Create an Azure virtual machine scale set from a Packer custom image by using Terraform

Artikkel
03/15/2024

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 your Terraform deployment
Use variables and outputs for Terraform deployment
Create and deploy a network infrastructure
Create a custom virtual machine image by using Packer
Create and deploy a virtual machine scale set by using the custom image
Create and deploy a jumpbox

1. Configure your environment

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

Configure Terraform: If you haven't already done so, configure Terraform using one of the following options:

2. Create a Packer image

Install Packer.

Key points:
- To confirm that you have access to the Packer executable, run the following command: packer -v.
- Depending on your environment, you might need to set your path and reopen the command-line.
Run az group create to create a resource group to hold the Packer image.
```
az group create -n myPackerImages -l eastus
```
Run az ad sp create-for-rbac to enable Packer to authenticate to Azure using a service principal.
```
az ad sp create-for-rbac --role Contributor --scopes /subscriptions/<subscription_id> --query "{ client_id: appId, client_secret: password, tenant_id: tenant }"
```
Key points:
- Make note of the output values (appId, client_secret, tenant_id).
Run az account show to display the current Azure subscription.
```
az account show --query "{ subscription_id: id }"
```

Create a Packer template variables file named ubuntu.pkr.hcl and insert the following code. Update the highlighted lines with your service principal and Azure subscription information.

packer {
  required_plugins {
    azure = {
      source  = "github.com/hashicorp/azure"
      version = "~> 2"
    }
  }
}

variable client_id {
  type    = string
  default = null
}
variable client_secret {
  type    = string
  default = null
}

variable subscription_id {
  type    = string
  default = null
}

variable tenant_id {
  type    = string
  default = null
}

variable location {
  default = "eastus"
}

variable "image_resource_group_name" {
  description = "Name of the resource group in which the Packer image will be created"
  default     = "myPackerImages"
}

variable "oidc_request_url" {
  default = null
}

variable "oidc_request_token" {
  default = null
}

# arm builder
source "azure-arm" "builder" {
  client_id                         = var.client_id
  client_secret                     = var.client_secret
  image_offer                       = "UbuntuServer"
  image_publisher                   = "canonical"
  image_sku                         = "16.04-LTS"
  location                          = var.location
  managed_image_name                = "myPackerImage"
  managed_image_resource_group_name = var.image_resource_group_name
  os_type                           = "Linux"
  subscription_id                   = var.subscription_id
  tenant_id                         = var.tenant_id
  oidc_request_url                  = var.oidc_request_url
  oidc_request_token                = var.oidc_request_token
  vm_size                           = "Standard_DS2_v2"
  azure_tags = {
    "dept" : "Engineering",
    "task" : "Image deployment",
  }
}

build {
  sources = ["source.azure-arm.builder"]
  provisioner "shell" {
    execute_command = "chmod +x {{ .Path }}; {{ .Vars }} sudo -E sh '{{ .Path }}'"
    inline = [
      "apt-get update",
      "apt-get upgrade -y",
      "apt-get -y install nginx",
      "/usr/sbin/waagent -force -deprovision+user && export HISTSIZE=0 && sync",
    ]
  }
}

Key points:

Set the client_id, client_secret, and tenant_id fields to the respective values from your service principal.
Set the subscription_id field to your Azure subscription ID.

Build the Packer image.
```
packer build ubuntu.json
```

3. Implement the Terraform code

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

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

terraform {

  required_version = ">=0.12"

  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~>3.0"
    }
    azapi = {
      source  = "Azure/azapi"
      version = "~> 1.0"
    }
    local = {
      source  = "hashicorp/local"
      version = "2.4.0"
    }
    random = {
      source  = "hashicorp/random"
      version = "3.5.1"
    }
    tls = {
      source  = "hashicorp/tls"
      version = "4.0.4"
    }
  }
}

provider "azurerm" {
  features {
    resource_group {
      prevent_deletion_if_contains_resources = false
    }
  }
}

resource "random_pet" "id" {}

resource "azurerm_resource_group" "vmss" {
  name     = coalesce(var.resource_group_name, "201-vmss-packer-jumpbox-${random_pet.id.id}")
  location = var.location
  tags     = var.tags
}

