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Generating a Ansible Inventory File from Terraform ​

Overview ​

Often when working with automated deployments you will want to generate a dynamic inventory file for Ansible (usually after your infrastructure has been provisioned). This is a simple snippet to generate an inventory file from Terraform.

Terraform Snippet ​

First we need to create an ouput variable to hold the inventory file.

hcl
output "ansible_inventory_yml" {
  description = "An Ansible inventory (in YAML format) containing IP addresses as required by the Ansible playbook to configure the servers."
  value = local.ansible_inventory_yml
}

Next we will create the local variable that will hold the inventory file.

INFO

In this example we are using a DigitalOcean droplet, but you can use any Terraform resource that has an IP address.

hcl
locals {
  ansible_inventory_yml = <<-EOF
    all:
      hosts:
        app:
          ansible_host: ${digitalocean_droplet.server.ipv4_address}
  EOF
}

TIP

It's better to use a local and output variable rather then a local_file as this avoids spurious plan noise when running on CI runners.

Once all configured you can run terraform apply and the inventory file will be ouput to the console. To create the file you can pipe the output to a file (either in the console or in your CI pipeline).

bash
terraform output -raw ansible_inventory_yml > ansible-inventory.yml