Change infrastructure

4min
|
Terraform

In the previous tutorial, you created your first infrastructure with Terraform: a resource group. Now you will modify your configuration by defining an additional resource that references your resource group and adding tags to your resource group.

Note

This tutorial builds on configuration from a previous tutorial. If you have not yet completed it, do so now.

Create a new resource

In your main.tf file, add the resource block below to create a virtual network (VNet).

main.tf

# Create a virtual network
resource "azurerm_virtual_network" "vnet" {
  name                = "myTFVnet"
  address_space       = ["10.0.0.0/16"]
  location            = "westus2"
  resource_group_name = azurerm_resource_group.rg.name
}

To create a new Azure VNet, you have to specify the name of the resource group to contain the VNet. By referencing the resource group, you establish a dependency between the resources. Terraform ensures that resources are created in proper order by constructing a dependency graph for your configuration.

Apply your changes

After changing the configuration, run terraform apply again to see how Terraform will apply this change to your infrastructure. Respond yes to the prompt to confirm the changes.

$ terraform apply
azurerm_resource_group.rg: Refreshing state... [id=/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  # azurerm_virtual_network.vnet will be created
  + resource "azurerm_virtual_network" "vnet" {
      + address_space         = [
          + "10.0.0.0/16",
        ]
      + guid                  = (known after apply)
      + id                    = (known after apply)
      + location              = "westus2"
      + name                  = "myTFVnet"
      + resource_group_name   = "myTFResourceGroup"
      + subnet                = (known after apply)
      + vm_protection_enabled = false
    }

Plan: 1 to add, 0 to change, 0 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

azurerm_virtual_network.vnet: Creating...
azurerm_virtual_network.vnet: Creation complete after 6s [id=/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup/providers/Microsoft.Network/virtualNetworks/myTFVnet]

Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

Terraform builds an execution plan by comparing your desired state as described in the configuration to the current state, which is saved in either the local terraform.tfstate file or in a remote state backend depending on your configuration.

Modify an existing resource

In addition to creating new resources, Terraform can modify existing resources.

Open your main.tf file. Update the azurerm_resource_group resource in your configuration by adding the tags block as shown below:

Tip

The below snippet is formatted as a diff to give you context about what in your configuration should change. Add the content in green (exclude the leading + sign).

main.tf

resource "azurerm_resource_group" "rg" {
  name     = "myTFResourceGroup"
  location = "westus2"

  tags = {
    Environment = "Terraform Getting Started"
    Team = "DevOps"
  }
}

Apply your changes

Run terraform apply to modify your infrastructure. Respond yes to the prompt to confirm the operation.

$ terraform apply
azurerm_resource_group.rg: Refreshing state... [id=/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup]
azurerm_virtual_network.vnet: Refreshing state... [id=/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
  ~ update in-place

Terraform will perform the following actions:

  # azurerm_resource_group.rg will be updated in-place
  ~ resource "azurerm_resource_group" "rg" {
        id       = "/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup"
        name     = "myTFResourceGroup"
      ~ tags     = {
          + "Environment" = "Terraform Getting Started"
          + "Team"        = "DevOps"
        }
        # (1 unchanged attribute hidden)
    }

Plan: 0 to add, 1 to change, 0 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

azurerm_resource_group.rg: Modifying... [id=/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup]
azurerm_resource_group.rg: Modifications complete after 1s [id=/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup]

Apply complete! Resources: 0 added, 1 changed, 0 destroyed.

The prefix ~ means that Terraform will update the resource in-place.

Review updates to state

Use terraform show again to see the new values associated with this resource group.

$ terraform show
# azurerm_resource_group.rg:
resource "azurerm_resource_group" "rg" {
    id       = "/subscriptions/c9ed8610-47a3-4107-a2b2-a322114dfb29/resourceGroups/myTFResourceGroup"
    location = "westus2"
    name     = "myTFResourceGroup"
    tags     = {
        "Environment" = "Terraform Getting Started"
i       "Team"        = "DevOps"
    }
}
##...

Run terraform state list to get the updated list of resources managed in your workspace.

$ terraform state list
azurerm_resource_group.rg
azurerm_virtual_network.vnet

Build

Destroy