How to give a .tf file as input in Terraform Apply command?

Question

I'm a beginner in Terraform.

I have a directory which contains 2 .tf files.

Now I want to run Terraform Apply on a selected .tf file & neglect the other one.

Can I do that? If yes, how? If no, why & what is the best practice?

Answer 1

You can't selectively apply one file and then the other. Two ways of (maybe) achieving what you're going for:

• Use the -target flag to target resource(s) in one file and then the other.
• Put each file (or more broadly, group of resources, which might be multiple files) in separate "modules" (folders). You can then apply them separately.

Answer 2

You can use the terraform -target flag. Or You can have multiple terraform modules in a separate directory. And then you can terraform apply there. As an example, assume you have 3 .tf files separately. But you need to run more than just one of them at the same time. If you also, need to run them more often it's better to have a terraform module.

terraform
    |--frontend
    |  └──main.tf
    |--backend-1
    |  └──main.tf
    |--backend-2
    |  └──main.tf
    |--modules-1
    |  └──module.tf

Inside the module.tf you can define which files you need to apply.

module "frontend" {
  source = "terraform/frontend"
}

module "backend-1" {
  source = "terraform/backend-1"
} 

Then issue terraform apply staying at the module directory. And it will automatically import instances inside those paths and apply it.