machines: add a rescue machine for live-booting

flake.nix

@@ -72,6 +72,7 @@
     machines.desko = decl-bootable-machine { name = "desko"; system = "x86_64-linux"; };
     machines.lappy = decl-bootable-machine { name = "lappy"; system = "x86_64-linux"; };
     machines.moby = decl-bootable-machine { name = "moby"; system = "aarch64-linux"; };
+    machines.rescue = decl-bootable-machine { name = "rescue"; system = "x86_64-linux"; };
   in {
     nixosConfigurations = builtins.mapAttrs (name: value: value.nixosConfiguration) machines;
     imgs = builtins.mapAttrs (name: value: value.img) machines;

machines/rescue/default.nix

@@ -0,0 +1,15 @@
+{ pkgs, ... }:
+{
+  imports = [
+    ./fs.nix
+  ];
+
+  boot.loader.generic-extlinux-compatible.enable = true;
+  boot.loader.efi.canTouchEfiVariables = false;
+  colinsane.image.extraBootFiles = [ pkgs.bootpart-uefi-x86_64 ];
+
+  # TODO: enable root login via ssh
+
+  # docs: https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion
+  system.stateVersion = "21.05";
+}

machines/rescue/fs.nix

@@ -0,0 +1,13 @@
+{ ... }:
+
+{
+  # root is a tmpfs so that we have an ephemeral system ("impermanence" handles the state)
+  fileSystems."/" = {
+    device = "/dev/disk/by-uuid/44445555-6666-7777-8888-999900001111";
+    fsType = "ext4";
+  };
+  fileSystems."/boot" = {
+    device = "/dev/disk/by-uuid/2222-3333";
+    fsType = "vfat";
+  };
+}