Create an Azure virtual machine scale set using Terraform

Terraform enables the definition, preview, and deployment of cloud infrastructure. Using Terraform, you create configuration files using HCL syntax. The HCL syntax allows you to specify the cloud provider - such as Azure - and the elements that make up your cloud infrastructure. After you create your configuration files, you create an execution plan that allows you to preview your infrastructure changes before they're deployed. Once you verify the changes, you apply the execution plan to deploy the infrastructure.

Azure virtual machine scale sets allow you to configure identical VMs. The number of VM instances can adjust based on demand or a schedule. For more information, see Automatically scale a virtual machine scale set in the Azure portal.

In this article, you learn how to:

  • Set up a Terraform deployment
  • Use variables and outputs for Terraform deployment
  • Create and deploy network infrastructure
  • Create and deploy a virtual machine scale set and attach it to the network
  • Create and deploy a jumpbox to connect to the VMs via SSH

1. Configure your environment

  • Azure subscription: If you don't have an Azure subscription, create a free account before you begin.

2. Implement the Terraform code

  1. Create a directory in which to test the sample Terraform code and make it the current directory.

  2. Create a file named main.tf and insert the following code:

    terraform {
      required_version = ">=0.12"
      
      required_providers {
        azurerm = {
          source = "hashicorp/azurerm"
          version = "~>2.0"
        }
      }
    }
    
    provider "azurerm" {
      features {}
    }
    
    resource "azurerm_resource_group" "vmss" {
     name     = var.resource_group_name
     location = var.location
     tags     = var.tags
    }
    
    resource "random_string" "fqdn" {
     length  = 6
     special = false
     upper   = false
     number  = false
    }
    
    resource "azurerm_virtual_network" "vmss" {
     name                = "vmss-vnet"
     address_space       = ["10.0.0.0/16"]
     location            = var.location
     resource_group_name = azurerm_resource_group.vmss.name
     tags                = var.tags
    }
    
    resource "azurerm_subnet" "vmss" {
     name                 = "vmss-subnet"
     resource_group_name  = azurerm_resource_group.vmss.name
     virtual_network_name = azurerm_virtual_network.vmss.name
     address_prefixes       = ["10.0.2.0/24"]
    }
    
    resource "azurerm_public_ip" "vmss" {
     name                         = "vmss-public-ip"
     location                     = var.location
     resource_group_name          = azurerm_resource_group.vmss.name
     allocation_method            = "Static"
     domain_name_label            = random_string.fqdn.result
     tags                         = var.tags
    }
    
    resource "azurerm_lb" "vmss" {
     name                = "vmss-lb"
     location            = var.location
     resource_group_name = azurerm_resource_group.vmss.name
    
     frontend_ip_configuration {
       name                 = "PublicIPAddress"
       public_ip_address_id = azurerm_public_ip.vmss.id
     }
    
     tags = var.tags
    }
    
    resource "azurerm_lb_backend_address_pool" "bpepool" {
     loadbalancer_id     = azurerm_lb.vmss.id
     name                = "BackEndAddressPool"
    }
    
    resource "azurerm_lb_probe" "vmss" {
     resource_group_name = azurerm_resource_group.vmss.name
     loadbalancer_id     = azurerm_lb.vmss.id
     name                = "ssh-running-probe"
     port                = var.application_port
    }
    
    resource "azurerm_lb_rule" "lbnatrule" {
       resource_group_name            = azurerm_resource_group.vmss.name
       loadbalancer_id                = azurerm_lb.vmss.id
       name                           = "http"
       protocol                       = "Tcp"
       frontend_port                  = var.application_port
       backend_port                   = var.application_port
       backend_address_pool_id        = azurerm_lb_backend_address_pool.bpepool.id
       frontend_ip_configuration_name = "PublicIPAddress"
       probe_id                       = azurerm_lb_probe.vmss.id
    }
    
    resource "azurerm_virtual_machine_scale_set" "vmss" {
     name                = "vmscaleset"
     location            = var.location
     resource_group_name = azurerm_resource_group.vmss.name
     upgrade_policy_mode = "Manual"
    
     sku {
       name     = "Standard_DS1_v2"
       tier     = "Standard"
       capacity = 2
     }
    
     storage_profile_image_reference {
       publisher = "Canonical"
       offer     = "UbuntuServer"
       sku       = "16.04-LTS"
       version   = "latest"
     }
    
     storage_profile_os_disk {
       name              = ""
       caching           = "ReadWrite"
       create_option     = "FromImage"
       managed_disk_type = "Standard_LRS"
     }
    
     storage_profile_data_disk {
       lun          = 0
       caching        = "ReadWrite"
       create_option  = "Empty"
       disk_size_gb   = 10
     }
    
     os_profile {
       computer_name_prefix = "vmlab"
       admin_username       = var.admin_user
       admin_password       = var.admin_password
       custom_data          = file("web.conf")
     }
    
     os_profile_linux_config {
       disable_password_authentication = false
     }
    
     network_profile {
       name    = "terraformnetworkprofile"
       primary = true
    
       ip_configuration {
         name                                   = "IPConfiguration"
         subnet_id                              = azurerm_subnet.vmss.id
         load_balancer_backend_address_pool_ids = [azurerm_lb_backend_address_pool.bpepool.id]
         primary = true
       }
     }
    
