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terraform

Terraform: how to access a resource in module for output?

How to access a resource for output, for exampe ec2 instance: aws_instance.splat_lab.ebs_block_device.*.volume_id Tried notation module.module-name.path-to-resource, i.e. module.webserver-cas12.aws_instance.splat_lab.ebs_block_device.*.volume_id but module.module-name is empty.

How to output from module or how to inbuild output of a speciific resource to module?

Solution

  • To properly output a specific resource, like an EC2 instance's volume_id, from a module in Terraform, here are some things you need to check:

    First, make sure the module itself defines the output you need. You can define the output for the volume_id in the outputs.tf file within the module.

    output "ebs_volume_ids" {
  value = aws_instance.splat_lab.ebs_block_device.*.volume_id
}

    This will output all the volume_ids associated with the ebs_block_device of the EC2 instance resource inside the module.

    In your root module (where you call the module), you can reference this output using the following syntax:

    module "webserver" {
  source = "./path-to-your-module"

  # Other variables you may pass to the module
}

output "webserver_ebs_volume_ids" {
  value = module.webserver.ebs_volume_ids
}

    Make sure the module name (webserver) matches the name you use in your module block.

    Notes based on your specific situation:

    • If module.webserver is empty, ensure that the module's source is defined properly, and that the module is correctly pulling the resources you expect.
    • Terraform modules encapsulate resources, so you need to define outputs explicitly to access the internal resource attributes like volume_id.
    • To confirm the resource exists within the module, use terraform plan or terraform state list to inspect the state and see if the resource is being created as expected.