Cloud-Init With Terraform • Jamie Phillips

Did you know that you could use cloud-init with Terraform? I didn’t realize until recently. No, I am not talking about a template and passing it via user data, but defining a cloud-init template in Terraform. Let’s get into it.

The Plan

Pick your favorite cloud provider to try this, as all you need is a Linux VM. I will be using Azure to spin up an Ubuntu server and apply a cloud-init template. I will have cloud-init install the tool HTTPie.

Initial Terraform

We are going to get started like we always do by defining a Terraform block and our provider.

terraform {
  required_version = ">= 0.14.3"
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "2.44.0"
    }
  }
}

provider "azurerm" {
  features {}
}

I am using the Azure CLI to login and set my subscription.

Define our VM

Let’s now create our VM.

resource "azurerm_resource_group" "cloudinit" {
  name     = "cloudinit-resources"
  location = "East US"
}

resource "azurerm_virtual_network" "cloudinit" {
  name                = "cloudinit-network"
  address_space       = ["10.0.0.0/16"]
  location            = azurerm_resource_group.cloudinit.location
  resource_group_name = azurerm_resource_group.cloudinit.name
}

resource "azurerm_subnet" "cloudinit" {
  name                 = "internal"
  resource_group_name  = azurerm_resource_group.cloudinit.name
  virtual_network_name = azurerm_virtual_network.cloudinit.name
  address_prefixes     = ["10.0.2.0/24"]
}

resource "azurerm_public_ip" "cloudinit" {
  name                = "cloudinit-pip"
  location            = azurerm_resource_group.cloudinit.location
  resource_group_name = azurerm_resource_group.cloudinit.name
  allocation_method   = "Dynamic"
}

resource "azurerm_network_security_group" "cloudinit" {
  name                = "cloudinit-sg"
  location            = azurerm_resource_group.cloudinit.location
  resource_group_name = azurerm_resource_group.cloudinit.name

  security_rule {
    name                       = "SSH"
    priority                   = 1001
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "*"
    destination_port_range     = "22"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  }
}

resource "azurerm_network_interface" "cloudinit" {
  name                = "cloudinit-nic"
  location            = azurerm_resource_group.cloudinit.location
  resource_group_name = azurerm_resource_group.cloudinit.name

  ip_configuration {
    name                          = "cloudinit-nic-config"
    subnet_id                     = azurerm_subnet.cloudinit.id
    private_ip_address_allocation = "Dynamic"
    public_ip_address_id          = azurerm_public_ip.cloudinit.id
  }
}

resource "azurerm_network_interface_security_group_association" "cloudinit" {
  network_interface_id      = azurerm_network_interface.cloudinit.id
  network_security_group_id = azurerm_network_security_group.cloudinit.id
}

resource "azurerm_linux_virtual_machine" "cloudinit" {
  name                = "cloudinit-machine"
  resource_group_name = azurerm_resource_group.cloudinit.name
  location            = azurerm_resource_group.cloudinit.location
  size                = "Standard_B1s"
  admin_username      = "cloudinit"
  admin_password      = "HKKRoD24XLBzxdD"


  # This is where we pass our cloud-init.
  custom_data = ""

  disable_password_authentication = false

  network_interface_ids = [
    azurerm_network_interface.cloudinit.id,
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }

  source_image_reference {
    publisher = "Canonical"
    offer     = "UbuntuServer"
    sku       = "18.04-LTS"
    version   = "latest"
  }
}

output "public_ip" {
  value = azurerm_linux_virtual_machine.cloudinit.public_ip_address
}

Creating our cloud-init

The resource documentation can be found here. We are going to create this in our Terraform after the provider since it is a data block, and that is the convention that I use.

data "template_cloudinit_config" "config" {
  gzip          = true
  base64_encode = true

  # Main cloud-config configuration file.
  part {
    content_type = "text/cloud-config"
    content      = "packages: ['httpie']"
  }
}

Now we can go back to our VM resource and pass that to the custom_data property.

resource "azurerm_linux_virtual_machine" "cloudinit" {
  name                = "cloudinit-machine"
  resource_group_name = azurerm_resource_group.cloudinit.name
  location            = azurerm_resource_group.cloudinit.location
  size                = "Standard_B1s"
  admin_username      = "cloudinit"
  admin_password      = "HKKRoD24XLBzxdD"


  # This is where we pass our cloud-init.
  custom_data = data.template_cloudinit_config.config.rendered

  disable_password_authentication = false
  
  # Abbreviated
}

That’s it, and we can now execute it.

Creating and validating the VM

Time to initialize our Terraform and apply.

$ terraform init
Terraform has been successfully initialized!

$ terraform apply -auto-approve
Apply complete! Resources: 8 added, 0 changed, 0 destroyed.

With our VM created successfully, we can use the Azure CLI to check to see if it has a status of running.

$ az vm get-instance-view /
   -n cloudinit-machine /
   -g cloudinit-resources /
   --query instanceView.statuses[1] /
   -o table
   
Code                Level    DisplayStatus
------------------  -------  ---------------
PowerState/running  Info     VM running

Once the status reports that it’s running, we need to ssh into the server and verify the HTTPie installation. We will need the public ip of the instance, which we can get from Terraform.

$ terraform output publc_ip
"XX.XX.XXX.XXX"

Now we can SSH in and check HTTPie.

$ ssh cloudinit@XX.XX.XXX.XXX

$ cloudinit@cloudinit-machine:~$ http --version
0.9.8

$ cloudinit@cloudinit-machine:~$ exit
logout
Connection to XX.XX.XXX.XXX closed.

Conclusion

That’s it; that is how you use cloud-init to configure your VM upon creation. Don’t forget to clean up your resources.

Thanks for reading,

Jamie

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