Back to Lab Index

Lab description

In this lab we learn about the import block and data sources in Terraform.

Import existing resources and read data from external resources

Setup

Make sure you are in the correct folder:

1

cd ~/terraform-labs

1

cd ~/terraform-labs

If you were unable to complete the last lab, you can find a copy of the files in the solutions folder

1. Create some resource groups using azure portal or cli in “UK South”

  1. Create a couple of resource groups outside of terraform.

    1
2

     az group create --name temp_rg1 --location "UK South"
 az group create --name temp_rg2 --location "UK South"

    1
2

     az group create --name temp_rg1 --location "UK South"
 az group create --name temp_rg2 --location "UK South"

  2. Verify that the resource group is created

  3. Append below code into main.tf (we are trying to create same resource group via terraform)

    We are also using a data block, so we can retrieve the id of temp_rg2 resource group.

    1
2
3
4
5
6
7
8
9
10
11
12

     resource "azurerm_resource_group" "temp_resource_group_1" {
   name     = "temp_rg1"
   location = "UK South"
    
   tags = {
     reference = data.azurerm_resource_group.temp_resource_group_2.id
   }
 }
    
 data "azurerm_resource_group" "temp_resource_group_2" {
   name = "temp_rg2"
 }

2. Plan

  1. Run a plan

    1

     terraform plan

    1

     terraform plan

  2. You should see something like below where terraform thinks temp_rg1 is a new resource

    1
2
3
4
5
6
7
8
9
10
11
12
13

     Terraform will perform the following actions:
    
   # azurerm_resource_group.temp_resource_group_1 will be created
   + resource "azurerm_resource_group" "temp_resource_group_1" {
       + id       = (known after apply)
       + location = "uksouth"
       + name     = "temp_rg1"
       + tags     = {
           + "reference" = "/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg2"
         }
     }
    
 Plan: 1 to add, 0 to change, 0 to destroy.

Data Source - Also note that we are able to refer the id of temp_rg2 resource group without any issues. This is because we are not trying to manage that resource, but only retrieving some details about it.

3. Apply (and observe the error)

  1. Run an apply.

    1

     terraform apply -auto-approve

    1

     terraform apply -auto-approve

  2. Review the error

    1
2
3
4
5

     │ Error: A resource with the ID "/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg1" already exists - to be managed via Terraform this resource needs to be imported into the State. Please see the resource documentation for "azurerm_resource_group" for more information.
 │
 │   with azurerm_resource_group.temp_resource_group_1,
 │   on main.tf line 25, in resource "azurerm_resource_group" "temp_resource_group_1":
 │   25: resource "azurerm_resource_group" "temp_resource_group_1" {

    This is because terraform wasn’t aware of this resource until it tried an apply.

3. Import

  1. Add the following import block to main.tf to import the resource group.

    Be sure to replace <subscription-id> with your subscription id.

    1
2
3
4

     import {
   to = azurerm_resource_group.temp_resource_group_1
   id = "/subscriptions/<subscription-id>/resourceGroups/temp_rg1"
 }

  2. Run the apply again

    1

     terraform apply -auto-approve

    1

     terraform apply -auto-approve

    NOTE: An alternative approach is to use the CLI command terraform import azurerm_resource_group.temp_resource_group_1 "/subscriptions/<subscription_id>/resourceGroups/temp_rg"

  3. You should see an output such as below

    1
2
3
4
5
6
7

     Plan: 1 to import, 0 to add, 1 to change, 0 to destroy.
 azurerm_resource_group.temp_resource_group_1: Importing... [id=/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg1]
 azurerm_resource_group.temp_resource_group_1: Import complete [id=/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg1]
 azurerm_resource_group.temp_resource_group_1: Modifying... [id=/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg1]
 azurerm_resource_group.temp_resource_group_1: Modifications complete after 1s [id=/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg1]
    
 Apply complete! Resources: 1 imported, 0 added, 1 changed, 0 destroyed.

  4. Run apply again to ensure there are no changes.

    1

     terraform apply -auto-approve

    1

     terraform apply -auto-approve

  5. Remove the import block and apply again.

    Delete the import block from main.tf and run an apply.

    1

     terraform apply -auto-approve

    1

     terraform apply -auto-approve

4. Check state

Run a terraform show. The “temp_rg” resource group should now appear in the output as well.

1

terraform show

1

terraform show

5. Remove the resource block

  1. Remove the resource and data block we added for temp_resource_group_1 from main.tf

    main.tf should just look just like below. (as it was before we started this lab)

    1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

     terraform {
   required_providers {
     azurerm = {
       source  = "hashicorp/azurerm"
       version = "~> 4.0"
     }
   }
 }
    
 provider "azurerm" {
   features {}
 }
    
 locals {
   subnets = cidrsubnets("10.0.0.0/24", 6, 7, 8)
 }
    
 resource "azurerm_resource_group" "demo" {
   for_each = var.resource_groups
   name     = "${var.prefix}_${each.value}"
   location = var.region
   tags     = var.tags
 }

6. Plan and apply

  1. Run a plan and apply to delete temp_rg1
1

  terraform apply

1

  terraform apply
  1. Check the plan is showing it will destroy temp_rg1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

  Terraform will perform the following actions:
  
    # azurerm_resource_group.temp_resource_group_1 will be destroyed
    # (because azurerm_resource_group.temp_resource_group_1 is not in configuration)
    - resource "azurerm_resource_group" "temp_resource_group_1" {
        - id         = "/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg1" -> null
        - location   = "uksouth" -> null
        - name       = "temp_rg1" -> null
        - tags       = {
            - "reference" = "/subscriptions/b857908d-3f5c-4477-91c1-0fbd08df4e88/resourceGroups/temp_rg2"
          } -> null
          # (1 unchanged attribute hidden)
      }
  
  Plan: 0 to add, 0 to change, 1 to destroy.
  1. Enter yes to run thye apply

7. Verify that temp_rg is deleted

  1. Check the portal or cli to ensure temp_rg1 is deleted.
  2. Run a terraform show to ensure it’s gone from state file as well.
Back to Lab Index