Learn how to import existing resources under Terraform's management.

Follow along with the Learn Terraform Import tutorial.

1. Terraform: https://www.terraform.io/downloads.html
2. Docker: https://docs.docker.com/get-docker/

1. Run this docker command to create a container with the latest nginx image.

   docker run --name hashicorp-learn --detach --publish 8080:80 nginx:latest

2. Verify container is running by running docker ps or visiting 0.0.0.0:8080 in your web browser.

   docker ps --filter "name=hashicorp-learn"

1. Initialize your workspace by running terraform init.

2. Add empty resource stub to docker.tf for the container.

   resource "docker_container" "web" { }

3. Import the container into Terraform state.

   terraform import docker_container.web $(docker inspect -f {{.ID}} hashicorp-learn)

4. Now the container is in your terraform configuration's state.

   terraform show

5. Run terraform plan. Terraform shows errors for missing required arguments (image, name).

   terraform plan

6. Generate configuration and save it in docker.tf, replacing the empty resource created earlier.

   terraform show -no-color > docker.tf

7. Re-run terraform plan.

   terraform plan

8. Terraform will show warnings and errors about a deprecated attribute (links), and several read-only attributes (ip_address, network_data, gateway, ip_prefix_length, id). Remove these attributes from docker.tf.

9. Re-run terraform plan.

   terraform plan

   It should now execute successfully. The plan indicates that Terraform will update in place to add the attach, logs, must_run, and start attributes. Notice that the container resource will not be replaced.

10. Apply the changes. Remember to confirm the run with a yes.

    terraform apply

11. There are now several attributes in docker.tf that are unnecessary because they are the same as their default values. After removing these attributes, docker.tf will look something like the following.

    # docker_container.web:
    resource "docker_container" "web" {
       name  = "hashicorp-learn"
       image = "sha256:9beeba249f3ee158d3e495a6ac25c5667ae2de8a43ac2a8bfd2bf687a58c06c9"
    
       ports {
           external = 8080
           internal = 80
       }
    }

12. Run terraform plan again to verify that removing these attributes did not change the configuration.

    terraform plan

$ docker ps --filter "name=hashicorp-learn"

You can revisit `0.0.0.0:8080` in your web browser to verify that it is
still up. Also note the "Status" - the container has been up and running
since it was created, so you know that it was not restarted when you
imported it into Terraform.

1. Retrieve the image's tag name by running the following command, replacing the sha256 value shown with the one from docker.tf.

   docker image inspect sha256:602e111c06b6934013578ad80554a074049c59441d9bcd963cb4a7feccede7a -f {{.RepoTags}}

2. Add the following configuration to your docker.tf file.

   resource "docker_image" "nginx" {
     name = "nginx:latest"
   }

3. Run terraform apply to apply the changes. Remember to confirm the run with a yes.

   terraform apply

4. Now that Terraform has created a resource for the image, refer to it in docker.tf like so:

   resource "docker_container" "web" {
     name  = "hashicorp-learn"
     image = docker_image.nginx.latest
   
   # File truncated...

5. Verify that your configuration matches the current state.

   terraform apply

1. In your docker.tf file, change the container's external port from 8080 to 8081.

   resource "docker_container" "web" {
     name  = "hashicorp-learn"
     image = "sha256:602e111c06b6934013578ad80554a074049c59441d9bcd963cb4a7feccede7a5"
   
     ports {
       external = 8081
       internal = 80
     }
   }

2. Apply the change. Remember to confirm the run with a yes.

   terraform apply

3. Verify that the new container works by running docker ps or visiting 0.0.0.0:8081 in your web browser.

   docker ps --filter "name=hashicorp-learn"

1. Run terraform destroy to destroy the container. Remember to confirm destruction with a yes.

   terraform destroy

2. Run docker ps to validate that the container was destroyed.

   docker ps --filter "name=hashicorp-learn"