resource "random_string" "fqdn" {
  length  = 6
  special = false
  upper   = false
  numeric = 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" {
  loadbalancer_id = azurerm_lb.vmss.id
  name            = "ssh-running-probe"
  port            = var.application_port
}

resource "azurerm_lb_rule" "lbnatrule" {
  loadbalancer_id                = azurerm_lb.vmss.id
  name                           = "http"
  protocol                       = "Tcp"
  frontend_port                  = var.application_port
  backend_port                   = var.application_port
  backend_address_pool_ids       = [azurerm_lb_backend_address_pool.bpepool.id]
  frontend_ip_configuration_name = "PublicIPAddress"
  probe_id                       = azurerm_lb_probe.vmss.id
}

data "azurerm_resource_group" "image" {
  name = var.packer_resource_group_name
}

data "azurerm_image" "image" {
  name                = var.packer_image_name
  resource_group_name = data.azurerm_resource_group.image.name
}

resource "azapi_resource" "ssh_public_key" {
  type      = "Microsoft.Compute/sshPublicKeys@2022-11-01"
  name      = random_pet.id.id
  location  = azurerm_resource_group.vmss.location
  parent_id = azurerm_resource_group.vmss.id
}

resource "azapi_resource_action" "ssh_public_key_gen" {
  type        = "Microsoft.Compute/sshPublicKeys@2022-11-01"
  resource_id = azapi_resource.ssh_public_key.id
  action      = "generateKeyPair"
  method      = "POST"

  response_export_values = ["publicKey", "privateKey"]
}

resource "random_password" "password" {
  count  = var.admin_password == null ? 1 : 0
  length = 20
}

locals {
  admin_password = try(random_password.password[0].result, var.admin_password)
}

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 {
    id = data.azurerm_image.image.id
  }

  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       = local.admin_password
  }

  os_profile_linux_config {
    disable_password_authentication = true

    ssh_keys {
      path     = "/home/azureuser/.ssh/authorized_keys"
      key_data = azapi_resource_action.ssh_public_key_gen.output.publicKey
    }
  }

  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 = local.admin_password
  }

  os_profile_linux_config {
    disable_password_authentication = true

    ssh_keys {
      path     = "/home/azureuser/.ssh/authorized_keys"
      key_data = azapi_resource_action.ssh_public_key_gen.output.publicKey
    }
  }

  tags = var.tags
}

Create a file named variables.tf to contain the project variables and insert the following code:

variable "packer_resource_group_name" {
  description = "Name of the resource group in which the Packer image will be created"
  default     = "myPackerImages"
}

variable "packer_image_name" {
  description = "Name of the Packer image"
  default     = "myPackerImage"
}

variable "resource_group_name" {
  description = "Name of the resource group in which the Packer image  will be created"
  default     = null
}

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"
  default     = null
}

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
}

4. Initialize Terraform

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

terraform init -upgrade

Key points:

The -upgrade parameter upgrades the necessary provider plugins to the newest version that complies with the configuration's version constraints.

5. 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.

6. Apply a Terraform execution plan

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

terraform apply main.tfplan

Key points:

The example terraform apply command 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.

7. Verify the results

From the output of the terraform apply command, you see values for the following:
- Virtual machine FQDN
- Jumpbox FQDN
- Jumpbox IP address
Browse to the virtual machine URL to confirm a default page with the text Welcome to nginx!.
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>.

8. Clean up resources

Delete virtual machine scale set

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

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.
Run terraform apply to apply the execution plan.
```
terraform apply main.destroy.tfplan
```

Delete Packer image and resource group

Run az group delete to delete the resource group used to contain the Packer image. The Packer image is also deleted.

az group delete --name myPackerImages --yes

Troubleshoot Terraform on Azure

Troubleshoot common problems when using Terraform on Azure

Next steps

Learn more about using Terraform in Azure

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Create an Azure virtual machine scale set from a Packer custom image by using Terraform

1. Configure your environment

2. Create a Packer image

3. Implement the Terraform code

4. Initialize Terraform

5. Create a Terraform execution plan

6. Apply a Terraform execution plan

7. Verify the results

8. Clean up resources

Delete virtual machine scale set

Delete Packer image and resource group

Troubleshoot Terraform on Azure

Next steps

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