make extlinux work with liminix-rebuild

add /boot to the systemConfiguration closure

examples/rotuer.nix

@@ -44,11 +44,12 @@ in rec {
     ../modules/ntp
     ../modules/ssh
     ../modules/outputs/btrfs.nix
-
+    ../modules/outputs/extlinux.nix
   ];
   hostname = "rotuer";
   rootfsType = "btrfs";
   rootOptions = "subvol=@";
+  boot.loader.extlinux.enable = true;
 
   services.hostap = svc.hostapd.build {
     interface = config.hardware.networkInterfaces.wlan;

modules/outputs/extlinux.nix

@@ -6,6 +6,7 @@
 }:
 let
   inherit (lib) mkIf mkEnableOption mkOption types concatStringsSep;
+  inherit (pkgs.pseudofile) dir symlink;
   cfg = config.boot.loader.extlinux;
   o = config.system.outputs;
   cmdline = concatStringsSep " " config.boot.commandLine;
@@ -17,7 +18,7 @@ in {
   };
   options.boot.loader.extlinux.enable = mkEnableOption "extlinux";
 
-  config =  { # mkIf cfg.enable {
+  config = mkIf cfg.enable {
     system.outputs.extlinux = pkgs.runCommand "extlinux" {} ''
       mkdir $out
       cd $out
@@ -27,7 +28,7 @@ in {
       mkdir extlinux
       cat > extlinux/extlinux.conf << _EOF
       menu title Liminix
-      timeout 100
+      timeout 40
       label Liminix
         kernel /boot/kernel
         # initrd /boot/initramfs
@@ -35,5 +36,8 @@ in {
         ${if wantsDtb then "fdt /boot/dtb" else ""}
       _EOF
     '';
+    filesystem = dir {
+      boot = symlink config.system.outputs.extlinux;
+    };
   };
 }

pkgs/systemconfig/default.nix

@@ -84,8 +84,19 @@ in attrset:
       #!/bin/sh -e
       prefix=\''${1-/}
       src=\''${prefix}$out
-      mkdir -p \$prefix/persist
-      cp -v -fP \$src/bin/* \$src/etc/* \$prefix/persist
+      dest=\$prefix
+      ${# if we are running on a normal mounted system then
+        # the actual device root is mounted on /persist
+        # and /nix is bind mounted from /persist/nix
+        # (see the code in preinit). So we need to check for this
+        # case otherwise we will install into a ramfs/rootfs
+        ""
+      }
+      if test -d $dest/persist; then dest=$dest/persist; fi
+      cp -v -fP \$src/bin/* \$src/etc/* \$dest
+      ${if attrset ? boot then ''
+        (cd \$prefix && rm ./boot && ln -sf ${lib.strings.removePrefix "/" attrset.boot.target} ./boot)
+      '' else ""}
       EOF
       chmod +x $out/bin/install
     '';