Terraform and Nix integration

This repository contains a set of Terraform Modules designed to deploy NixOS machines. These modules are designed to work together and support different deployment scenarios.

What is Terraform?

Terraform is a tool that allows to declare infrastructures as code.

What is Nix, nixpkgs and NixOS?

Nix is a build system and package manager that allows to manage whole system configurations as code. nixpkgs is a set of 20k+ packages built with Nix. NixOS is a Linux distribution built on top of nixpkgs.

What is a Terraform Module?

A Terraform Module refers to a self-contained package of Terraform configurations that are managed as a group. This repo contains a collection of Terraform Modules which can be composed together to create useful infrastructure patterns.

Terraform + Nix vs NixOps

NixOps is a great tool for personal deployments. It handles a lot of things like cloud resource creation, machine NixOS bootstrapping and deployment.

The difficulty is when the cloud resources are not supported by NixOps. It takes a lot of work to map all the cloud APIs. Compared to NixOps, Terraform has become an industry standard and has thousands of people contributing new cloud API mapping all the time.

Another issue is when sharing the configuration as code with multiple developers. Both NixOps and Terraform maintain a state file of "known applied" configuration. Unlike NixOps, Terraform provides facilities to sync and lock the state file so it's available by other users.

The approach here is to use Terraform to create all the cloud resources. By using the google_image_nixos_custom module it's possible to pre-build images in auto-scaling scenarios. Or use a push model similar to NixOps with the generic deploy_nixos module.

So overall Terraform + Nix is more flexible and scales better. But it's also more cumbersome to use as it requires to learn two languages instead of one and the integration between both is also a bit clunky.

Terraform Modules

The list of modules provided by this project:

• deploy_nixos - deploy NixOS onto running NixOS machines
• google_image_nixos - setup an official GCE image into a Google Cloud Project.
• google_image_nixos_custom - build and deploy a custom GCE image into a Google Cloud Project

Using these modules from your terraform configuration

Terraform supports importing modules directly from a GitHub repository.

For example, to use the deploy_nixos module:

module "deploy_nixos" {
  source = "github.com/tweag/terraform-nixos//deploy_nixos?ref=ced68729b6a0382dda02401c8f663c9b29c29368"

  … module-specific fields …
}

Beware the double //, which separates the github repository url from the subdirectory that contains the module. ?ref= specifies a specific git ref of the repository, in this case the commit ced687….

Examples

To better understand how these modules can be used together, look into the ./examples folder.

Related projects

• terraform-provider-nix

Future

• Support other cloud providers.
• Support nixos-infect bootstrapping method.

Contributions are welcome!

Thanks

Thanks to Digital Asset for generously sponsoring this work!

Thanks to Tweag for enabling this work and the continuous support!

License

This code is released under the Apache 2.0 License. Please see LICENSE for more details.

Copyright © 2018 Tweag I/O.