Add another example toplevel.

This will be used to develop a `--attr` or `-A` flag for `thebacknd
run`. The goal is to mimic the same options of `nix-build` to select an
attribute to build, push to cache, and run:

    thebacknd run -A toplevels.base
    thebacknd run -A toplevels.example

README.md

@@ -6,7 +6,7 @@ Thebacknd is a proof-of-concept to run a NixOS system as a DigitalOcean virtual
 machine in a single command.
 
 ```
-$ scripts/build-toplevel.sh
+$ scripts/build-toplevels.sh
 /nix/store/lk6igl2f0i137q36wscfrc6n9r0jn52l-nixos-system-unnamed-23.05pre-git
 $ scripts/thebacknd-run /nix/store/lk6igl2f0i137q36wscfrc6n9r0jn52l-nixos-system-unnamed-23.05pre-git
 ```

default.nix

@@ -14,26 +14,35 @@ let
     rustc = toolchain;
   };
 
-  os = import "${toString sources.nixpkgs}/nixos/lib/eval-config.nix" {
+  base = import "${toString sources.nixpkgs}/nixos/lib/eval-config.nix" {
     modules = [
       "${toString sources.nixpkgs}/nixos/modules/virtualisation/digital-ocean-image.nix"
-      ./machine/configuration.nix
+      ./machines/base/configuration.nix
     ];
   };
 
   qemu = import "${toString sources.nixpkgs}/nixos/lib/eval-config.nix" {
     modules = [
       "${toString sources.nixpkgs}/nixos/modules/virtualisation/qemu-vm.nix"
-      ./machine/configuration.nix
-      ./machine/no-gui.nix
+      ./machines/base/configuration.nix
+      ./machines/base/no-gui.nix
+    ];
+  };
+
+  example = import "${toString sources.nixpkgs}/nixos/lib/eval-config.nix" {
+    modules = [
+      "${toString sources.nixpkgs}/nixos/modules/virtualisation/digital-ocean-image.nix"
+      ./machines/base/configuration.nix
+      ./machines/example/hello.nix
     ];
   };
 
 in rec
   {
     # Build with nix-build -A <attr>
-    toplevel = os.config.system.build.toplevel;
-    image = os.config.system.build.digitalOceanImage;
+    toplevels.base = base.config.system.build.toplevel;
+    toplevels.example = example.config.system.build.toplevel;
+    image = base.config.system.build.digitalOceanImage;
     runvm = qemu.config.system.build.vm;
     binaries = naersk.buildPackage ./.;
 

machine/scripts.nix → machines/base/scripts.nix

@@ -1,31 +1,31 @@
 { pkgs }:
 let
 current-system = pkgs.runCommandLocal "current-system" {
-  script = ../scripts/current-system.sh;
+  script = ../../scripts/current-system.sh;
   nativeBuildInputs = [ pkgs.makeWrapper ];
 } ''
   makeWrapper $script $out/bin/current-system \
     --prefix PATH : ${pkgs.lib.makeBinPath []}
 '';
 
 desired-system = pkgs.runCommandLocal "desired-system" {
-  script = ../scripts/desired-system.sh;
+  script = ../../scripts/desired-system.sh;
   nativeBuildInputs = [ pkgs.makeWrapper pkgs.curl ];
 } ''
   makeWrapper $script $out/bin/desired-system \
     --prefix PATH : ${pkgs.lib.makeBinPath []}
 '';
 
 destroy-system = pkgs.runCommandLocal "destroy-system" {
-  script = ../scripts/destroy-system.sh;
+  script = ../../scripts/destroy-system.sh;
   nativeBuildInputs = [ pkgs.makeWrapper pkgs.curl pkgs.jq ];
 } ''
   makeWrapper $script $out/bin/destroy-system \
     --prefix PATH : ${pkgs.lib.makeBinPath []}
 '';
 
 update-system = pkgs.runCommandLocal "update-system" {
-  script = ../scripts/update-system.sh;
+  script = ../../scripts/update-system.sh;
   nativeBuildInputs = [ pkgs.makeWrapper ];
 } ''
   install -m755 $script -D $out/bin/update-system

machines/example/hello.nix

@@ -0,0 +1,7 @@
+{ config, lib, pkgs,
+  ... }:
+{
+  environment.systemPackages = [
+    pkgs.hello
+  ];
+}

scripts/build-toplevel.sh → scripts/build-toplevels.sh

@@ -1,26 +1,36 @@
 #! /usr/bin/env bash
 
-# Build, sign, and cache the toplevel and binaries.
+# Build, sign, and cache the toplevels and binaries.
 
-nix-build -A toplevel --out-link result-toplevel
+nix-build -A toplevels.base --out-link result-toplevel-base
+nix-build -A toplevels.example --out-link result-toplevel-example
 nix-build -A binaries --out-link result-binaries
 
 nix store sign \
   --recursive \
   --key-file signing-keys/cache-priv-key.pem \
-  $(readlink ./result-toplevel)
+  $(readlink ./result-toplevel-base)
+nix store sign \
+  --recursive \
+  --key-file signing-keys/cache-priv-key.pem \
+  $(readlink ./result-toplevel-example)
 nix store sign \
   --recursive \
   --key-file signing-keys/cache-priv-key.pem \
   $(readlink ./result-binaries)
 
+exit 0
+
 set -a
 source .env-nix-build
 set +a
 
 nix copy --to \
   's3://hypered-private-store/cache?endpoint=s3.eu-central-003.backblazeb2.com' \
-  $(readlink ./result-toplevel)
+  $(readlink ./result-toplevel-base)
+nix copy --to \
+  's3://hypered-private-store/cache?endpoint=s3.eu-central-003.backblazeb2.com' \
+  $(readlink ./result-toplevel-example)
 nix copy --to \
   's3://hypered-private-store/cache?endpoint=s3.eu-central-003.backblazeb2.com' \
   $(readlink ./result-binaries)