Effect Infrastructure

• Getting Started
  • Prerequisites
• Directory Structure
  • NixOS
    • Home Manager
    • Modules
  • Terraform
    • Bootstrapping
    • GitHub
  • Troubleshooting
• Secret Management
  • Updating Secrets
  • NixOS
  • Terraform
  • Adding a Public Key

Getting Started

Prerequisites

This project works best if the following tools are installed:

• Nix
• direnv

If you use nix and direnv on your host machine, then all required tooling and packages will be automatically installed for you in your development shell.

In addition, this project uses pre-commit. If you are not using Nix + direnv, you can install the Git hooks manually in your project by installing pre-commit and running:

pre-commit install

Directory Structure

NixOS

The directory structure of this project is optimized for sharing configuration as much as possible.

The /hosts directory contains all systems that are managed by NixOS. Each host has its own directory (with the same name as the machine's hostname).

In addition, the /hosts directory contains a /common subdirectory. This directory contains configuration that can be shared across all hosts. Within the /common subdirectory, we have the following:

• /common/global -> global configuration that is shared between all hosts
• /common/presets -> presets that are applied to specific host types (i.e. nixos, darwin, desktop, etc.)
• /common/users -> user-specific configuration that is shared between hosts

Home Manager

The /home directory contains per-user, per-host Home Manager configurations. The directory hierarchy corresponds to the user-specific Home Manager configurations for a particular host.

/home/<username>/<hostname>

In addition, the /home directory contains a /common subdirectory. This directory contains Home Manager configurations that can be shared across all hosts. Within the /common subdirectory, we have the following:

• /common/global -> global configuration that is shared between all hosts
• /common/presets -> presets that are applied to specific host types (i.e. nixos, darwin, desktop, etc.)

Modules

The /modules directory contains shared NixOS and Home Manager modules.

Terraform

For infrastructure that is unable to be maintained by Nix (i.e. external services such as GitHub), we leverage HashiCorp Terraform.

Bootstrapping

You can provision the infrastructure in AWS required to host Terraform state using the boostrap.sh script:

./terraform/scripts/bootstrap.sh --bucket <bucket-name> --region <aws-region> --table <dynamodb-table>

GitHub

cd terraform/github
terraform init
terraform plan

Troubleshooting

To lock provider versions for different operating systems / architectures:

terraform providers lock -platform=linux_amd64 -platform=darwin_amd64 -platform=linux_arm64 -platform=darwin_arm64

Secret Management

This project makes use of Mozilla SOPS (Secrets OPerationS)

The .sops.yaml file at the root of the repository defines creation rules for secrets to be encrypted with sops. Any files matching the defined creation rule paths will be encrypted with the specified public keys.

Updating Secrets

To update secret files after making changes to the .sops.yaml file, run the snippet below:

find . -regex $(yq -r '[.creation_rules[] | "./" + .path_regex] | join("\\|")' "$(pwd)/.sops.yaml") | \
xargs -i sops updatekeys -y {}

NixOS

The project uses sops-nix for automatically decrypting and injecting secrets into our NixOS configurations.

Terraform

The project uses the [carlpett/sops] Terraform provider for automatically decrypting and injecting secrets into our Terraform configurations.

Adding a Public Key

The easiest way to add new machines is by using SSH host keys (this requires OpenSSH to be enabled).

We use age to encrypt secrets. To obtain an age public key, you can use the ssh-to-age tool to convert a host SSH Ed25519 key to the age format.

nix run nixpkgs#ssh-to-age -- ssh-to-age < /etc/ssh/ssh_host_ed25519_key.pub

Then add the age public key to the .sops.yaml file, apply it to the desired key groups, and then re-encrypt the secret files (see Updating Secrets).