Terraform Modules - Unable to Access variable from root - terraform

Question

I am trying to pass a variable from the root module to a child module with the following syntax and i'm unable to do that:
└── Terraform
├── main.tf
├── variable.tf
└── module
├──main.tf
├── variable.tf
Terraform Version:
Terraform v0.11.11
+ provider.openstack v1.15.0
Terraform Configuration Files
/Terraform/main.tf:
provider "openstack" {
openstack_user_name = "${var.openstack_user_name}"
openstack_tenant_name = "${var.openstack_tenant_name}"
openstack_password = "${var.openstack_password}"
openstack_auth_url = "${var.openstack_auth_url}"
domain_name = "${var.domain_name}"
}
module "testMod" {
name = "${var.name}"
imageId = "${var.imageId}"
flavor_name = "${var.flavor_name}"
openstack_keypair = "${var.openstack_keypair}"
tenant_network_id = "${var.tenant_network_id}"
tenant_network = "${var.tenant_network}"
source = "./modules"
}
/Terraform/variable.tf:
variable "name" {default = "XXX"}
variable "imageId" {default = "11-22-33"}
variable "flavor_name"{default = "flavor"}
...
/Terraform/modules/main.tf:
resource "openstack_compute_instance_v2" "test" {
name = "${var.name}"
imageId = "${var.imageId}"
flavor_name = "${var.flavor_name}"
openstack_keypair = "${var.openstack_keypair}"
security_groups = ["default"]
network {
tenant_network_id = "${var.tenant_network_id}"
tenant_network = "${var.tenant_network}"
}
}
/Terraform/modules/variable.tf:
variable "name" {}
variable "imageId" {}
variable "flavor_name" {}
variable "openstack_keypair" {}
variable "tenant_network_id"{}
variable "tenant_network" {}
Actual Behavior
Error: module.testMod.openstack_compute_instance_v2.test: : invalid or unknown key: imageId
Steps to Reproduce
terraform init
terraform apply
Unsure what is going wrong here

Answer 1

The error is alerting you to the unknown keyimageId. This message is accurate as, in fact, the key should be image_id. You can check the Terraform openstack_compute_instance_v2 resource documentation and note the presence of the image_id argument.
Your code would then look like:
resource "openstack_compute_instance_v2" "test" {
name = "${var.name}"
image_id = "${var.imageId}"
flavor_name = "${var.flavor_name}"
openstack_keypair = "${var.openstack_keypair}"
security_groups = ["default"]
}

Answer 2

I have this requirement to access variables from root variable.tf inside module/myservice/main.tf
How can we achive that ? By using var.environmentdoes not work
e.g:
root/variable.tf
variable "environment" {
type = string
description = "Resource environment e.g dev, test or prod."
default = "dev"
}
How to access above variable var.environment in root/module/myservice/main.tf using ${var.environment} does not work.
root/module/myservice/main.tf
locals {
name = "${var.environment}.myInstance"
}
resource "aws_network_interface" "foo" {
name = local.name
.
.
.
}