Terraform by Example

Data Sources

A data source, also known as data resources, allows Terraform to fetch and use information from resources defined outside Terraform or managed by a different Terraform configuration.

A data resource also supports count and for_each arguments.

A data resource must be defined using a data block like the example below:

data "aws_iam_role" "example" {
  name = "role_name"

Using Data sources to fetch information #

Data sources can be used to fetch resources created by other Terraform configurations, like a VPC. Here we are fetching a Google VPC, so we can use it to define a redis instance.

data "google_compute_network" "redis-network" {
  name = "existing-vpc"

resource "google_redis_instance" "cache" {
  name           = "memory-cache"
  memory_size_gb = 1
  authorized_network = data.google_compute_network.redis-network.id

Data sources can also be used to fetch information not managed by Terraform, below is an example of a data source fetching an ubuntu AWS AMI, so we pass the AMI ID and create an ubuntu instance in AWS.

data "aws_ami" "ubuntu" {
  most_recent = true

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"]

  filter {
    name   = "virtualization-type"
    values = ["hvm"]

  owners = ["099720109477"] # Canonical account ID

resource "aws_instance" "web" {
  ami           = data.aws_ami.ubuntu.id
  instance_type = "t3.micro"

  tags = {
    Name = "MyWebInstance"

Want to learn more about data sources? Check out the docs.