modules/image: distribute systemd-boot loader configs

modules/image.nix

@@ -106,6 +106,7 @@ in
         dosfstools
         libfaketime
         mtools
+        rsync
       ];
       partitionID = vfatUuidFromFs bootFs;
       size = cfg.bootPartSize;
@@ -124,7 +125,7 @@ in
         echo "installing extraBootFiles"
         for d in ${lib.escapeShellArgs cfg.extraBootFiles}; do
           echo "installing '$d'"
-          cp -R $d/* ./
+          rsync -arv $d/ ./
         done
         echo "copied extraBootFiles"
       )
@@ -382,11 +383,50 @@ in
       ''
     );
 
-    # TODO: generalize this beyond just `generic-extlinux-compatible`. use `system.build.installBootLoader`?
-    sane.image.extraBootFiles = lib.optionals config.boot.loader.generic-extlinux-compatible.enable [
-      (pkgs.runCommandLocal "populate-extlinux" {} ''
-        ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d "$out"
-      '')
-    ];
+    sane.image.extraBootFiles =
+      lib.optionals config.boot.loader.generic-extlinux-compatible.enable [
+        (pkgs.runCommandLocal "populate-extlinux" {} ''
+          ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d "$out"
+        '')
+      ]
+      ++
+      lib.optionals config.boot.loader.systemd-boot.enable [
+        # it'd be cool to use `config.system.build.installBootLoader` to install both the bootloader config AND the bootloader itself,
+        # but the combination of custom nixpkgs logic + systemd's sanity checking makes it near impossible to use
+        # outside a live system.
+        # so manually generate a bootloader entry:
+        (pkgs.runCommandLocal "populate-systemd-boot" {} ''
+          toplevel=${config.system.build.toplevel}
+          kernel_params=$(cat "$toplevel/kernel-params")
+
+          kernel=$(readlink "$toplevel/kernel")
+          kernel_name="''${kernel/\/nix\/store\//}"
+          kernel_name="''${kernel_name/\//-}"
+          efi_kernel="/EFI/nixos/$kernel_name.efi"
+          install -Dm644 "$kernel" "$out/$efi_kernel"
+
+          initrd=$(readlink "$toplevel/initrd")
+          initrd_name="''${initrd/\/nix\/store\//}"
+          initrd_name="''${initrd_name/\//-}"
+          efi_initrd="/EFI/nixos/$initrd_name.efi"
+          install -Dm644 "$initrd" "$out/$efi_initrd"
+
+          mkdir -p $out/loader/entries
+          cat > $out/loader/entries/nixos-generation-0.conf <<EOF
+            title NixOS
+            sort-key nixos
+            version Generation 0 NixOS
+            linux $efi_kernel
+            initrd $initrd
+            options init=$toplevel/init $kernel_params
+          EOF
+          cat > $out/loader/loader.conf <<EOF
+            timeout 5
+            default nixos-generation-0.conf
+            console-mode keep
+          EOF
+        '')
+      ]
+    ;
   };
 }