Key Terraform Rule in Execution, files, folders and directories

 

 Key Terraform Rule

Terraform loads and merges ALL .tf files in a directory automatically.

There is:

• ❌ no “main file”

• ❌ no execution order by filename

• ✅ one configuration per directory

So:

terraform apply

applies everything in that folder.

---

✅ How You SHOULD structure your files

📁 Recommended folder structure

terraform-lab/
├── provider.tf
├── data.tf
├── instance.tf
├── outputs.tf
├── variables.tf

Terraform reads them all together.

LAB- BREAK YOUR MAIN.TF INTO DIFFERENT COMPONENTS

provider.tf

provider "aws" {
  region = "us-east-1"
}

---

data.tf

data "aws_vpc" "default" {
  default = true
}

data "aws_subnets" "default" {
  filter {
    name   = "vpc-id"
    values = [data.aws_vpc.default.id]
  }
}

---

instance.tf

resource "aws_instance" "web" {
  ami           = "ami-0c02fb55956c7d316"
  instance_type = "t3.micro"
  subnet_id     = data.aws_subnets.default.ids[0]

  tags = {
    Name = "terraform-lab"
  }
}

---

outputs.tf

output "instance_id" {
  value = aws_instance.web.id
}

---

▶️ Running Terraform

From the directory:

terraform init
terraform plan
terraform apply

Terraform automatically:

• loads all .tf files

• builds the dependency graph

• applies in the correct order

---

❌ Common misconception

“Terraform executes files top to bottom”

Wrong.

Terraform:

• builds a dependency graph

• executes based on references

• ignores file order and filenames

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🧠 KEY TAKEAWYS

Terraform directory = one application
.tf files = chapters in the same book

You don’t run chapters — you run the book.

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🧪 Advanced (Optional): Lab separation strategies

Option A — New folder per lab (recommended for beginners)

labs/
├── lab1-default-vpc/
├── lab2-alb/
├── lab3-asg/

Option B — Same folder, comment/uncomment (not ideal)

Option C — Use variables / count (advanced)

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⚠️ One important rule

Terraform only reads files in the current directory.

Subfolders are ignored unless you use modules (advanced topic).

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✅ 

• You don’t “apply a file”

• You apply a directory

• Terraform merges all .tf files automatically

• File naming is for human readability only

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🧠 One-sentence takeaway for students

Terraform applies directories, not files.