Q:

Terraform: Provide credentials for docker hub registry

How would I provide docker hub credentials to a private image in the following example?  
data "docker_registry_image" "ubuntu" {
  name = "ubuntu:latest"
}

resource "docker_image" "ubuntu" {
  name          = "${data.docker_registry_image.ubuntu.name}"
  pull_triggers = ["${data.docker_registry_image.ubuntu.sha256_digest}"]
}

A:

Docker registry credentials is seting up in provider configuration. 
provider "docker" {
  registry_auth {
    address = "quay.io:8181"
    username = "someuser"
    password = "somepass"
  } 
}

Also possible to set env variables DOCKER_REGISTRY_USER and DOCKER_REGISTRY_PASS

