How to force delete Docker image with terraform destroy

Question

I was following a tutorial on terraform.io that has me provision a docker image and container using terraform, and then destroy the terraform stack. However, I get the following error:

Error: Unable to remove Docker image: 
Error response from daemon: conflict: unable to delete 540a289bab6c (must be forced) - 
image is being used by stopped container ae12197d265d

I know the native Docker solution to this is just running docker rmi -f 540a289bab6c. However, I was wondering if there's a terraform approach to this?

The docs for the terraform resource docker_image show the reason terraform attempted to destroy the image upon terraform destroy: the template main.tf had keep-locally set to true. But it doesn't say how to force that destruction.

The main.tf from the tutorial is as follows:

terraform {
  required_providers {
    docker = {
      source = "terraform-providers/docker"
    }
  }
}

provider "docker" {}

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

resource "docker_container" "nginx" {
  image = docker_image.nginx.latest
  name  = "tutorial"
  ports {
    internal = 80
    external = 8000
  }
}

So how do I force terraform destroy to work on this template without resorting to manual intervention using docker native tools?

Answer 1

The error message indicates that there is another container relying on the same image. It could be that a separate docker container provisioned outside of terraform and using the same nginx docker image in the tutorial. Check your docker ps -a to see if there is such container if so just run docker rm -f <container_name>to remove it and your terraform destroy should work.