deploy-nixos
============

This is a Terraform module to deploy a NixOS system closure to a
remote machine.

The system closure must be accessible by Nix-importing the repository
root and building a specific attribute
(e.g. `nix-build -A ops.machines.machine-name`).

The target machine must be accessible normally over SSH, and an SSH
key must be used for access.

Notably this module separates the evaluation of the system closure from building
and deploying it, and uses the closure's derivation hash to determine whether a
deploy is necessary.

## Usage example:

```terraform
module "deploy_somehost" {
  source              = "git::https://code.tvl.fyi/depot.git:/ops/terraform/deploy-nixos.git"
  attrpath            = "ops.nixos.somehost"
  target_host         = "somehost.tvl.su"
  target_user         = "someone"
  target_user_ssh_key = tls_private_key.somehost.private_key_pem
}
```

## Future work

Several things can be improved about this module, for example:

* The repository root (relative to which the attribute path is evaluated) could
  be made configurable.

* The remote system closure could be discovered to restore remote system state
  after manual deploys on the target (i.e. "stomping" of changes).

More ideas and contributions are, of course, welcome.

## Acknowledgements

Development of this module was sponsored by [Resoptima](https://resoptima.com/).
