Terraform Example: injecting config into an AWS instance

main.tf.js

variable "instance_type" {
  default = "t2.micro"
}

variable "region" {
  default = "us-west-2"
}

variable "custom" {
  default = "env-specific-value"
}

module "ami" {
  source = "github.com/terraform-community-modules/tf_aws_ubuntu_ami/ebs"
  region = "${var.region}"
  distribution = "trusty"
  instance_type = "${var.instance_type}"
}

resource "aws_instance" "web" {
  ami = "${module.ami.ami_id}"
  instance_type = "${var.instance_type}"
  key_name = "tftest"
  connection {
    user = "ubuntu"
    agent = true
  }
  provisioner "remote-exec" {
    inline = [
      "echo ${self.public_ip} | sudo tee /var/run/public_ip",
      "echo ${var.custom} | sudo tee /var/run/custom"
    ]
  }
}