variable "foo" { default = "bar"; description = "bar"; } provider "aws" { access_key = "foo"; secret_key = "bar"; } provider "do" { api_key = "${var.foo}"; } resource "aws_security_group" "firewall" { count = 5 } resource aws_instance "web" { ami = "${var.foo}" security_groups = [ "foo", "${aws_security_group.firewall.foo}" ] network_interface { device_index = 0 description = "Main network interface" } } resource "aws_instance" "db" { security_groups = "${aws_security_group.firewall.*.id}" } output "web_ip" { value = "${aws_instance.web.private_ip}" }