initial commit

README.md

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+# nixos-flake-example
+
+This shows how to build the same config, with and without flakes.
+
+It also shows that `flake.nix` is basically just some syntax.
+
+## overview
+
+Note that these produce the same output:
+
+1. with flakes:
+
+    ```shell
+    nix build '.#nixosConfigurations.mysystem.config.system.build.toplevel'
+    readlink -f result
+    /nix/store/0imi716z1qd04pfh4zdw6mb0gnxmakjs-nixos-system-nixos-21.03.20201020.007126e
+
+    nixos-rebuild build --flake '.#mysystem'
+    readlink -f result
+    /nix/store/0imi716z1qd04pfh4zdw6mb0gnxmakjs-nixos-system-nixos-21.03.20201020.007126e
+    ```
+
+    Note, nixos-rebuild is basically just some magic to build the right derivation
+    and then set it as a system profile, and activate it.
+
+2. without flakes:
+
+    ```shell
+    export NIX_PATH=nixos-config=$(pwd)/configuration.nix:nixpkgs=https://github.com/nixos/nixpkgs/archive/nixos-unstable.tar.gz
+
+
+    /nix/store/zidq625i13hvbbs8alkklj8k6a191xix-nixos-system-nixos-21.03pre-git
+    ```
+
+    **Note**, ~~same path~~ same inner system, just much slower due to no eval cache.
+    (they should be identical, but the flake version suffix is slightly different)
+
+They build the same thing, the flake.nix just moves the redirection from the NixOS channel system
+into the flake instead.
+
+Note, if you come back and run this later, you may need to tell nix to update the `nixpkgs` that it
+has pinned in `flake.lock` by running `nix flake update --update-input nixpkgs`. The non-flake example
+is going to re-download the nixos-unstable build when the cache expires. This could cause any hash differences
+if they're on different revs. (again, another reason to have control of it via flakes, and can lock it directly in the source.)
+

configuration.nix

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+# Edit this configuration file to define what should be installed on
+# your system.  Help is available in the configuration.nix(5) man page
+# and in the NixOS manual (accessible by running ‘nixos-help’).
+
+{ config, pkgs, lib, modulesPath, ... }:
+
+{
+
+  imports = [
+    ./hardware-configuration.nix
+    "${modulesPath}/installer/scan/not-detected.nix"
+
+    # list other modules here
+  ];
+
+  services.sshd.enable = true;
+
+  # etc
+
+}
+

flake.lock

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+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1603153815,
+        "narHash": "sha256-uCav0CJ0Zm0vbqJiS9NUYD4XZg4Ww9bbsFzcDUzh2+U=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "007126eef72271480cb7670e19e501a1ad2c1ff2",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "An example NixOS configuration";
+
+  inputs.nixpkgs = { url = "github:nixos/nixpkgs/nixos-unstable"; };
+
+  outputs = { self, nixpkgs }: {
+    nixosConfigurations = {
+      mysystem = nixpkgs.lib.nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+         (import ./configuration.nix)
+       ];
+      };
+    };
+  };
+}
+

hardware-configuration.nix

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+{ ... }:
+
+{
+    boot.loader.systemd-boot.enable = true; # (for UEFI systems only)
+    fileSystems."/".device = "/dev/disk/by-label/nixos";
+}