NixOS Installation

NixOS Installation#

Vision#

Capture the NixOS configuration via Nix Flakes. This way it is easy to keep the configuration inside of a Git repository which brings the setup already a few steps closer to a GitOps setup.

Flake overview#

The systems are configured in the Nix Flake. The files are structured in the following way:

  • ./hardware/ - Hardware configurations in the spirit of the flake nixos-hardware.

  • ./machine-classes/ - Configuration for the logical purpose of the machine.

  • ./hosts/ - Configuration of specific hosts including the hostname, network addresses and similar details.

  • ./modules/ - Regular NixOS modules.

Installing the systems#

Automation via Ansible#

There is automation around the cluster deployment available in the folder ansible/ which helps to bring up a cluster of machines. It uses some of the steps described below.

Building the system via nix build#

The system can be built via nix build and then inspected:

nix build .#nixosConfigurations.nixos-test.config.system.build.toplevel

The result is now in the folder ./result.

System installation via nixos-anywhere#

Warning

This will overwrite the current system and set up a fresh NixOS machine. The data on the machine will be lost.

The installation of a machine can be done via nixos-anywhere:

nix run github:nix-community/nixos-anywhere -- --flake .#nixos-test root@192.0.2.1

On a fresh machine boot into the NixOS installer and then set a password for the user root. This should be enough to start with nixos-anywhere.

Development and Hacking#

The machines have the instance flake registered in the flake registry:

flake registry list

Flake based configuration in /etc/nixos/flake.nix:

{
  inputs.my-ops.url = "git+https://git.server.example/infrastructure/my-ops.git?dir=nixos";

  outputs = { self, my-ops }: {
    inherit (my-ops) nixosConfigurations;
  };
}

Useful commands:

nix flake update /etc/nixos

nixos-rebuild build --flake .#my-host

nixos-rebuild switch --flake .#my-host

Rebuilding on a remote target:

nixos-rebuild build --flake .#my-host --target-host root@192.0.2.10

Cloning on the target and rebuilding#

To build on a NixOS machine without copying a dirty working tree, clone the repo on the target and rebuild from a branch:

ssh root@192.0.2.10
git clone https://git.server.example/infrastructure/my-ops.git /root/my-ops
cd /root/my-ops
git checkout my-branch
nixos-rebuild switch --flake .#my-host