Resource dependencies (implicit) in Terraform - Mini Project: Build & Apply

Terraform Resource Dependencies (Implicit)

📖 Scenario: You are setting up a simple cloud infrastructure using Terraform. You want to create a virtual network and then create a virtual machine inside that network. The virtual machine must be created only after the network is ready.

🎯 Goal: Build a Terraform configuration that creates a virtual network and a virtual machine. Use implicit resource dependencies so Terraform knows to create the network before the virtual machine.

📋 What You'll Learn

Create a resource called azurerm_virtual_network named main_network with address space 10.0.0.0/16.

Create a resource called azurerm_subnet named main_subnet inside main_network with address prefix 10.0.1.0/24.

Create a resource called azurerm_network_interface named main_nic attached to main_subnet.

Create a resource called azurerm_linux_virtual_machine named main_vm that uses main_nic.

Use implicit dependencies by referencing resource attributes to ensure correct creation order.

💡 Why This Matters

🌍 Real World

Cloud engineers often create networks and virtual machines that depend on each other. Using implicit dependencies in Terraform helps automate the correct creation order without extra configuration.

💼 Career

Understanding resource dependencies is essential for infrastructure as code roles, ensuring reliable and maintainable cloud deployments.

1

Create the virtual network resource

Create a resource block for azurerm_virtual_network named main_network with the address space set to ["10.0.0.0/16"].

Terraform

# Your code here

Need a hint?

Use resource "azurerm_virtual_network" "main_network" { ... } and set address_space to ["10.0.0.0/16"].

2

Add a subnet resource inside the virtual network

Create a resource block for azurerm_subnet named main_subnet with the address prefix "10.0.1.0/24". Reference the virtual network ID from azurerm_virtual_network.main_network.id to attach the subnet to the network.

Terraform

resource "azurerm_virtual_network" "main_network" {
  name                = "main-network"
  address_space       = ["10.0.0.0/16"]
  location            = "eastus"
  resource_group_name = "myResourceGroup"
}

# Your code here

Need a hint?

Reference the virtual network name using azurerm_virtual_network.main_network.name inside the subnet resource.

3

Create a network interface attached to the subnet

Create a resource block for azurerm_network_interface named main_nic. Set the subnet_id to azurerm_subnet.main_subnet.id to attach it to the subnet.

Terraform

resource "azurerm_virtual_network" "main_network" {
  name                = "main-network"
  address_space       = ["10.0.0.0/16"]
  location            = "eastus"
  resource_group_name = "myResourceGroup"
}

resource "azurerm_subnet" "main_subnet" {
  name                 = "main-subnet"
  resource_group_name  = "myResourceGroup"
  virtual_network_name = azurerm_virtual_network.main_network.name
  address_prefixes     = ["10.0.1.0/24"]
}

# Your code here

Need a hint?

Inside ip_configuration, set subnet_id to azurerm_subnet.main_subnet.id.

4

Create a Linux virtual machine using the network interface

Create a resource block for azurerm_linux_virtual_machine named main_vm. Set the network_interface_ids to a list containing azurerm_network_interface.main_nic.id. Use name as "main-vm", resource_group_name as "myResourceGroup", and location as "eastus". Set size to "Standard_DS1_v2". Use admin_username as "adminuser" and admin_password as "Password1234!". Set os_disk with caching as "ReadWrite" and storage_account_type as "Standard_LRS". Use source_image_reference for Ubuntu 20.04 LTS with publisher "Canonical", offer "UbuntuServer", sku "20_04-lts", and version "latest". This will implicitly depend on the network interface.

Terraform

resource "azurerm_virtual_network" "main_network" {
  name                = "main-network"
  address_space       = ["10.0.0.0/16"]
  location            = "eastus"
  resource_group_name = "myResourceGroup"
}

resource "azurerm_subnet" "main_subnet" {
  name                 = "main-subnet"
  resource_group_name  = "myResourceGroup"
  virtual_network_name = azurerm_virtual_network.main_network.name
  address_prefixes     = ["10.0.1.0/24"]
}

resource "azurerm_network_interface" "main_nic" {
  name                = "main-nic"
  location            = "eastus"
  resource_group_name = "myResourceGroup"

  ip_configuration {
    name                          = "internal"
    subnet_id                     = azurerm_subnet.main_subnet.id
    private_ip_address_allocation = "Dynamic"
  }
}

# Your code here

Need a hint?

Reference the network interface ID in network_interface_ids to create an implicit dependency.