Terraform keywords

What******data******** means in Terraform:**

data is one of Terraform's core keywords (called a "block type"). It tells Terraform:

"I want tolook up** existing information, not create anything new"

The main Terraform keywords are:

Examples to show the difference:

data******** = Looking up existing stuff:

data "oci_core_images" "existing_image" {
  # Find an image that already exists
}

resource******** = Creating new stuff:

resource "oci_core_instance" "my_new_server" {
  # Create a brand new virtual machine
}

Think of it like:

• data = "Show me what's already there" 🔍

• resource = "Build me something new" 🔨

So yes, data is a special Terraform word that you must use exactly as written! 👍

variable** - Define Input Values**

What it does:

variable lets you pass values INTO your Terraform configuration (like function parameters)

Think of it like:

A form field that someone fills out before running Terraform 📝

Example:

variable "server_name" {
  description = "What should we call the server?"
  type        = string
  default     = "my-server"
}

How it works:

• Someone runs: terraform apply -var="server_name=web-server"

• Or you put it in a .tfvars file

• Use it later: name = var.server_name

output** - Export Values**

What it does:

output shows important information AFTER Terraform creates things

Think of it like:

A receipt that shows you important details after shopping 🧾

Example:

output "server_ip_address" {
  description = "The public IP of our new server"
  value       = oci_core_instance.my_server.public_ip
}

How it works:

• After terraform apply, you'll see: server_ip_address = "123.456.789.0"

• Other Terraform configs can use this value

• Useful for showing connection info, URLs, etc.

locals** - Calculate Values**

What it does:

locals creates calculated values that you use multiple times in the same configuration

Think of it like:

A calculator or notepad for doing math once and reusing the answer 🧮

Example:

locals {
  common_tags = {
    Environment = "production"
    Team        = "web-team"
    CreatedBy   = "terraform"
  }
  
  server_count = var.users_count * 2
}

How it works:

• Calculate once: local.server_count

• Use everywhere: count = local.server_count

• Keeps your config DRY (Don't Repeat Yourself)

module** - Use Reusable Code**

What it does:

module imports pre-written Terraform code (like using a template or recipe)

Think of it like:

Using a cake mix instead of measuring flour, sugar, etc. from scratch 🍰

Example:

module "web_server" {
  source = "./modules/web-server"
  
  server_name = "my-website"
  server_size = "small"
}

How it works:

• Points to a folder with Terraform code (./modules/web-server)

• Or downloads from Terraform Registry, GitHub, etc.

• Passes variables to the module

• The module creates multiple resources for you

• Like calling a function that does lots of work!

Quick Summary:

• variable = "Tell me what you want" ⬅️

• output = "Here's what I made" ➡️

• locals = "Let me calculate this once" 🧮

• module = "Use this pre-made template" 📦