     tags = var.tags
    }
    
    resource "azurerm_public_ip" "jumpbox" {
     name                         = "jumpbox-public-ip"
     location                     = var.location
     resource_group_name          = azurerm_resource_group.vmss.name
     allocation_method            = "Static"
     domain_name_label            = "${random_string.fqdn.result}-ssh"
     tags                         = var.tags
    }
    
    resource "azurerm_network_interface" "jumpbox" {
     name                = "jumpbox-nic"
     location            = var.location
     resource_group_name = azurerm_resource_group.vmss.name
    
     ip_configuration {
       name                          = "IPConfiguration"
       subnet_id                     = azurerm_subnet.vmss.id
       private_ip_address_allocation = "dynamic"
       public_ip_address_id          = azurerm_public_ip.jumpbox.id
     }
    
     tags = var.tags
    }
    
    resource "azurerm_virtual_machine" "jumpbox" {
     name                  = "jumpbox"
     location              = var.location
     resource_group_name   = azurerm_resource_group.vmss.name
     network_interface_ids = [azurerm_network_interface.jumpbox.id]
     vm_size               = "Standard_DS1_v2"
    
     storage_image_reference {
       publisher = "Canonical"
       offer     = "UbuntuServer"
       sku       = "16.04-LTS"
       version   = "latest"
     }
    
     storage_os_disk {
       name              = "jumpbox-osdisk"
       caching           = "ReadWrite"
       create_option     = "FromImage"
       managed_disk_type = "Standard_LRS"
     }
    
     os_profile {
       computer_name  = "jumpbox"
       admin_username = var.admin_user
       admin_password = var.admin_password
     }
    
     os_profile_linux_config {
       disable_password_authentication = false
     }
    
     tags = var.tags
    }
    
  3. Create a file named variables.tf to contain the project variables and insert the following code:

    variable "resource_group_name" {
       description = "Name of the resource group in which the resources will be created"
       default     = "myResourceGroup"
    }
    
    variable "location" {
       default = "eastus"
       description = "Location where resources will be created"
    }
    
    variable "tags" {
       description = "Map of the tags to use for the resources that are deployed"
       type        = map(string)
       default = {
          environment = "codelab"
       }
    }
    
    variable "application_port" {
       description = "Port that you want to expose to the external load balancer"
       default     = 80
    }
    
    variable "admin_user" {
       description = "User name to use as the admin account on the VMs that will be part of the VM scale set"
       default     = "azureuser"
    }
    
    variable "admin_password" {
       description = "Default password for admin account"
    }
    
  4. Create a file named output.tf to specify what values Terraform displays and insert the following code:

    output "vmss_public_ip_fqdn" {
       value = azurerm_public_ip.vmss.fqdn
    }
    
    output "jumpbox_public_ip_fqdn" {
       value = azurerm_public_ip.jumpbox.fqdn
    }
    
    output "jumpbox_public_ip" {
       value = azurerm_public_ip.jumpbox.ip_address
    }
    
  5. Create a file named web.conf and insert the following code:

    #cloud-config
    packages:
     - nginx
    

3. Initialize Terraform

Run terraform init to initialize the Terraform deployment. This command downloads the Azure modules required to manage your Azure resources.

terraform init

4. Create a Terraform execution plan

Run terraform plan to create an execution plan.

terraform plan -out main.tfplan

Key points:

  • The terraform plan command creates an execution plan, but doesn't execute it. Instead, it determines what actions are necessary to create the configuration specified in your configuration files. This pattern allows you to verify whether the execution plan matches your expectations before making any changes to actual resources.
  • The optional -out parameter allows you to specify an output file for the plan. Using the -out parameter ensures that the plan you reviewed is exactly what is applied.
  • To read more about persisting execution plans and security, see the security warning section.

5. Apply a Terraform execution plan

Run terraform apply to apply the execution plan to your cloud infrastructure.

terraform apply main.tfplan

Key points:

  • The terraform apply command above assumes you previously ran terraform plan -out main.tfplan.
  • If you specified a different filename for the -out parameter, use that same filename in the call to terraform apply.
  • If you didn't use the -out parameter, call terraform apply without any parameters.

6. Verify the results

  1. From the output of the terraform apply command, you see values for the following:

    • Virtual machine FQDN
    • Jumpbox FQDN
    • Jumpbox IP address
  2. Browse to the virtual machine URL to confirm a default page with the text Welcome to nginx!.

  3. Use SSH to connect to the jumpbox VM using the user name defined in the variables file and the password you specified when you ran terraform apply. For example: ssh azureuser@<ip_address>.

7. Clean up resources

When you no longer need the resources created via Terraform, do the following steps:

  1. Run terraform plan and specify the destroy flag.

    terraform plan -destroy -out main.destroy.tfplan
    

    Key points:

    • The terraform plan command creates an execution plan, but doesn't execute it. Instead, it determines what actions are necessary to create the configuration specified in your configuration files. This pattern allows you to verify whether the execution plan matches your expectations before making any changes to actual resources.
    • The optional -out parameter allows you to specify an output file for the plan. Using the -out parameter ensures that the plan you reviewed is exactly what is applied.
    • To read more about persisting execution plans and security, see the security warning section.
  2. Run terraform apply to apply the execution plan.

    terraform apply main.destroy.tfplan
    

Troubleshoot Terraform on Azure

Troubleshoot common problems when using Terraform on Azure

Next steps