the Resources-CodePudding

I'm trying to create an EC2 instance in a VPC using cloudformation, when I run the following:

aws cloudformation create-stack --stack-name stack --region us-east-1 --template-body file://file.yml

I get the following error:

An error occurred (ValidationError) when calling the CreateStack operation:
Template format error: Unresolved resource dependencies [subnet-057ba3df40f87da4e] 
in the Resources block of the template

known that this is the yaml file I'm using to create this stack:

Resources:

  accessSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties: 
      GroupDescription: "new EC2 security group for HTTP and SHH ports"
      SecurityGroupIngress: 
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0
      SecurityGroupEgress:
        - IpProtocol: -1
          FromPort: -1
          ToPort: -1
          CidrIp: 0.0.0.0/0
      VpcId: "vpc-09495a820716bff3b"
  
  EC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: "ami-0022f774911c1d690"
      InstanceType: t3.micro
      NetworkInterfaces: 
        - AssociatePublicIpAddress: "true"
          DeviceIndex: "0"
          GroupSet: 
            - Ref: "accessSecurityGroup"
          SubnetId: 
            Ref: "subnet-057ba3df40f87da4e"
      UserData:
        Fn::Base64: 
          !Sub |
            #!/bin/bash
            sudo yum update -y
            sudo yum install -y httpd
            sudo systemctl start httpd
            sudo systemctl enable httpd 
      SecurityGroupIds:
        - !Ref accessSecurityGroup

I'm positive that the above VpcId, and SubnetId exist, and I'm not sure what seems to be the problem.

CodePudding user response：

The intrinsic function Ref returns the value of the specified parameter or resource. Drop Ref since it's not referring to a parameter or resource, and the value is hardcoded

SubnetId: "subnet-057ba3df40f87da4e"

Recommend trying the CloudFormation Linter in VSCode to see these errors inline while authoring templates along with autocompletion and documentation links:

E1012 Ref subnet-057ba3df40f87da4e not found as a resource or parameter