terraform - Difference between "Importing into module" and "Importing into resource" in terraforn

Question

I was reading Terraform's docs and I found these two commands:

• Import into resource

$ terraform import aws_instance.foo i-abcd1234

• Import into module

$ terraform import module.foo.aws_instance.bar i-abcd1234

So I was wondering what's the practical difference within terraform's state when you execute these two commands.

Thanks in advance!

question from:https://stackoverflow.com/questions/65879110/difference-between-importing-into-module-and-importing-into-resource-in-terr

Answer 1

When running terrafom import Terraform expects the resources you're importing to to be defined in your configuration.

For your first case $ terraform import aws_instance.foo i-abcd1234 you would need to define at least:

# main.tf
resource "aws_instance" "foo" {
}

Terraform will update the statefile with details from AWS.

In the second one $ terraform import module.foo.aws_instance.bar i-abcd1234 Terraform expects module 'foo' containing resource 'aws_instance bar' to exist. Check on when to create modules and how to compose them. E.g.

# modules/foo
resource "aws_instance" "foo" {
}

# main.tf
module "consul_cluster" {
  source = "./modules/aws-consul-cluster"
}

If you will check the statefile you'll see that your imported resource is nested differently.