learn-terraform-import: An HCL repository from tharasavio

Learn Terraform Import

Learn what Terraform import is and how to use it.

Follow along with the Learn Guide at HashiCorp Learn.

Install prerequisites

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

Create a docker container

Run this docker command to create a container with the latest nginx image.
```
docker run --name hashicorp-learn --detach --publish 8080:80 nginx:latest
```
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"
```

Import container resource

Initialize your workspace by running terraform init.
Add empty resource stub to docker.tf for the container.
```
resource "docker_container" "web" { }
```

Import the container into Terraform state.

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

Now the container is in your terraform configuration's state.
```
terraform show
```
Run terraform plan. Terraform shows errors for missing required arguments (image, name).
```
terraform plan
```
Generate configuration and save it in docker.tf, replacing the empty resource created earlier.
```
terraform show -no-color > docker.tf
```
Re-run terraform plan.
```
terraform plan
```
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.
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.
Apply the changes. Remember to confirm the run with a yes.
```
terraform apply
```

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
   }
}

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

Verify that your infrastructure still works as expected

$ 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.

Create a Docker image resource

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}}
```

Add the following configuration to your docker.tf file.

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

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

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...

Verify that your configuration matches the current state.
```
terraform apply
```

Manage the container with Terraform

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
  }
}

Apply the change. Remember to confirm the run with a yes.
```
terraform apply
```
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"
```

Destroy resources

Run terraform destroy to destroy the container. Remember to confirm destruction with a yes.
```
terraform destroy
```
Run docker ps to validate that the container was destroyed.
```
docker ps --filter "name=hashicorp-learn"
```

tharasavio/learn-terraform-import