Terraform - Tainting and Updating Resources


We are going to take a look at how to force a redeploy of resources using tainting. This is an extremely useful skill for when parts of a deployment need to be modified.

Tainting and Untainting Resources
Terraform commands:
taint: Manually mark a resource for recreation 
untaint: Manually unmark a resource as tainted

Tainting a resource:

terraform taint [NAME]
Untainting a resource:

terraform untaint [NAME]
Set up the environment:

cd terraform/basics
Redeploy the Ghost image:

terraform apply
Taint the Ghost blog resource:

terraform taint docker_container.container_id
See what will be changed:

terraform plan
Remove the taint on the Ghost blog resource:

terraform untaint docker_container.container_id
Verity that the Ghost blog resource is untainted:

terraform plan
Updating Resources
Let's edit main.tf and change the image to ghost:alpine.

Open main.tf:

vi main.tf
main.tf contents:

# Download the latest Ghost image
resource "docker_image" "image_id" {
  name = "ghost:alpine"
}
# Start the Container
resource "docker_container" "container_id" {
  name  = "ghost_blog"
  image = "${docker_image.image_id.latest}"
  ports {
    internal = "2368"
    external = "80"
  }
}
Validate changes made to main.tf:

terraform validate
See what changes will be applied:

terraform plan
Apply image changes:

terraform apply
List the Docker containers:

docker container ls
See what image Ghost is using:

docker image ls | grep [IMAGE]
Check again to see what changes will be applied:

terraform plan
Apply container changes:

terraform apply
See what image Ghost is now using:

docker image ls | grep [IMAGE]
Cleaning up the environment
Reset the environment:

terraform destroy
Confirm the destroy by typing yes.

List the Docker images:

docker image ls
Remove the Ghost blog image:

docker image rm ghost:latest
Reset main.tf:

vi main.tf
main.tf contents:

# Download the latest Ghost image
resource "docker_image" "image_id" {
  name = "ghost:latest"
}
# Start the Container
resource "docker_container" "container_id" {
  name  = "ghost_blog"
  image = "${docker_image.image_id.latest}"
  ports {
    internal = "2368"
    external = "80"
  }
}
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