[raspberry] add base image

i currently try building it and then check if it works

README.md

@@ -53,6 +53,22 @@ to build a configuration run the following command (replace ```<hostname>``` wit
 nix build .#nixosConfigurations.<hostname>.config.system.build.toplevel
 ```
 
+### building raspberry image
+
+for the raspberry it is possible to build the whole configuration as an sd-card image which then can be flashed directly. more information about building arm on nixos can be found [here](https://nixos.wiki/wiki/NixOS_on_ARM).
+
+to be able to build the image you need to enable qemu emulation on the machine you are building with. therefore it is necessary to add the following to your configuration.nix:
+
+``` nix
+boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
+```
+
+then you can build the image with:
+
+``` shell
+nix build .#nixosConfigurations.rpi1_base_image.config.system.build.sdImage
+```
+
 ### run a configuration as vm
 
 to run a vm we have to build it first using the following command (replace ```<hostname>``` with the actual hostname):

machines/configuration.nix

@@ -36,4 +36,21 @@ in
       ./moderatio/configuration.nix
     ];
   };
+
+  rpi1_base_image = nixosSystem {
+    system = "aarch64-linux";
+    modules = [
+      "${nixpkgs}/nixos/modules/installer/sd-card/sd-image-raspberrypi.nix"
+      ./modules/sshd.nix
+      {
+        nixpkgs.config.allowUnsupportedSystem = true;
+        nixpkgs.crossSystem.system = "aarch64-linux";
+
+        networking.hostName = "rp1_base_image";
+        networking.networkmanager.enable = true;
+
+        system.stateVersion = "22.05";
+      }
+    ];
+  };
 }

outputs.nix

@@ -17,8 +17,10 @@ in (utils.lib.eachSystem (builtins.filter filter_system utils.lib.defaultSystems
     devShells.default = pkgs.callPackage ./shell.nix {
       inherit (sops-nix.packages."${pkgs.system}") sops-import-keys-hook ssh-to-pgp sops-init-gpg-key;
     };
-  })) // {
+  })) // rec {
     nixosConfigurations = import ./machines/configuration.nix (inputs // {
       inherit inputs;
     });
+
+    images.rpi1_base_image = nixosConfigurations.rpi1_base_image.config.system.build.sdImage;
 }