A managed resource "azurerm_network_interface" has not been declared in module

I’m running a "terraform plan" against my Linux VM and I’m receiving the following error:

│ Error: Reference to undeclared resource
│ 
│   on .terraform/modules/vm-ansiblecontroller/virtual-machine/linux/outputs.tf line 13, in output "nic_id":
│   13:   value = azurerm_network_interface.nic-linux.id
│ 
│ A managed resource "azurerm_network_interface" "nic-linux" has not been declared in module.vm-ansiblecontroller.

I haven’t included any code from my RGs & vNets, as I’m hoping what I have included is enough to solve this.

Any assistance would be appreciated, I just can’t figure it out

module "vm-ansiblecontroller" {
  resource_group_name = module.rg-ansiblecontroller.resource_group_name
  location            = local.location
  linux_machine_name  = "linux-test1"
  tags                = var.tags

  nic_id = module.vm-ansiblecontroller.nic_id
  subnet_id = module.subnet-networkcore.subnet_id

  virtual_machine_size = "Standard_D2"

  admin_username       = "jpadmin"
  admin_ssh_public_key = file("~/.ssh/id_rsa.pub")

  source_image_publisher = "Canonical"
  source_image_offer     = "UbuntuServer"
  source_image_sku       = "16.04-LTS"
  source_image_version   = "latest"

  operating_system_disk_cache = "ReadWrite"
  operating_system_disk_type  = "Standard_LRS"

  ip_configuration_name         = "internal"
  private_ip_address_allocation = "Dynamic"

  public_ip_allocation_method = "Static"
  public_ip_sku               = "Standard"

}

modules/virtualmachine/main.tf

    # Linux Virtual Machine
    resource "azurerm_linux_virtual_machine" "vm-linux" {
    
      name                = var.linux_machine_name
      location            = var.location
      resource_group_name = var.resource_group_name
      tags                = var.tags
    
      size                            = var.virtual_machine_size
      admin_username                  = var.admin_username
      disable_password_authentication = true
      # network_interface_ids           = [azurerm_network_interface.nic-linux.id]
      network_interface_ids = var.nic_id
    
      admin_ssh_key {
        username   = var.admin_username
        public_key = var.admin_ssh_public_key
      }
    
      source_image_reference {
    
        publisher = var.source_image_publisher
        offer     = var.source_image_offer
        sku       = var.source_image_sku
        version   = var.source_image_version
      }
    
      os_disk {
        caching              = var.operating_system_disk_cache
        storage_account_type = var.operating_system_disk_type
      }
    }
    
    # Network Interfaces for Linux VM
    
    resource "azurerm_network_interface" "nic-linux" {
      name                = var.linux_machine_name
      location            = var.location
      resource_group_name = var.resource_group_name
      tags                = var.tags
    
      ip_configuration {
        name                          = var.ip_configuration_name
        # subnet_id                     = azurerm_subnet.subnet.id
        subnet_id                     = var.subnet_id
        private_ip_address_allocation = var.private_ip_address_allocation
        public_ip_address_id          = azurerm_public_ip.pip-linux.id
      }
    }
    resource "azurerm_public_ip" "pip-linux" {
      name                = var.linux_machine_name
      location            = var.location
      resource_group_name = var.resource_group_name
      tags                = var.tags
    
      allocation_method = var.public_ip_allocation_method
      sku               = var.public_ip_sku
    }

modules/virtualmachine/variables.tf

# VM Name
variable "linux_machine_name" {
  description = "Linux Virtual Machine Name - If left blank generated from metadata module"
  type        = string
  default     = ""
}

variable "resource_group_name" {
  description = "Resource group name"
  type        = string
}

variable "location" {
  description = "Azure region"
  type        = string
}

variable "tags" {
  description = "tags to be applied to resources"
  type        = map(string)
}

# VM Size
variable "virtual_machine_size" {
  description = "Instance size to be provisioned"
  type        = string
}

variable "admin_username" {
  description = "names to be applied to resources"
  type        = string
}

variable "admin_ssh_public_key" {
  description = "(Linux) Public SSH Key - Generated if left blank"
  type        = string
  default     = ""
  sensitive   = true
}

# Operating System
variable "source_image_publisher" {
  description = "Operating System Publisher"
  type        = string
}

variable "source_image_offer" {
  description = "Operating System Name"
  type        = string
}

variable "source_image_sku" {
  description = "Operating System SKU"
  type        = string
}

variable "source_image_version" {
  description = "Operating System Version"
  type        = string
  default     = "latest"
}

# Operating System Disk
variable "operating_system_disk_cache" {
  description = "Type of caching to use on the OS disk - Options: None, ReadOnly or ReadWrite"
  type        = string
  default     = "ReadWrite"
}

variable "operating_system_disk_type" {
  description = "Type of storage account to use with the OS disk - Options: Standard_LRS, StandardSSD_LRS or Premium_LRS"
  type        = string
  default     = "StandardSSD_LRS"
}

variable "ip_configuration_name" {
  description = "ip configuration name"
  type        = string
  default     = ""
}

# Networking
variable "nic_id" {
  type        = list(string)
  description = "ID of the nic"
}

variable "subnet_id" {
  type        = string
  description = "ID of the subnet"
}

variable "private_ip_address_allocation" {
  type        = string
  description = "Private ip allocation method"
}

variable "public_ip_allocation_method" {
  type        = string
  description = "Public ip allocation method"
}


variable "public_ip_sku" {
  description = "SKU to be used with this public IP - Basic or Standard"
  type        = string
  default     = "Standard"
}

modules/virtualmachine/outputs.tf

output "nic_id" {
  description = "ids of the vm nics provisoned."
  value = azurerm_network_interface.nic-linux.id
}

NEW ERROR:

Error: Invalid value for module argument
│
│   on compute_lin_vm.tf line 10, in module "vm-ansiblecontroller":
│   10:   nic_id = module.vm-ansiblecontroller.nic_id
│
│ The given value is not suitable for child module variable "nic_id" defined at
│ .terraform/modules/vm-ansiblecontroller/virtual-machine/linux/variables.tf:83,1-18: list of string required.

>Solution :

You placed your azurerm_network_interface inside azurerm_linux_virtual_machine. It should be:

resource "azurerm_linux_virtual_machine" "vm-linux" {

  name                = var.linux_machine_name
  location            = var.location
  resource_group_name = var.resource_group_name
  tags                = var.tags

  size                            = var.virtual_machine_size
  admin_username                  = var.admin_username
  disable_password_authentication = true
  # network_interface_ids           = [azurerm_network_interface.nic-linux.id]
  network_interface_ids           = var.nic_id

  admin_ssh_key {
    username   = var.admin_username
    public_key = var.admin_ssh_public_key
  }

  source_image_id = var.source_image_id
  custom_data     = var.custom_data

  source_image_reference {

    publisher = var.source_image_publisher
    offer     = var.source_image_offer
    sku       = var.source_image_sku
    version   = var.source_image_version
  }

  os_disk {
    caching              = var.operating_system_disk_cache
    storage_account_type = var.operating_system_disk_type
  }


  }


    # Network Interfaces for Linux VM

resource "azurerm_network_interface" "nic-linux" {
  name                = var.linux_machine_name
  location            = var.location
  resource_group_name = var.resource_group_name
  tags                = var.tags

  ip_configuration {
    name                          = var.ip_configuration_name
    subnet_id                     = azurerm_subnet.subnet.id
    private_ip_address_allocation = var.private_ip_address_allocation
    public_ip_address_id          = azurerm_public_ip.pip-linux.id
  }

  }