Trying to understand input variables - tfvars/

Terraform noob here. Quick question. We have a project where we have variables defined in at master · magma/magma · GitHub) and I’m trying to override the required variables by using tfvars file.

root@ac19040aa1c7:~/tf# terraform plan -target=module.orc8r -var-file="infra.tfvars.json"

Warning: Value for undeclared variable

The root module does not declare a variable named "orc8r_domain_name" but a
value was found in file "infra.tfvars.json". To use this value, add a
"variable" block to the configuration.

Using a variables file to set an undeclared variable is deprecated and will
become an error in a future release. If you wish to provide certain "global"
settings to all configurations in your organization, use TF_VAR_...
environment variables to set these instead.


Error: Missing required argument

  on line 19, in module "orc8r-app":
  19: module "orc8r-app" {

The argument "orc8r_domain_name" is required, but no definition was found.

I’m seeing both errors specifying that the variable I’m setting in tfvars json is an undeclared variable and the required variable in file is not defined.

What am i missing ? How should I properly assign the values to the required variables defined in file through tfvars file ?

Any pointers here would be greatly useful.


It sounds like you have a module that requires the “orc8r_domain_name” variable, but the module block in isn’t supplying it.

If you are wanting to use a tfvars file that is for passing in variables to the root module, so you’d need to create a variable block (normally in and then pass that into the module (orc8r_domain_name = var.orc8r_domain_name).

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Thanks for the quick response here. Do you know how we can pass tfvars directly to a specific module instead of passing it to root module.

Hi @karthiksubraveti,

.tfvars files are only for root module variables. The arguments inside the module block are the only way to set variables for child modules.

One way to think about it is that the .tfvars files together serve as a sort of virtual module block for the root module, because the root module is being “called” directly by you at the command line, rather than from within the configuration.

To set that child module variable from a root module variable will require declaring it also as a root module variable and then passing it along inside the module block, like this:

variable "orc8r_domain_name" {
  type = string

module "orc8r-app" {
  source = "./modules/orc8r-app"

  orc8r_domain_name = var.orc8r_domain_name
  # ...

I’ve shown the variable block and the module block together here for the ease of sharing the example snippet, but as @stuart-c noted it’s conventional to put variable blocks in a file called and module calls in other files, so if you honor that convention then these two blocks would actually be in two separate files in your root module directory.

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Got it. Thanks @apparentlymart for helping me understand this better. I will structure my files this way.