04_data_sources.adoc

Data sources

In the main.tf we hardcoded the ami (the image id). This is not a good practice. We should use data object to get the ami and instance type dynamically.

It is possible to get the ami id dynamically using the aws_ami data object in terraform:

data "aws_ami" "ubuntu" {
  most_recent = true

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-amd64-server-*"]
  }

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

  owners = ["099720109477"] # Canonical
}

In this example, we are using the aws_ami data object to get the most recent Ubuntu 22.04 image id. We are using the most_recent attribute to get the most recent image id. We are using the filter attribute to filter the image id based on the name and virtualization-type. We are using the owners attribute to specify the owner of the image id.

We can use the data object in the resource block to get the ami id dynamically:

resource "aws_instance" "example" {
  ami           = data.aws_ami.ubuntu.id
  instance_type = "t2.micro"
}

In this example, we are using the data object to get the ami id dynamically. We are using the id attribute to get the ami id.

Task: Use data object to get the ami id dynamically

• Now modify your main.tf file to use the data object to get the ami id dynamically.

• Run terraform plan to review the changes

• And then run terraform apply to apply the changes

Next step: Variables