How to reference a resource created by a Terraform module

Question

I'm using the AWS VPC Terraform module to create a VPC. Additionally, I want to create and attach an Internet Gateway to this VPC using the aws_internet_gateway resource.

Here is my code:

module "vpc" "vpc_default" {   source = "terraform-aws-modules/vpc/aws"    name = "${var.env_name}-vpc-default"   cidr = "10.0.0.0/16"   enable_dns_hostnames = true }  resource "aws_internet_gateway" "vpc_default_igw" {   vpc_id = "${vpc.vpc_default.id}"    tags {     Name = "${var.env_name}-vpc-igw-vpcDefault"   } } 

When I run terraform init, I get the following error:

Initializing modules... - module.vpc

Error: resource 'aws_internet_gateway.vpc_default_igw' config: unknown resource 'vpc.vpc_default' referenced in variable vpc.vpc_default.id

How can I reference a resource created by a Terraform module?

Answer 1

Since you're using a module, you need to change the format of the reference slightly. Module Outputs use the form ${module.<module name>.<output name>}. It's also important to note, you can only reference values outputted from a module.

In your specific case, this would become ${module.vpc.vpc_id} based on the VPC Module's Outputs.