Depends_on for explicit dependencies in Terraform - Mini Project: Build & Apply

Depends_on for explicit dependencies

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

🎯 Goal: Build a Terraform configuration where the virtual machine resource explicitly depends on the virtual network resource using depends_on.

📋 What You'll Learn

Create a virtual network resource named my_vnet with address space 10.0.0.0/16.

Create a virtual machine resource named my_vm.

Use depends_on in the virtual machine resource to explicitly depend on the virtual network resource.

💡 Why This Matters

🌍 Real World

In real cloud projects, some resources must be created only after others are ready. Using depends_on ensures Terraform respects these dependencies.

💼 Career

Cloud engineers and DevOps professionals use depends_on to control resource creation order and avoid deployment errors.

1

Create the virtual network resource

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

Terraform

# Your code here to create azurerm_virtual_network.my_vnet

Need a hint?

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

2

Create the virtual machine resource

Add a Terraform resource block named azurerm_virtual_machine.my_vm with a placeholder configuration (name, location, resource group). Do not add depends_on yet.

Terraform

resource "azurerm_virtual_network" "my_vnet" {
  name                = "myVnet"
  address_space       = ["10.0.0.0/16"]
  location            = "East US"
  resource_group_name = "myResourceGroup"
}

# Your code here to create azurerm_virtual_machine.my_vm without depends_on

Need a hint?

Create resource "azurerm_virtual_machine" "my_vm" { ... } with basic properties like name, location, and resource_group_name.

3

Add depends_on to the virtual machine

Inside the azurerm_virtual_machine.my_vm resource block, add depends_on = [azurerm_virtual_network.my_vnet] to explicitly depend on the virtual network.

Terraform

resource "azurerm_virtual_network" "my_vnet" {
  name                = "myVnet"
  address_space       = ["10.0.0.0/16"]
  location            = "East US"
  resource_group_name = "myResourceGroup"
}

resource "azurerm_virtual_machine" "my_vm" {
  name                  = "myVM"
  location              = "East US"
  resource_group_name   = "myResourceGroup"
  network_interface_ids = []
  vm_size               = "Standard_DS1_v2"
  # Other required VM settings omitted for brevity
  # Add depends_on here
}

Need a hint?

Add depends_on = [azurerm_virtual_network.my_vnet] inside the my_vm resource block.

4

Complete the Terraform configuration

Add the required provider block for AzureRM with version constraint "~> 3.0" and a resource group resource named myResourceGroup with location East US.

Terraform

resource "azurerm_virtual_network" "my_vnet" {
  name                = "myVnet"
  address_space       = ["10.0.0.0/16"]
  location            = "East US"
  resource_group_name = "myResourceGroup"
}

resource "azurerm_virtual_machine" "my_vm" {
  name                  = "myVM"
  location              = "East US"
  resource_group_name   = "myResourceGroup"
  network_interface_ids = []
  vm_size               = "Standard_DS1_v2"
  depends_on            = [azurerm_virtual_network.my_vnet]
  # Other required VM settings omitted for brevity
}

# Add provider and resource group below

Need a hint?

Add provider "azurerm" { version = "~> 3.0" } and a resource group resource named myResourceGroup with location East US.