Refactor common unionfs-fuse initrd prep into a separate module

modules/installer/cd-dvd/iso-image.nix

@@ -194,25 +194,14 @@ in
 
   boot.initrd.availableKernelModules = [ "squashfs" "iso9660" ];
 
-  boot.initrd.kernelModules = [ "loop" "fuse" ];
+  boot.initrd.kernelModules = [ "loop" ];
 
   boot.kernelModules = pkgs.stdenv.lib.optional config.isoImage.makeEfiBootable "efivars";
 
-  # Need unionfs-fuse
-  boot.initrd.extraUtilsCommands = ''
-    cp -v ${pkgs.fuse}/lib/libfuse* $out/lib
-    cp -v ${pkgs.unionfs-fuse}/bin/unionfs $out/bin
-  '';
-
   # In stage 1, mount a tmpfs on top of / (the ISO image) and
   # /nix/store (the squashfs image) to make this a live CD.
   boot.initrd.postMountCommands =
     ''
-      # Hacky!!! fuse hard-codes the path to mount
-      mkdir -p /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
-      ln -s $(which mount) /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
-      ln -s $(which umount) /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
-
       mkdir -p /unionfs-chroot$targetRoot
       mount --rbind $targetRoot /unionfs-chroot$targetRoot
 
@@ -318,7 +307,7 @@ in
     '';
 
   # Add vfat support to the initrd to enable people to copy the
-  # contents of the CD to a bootable USB stick.
-  boot.initrd.supportedFilesystems = [ "vfat" ];
+  # contents of the CD to a bootable USB stick. Need unionfs-fuse for union mounts
+  boot.initrd.supportedFilesystems = [ "vfat" "unionfs-fuse" ];
     
 }

modules/module-list.nix

@@ -214,6 +214,7 @@
   ./tasks/filesystems/ext.nix
   ./tasks/filesystems/nfs.nix
   ./tasks/filesystems/reiserfs.nix
+  ./tasks/filesystems/unionfs-fuse.nix
   ./tasks/filesystems/vfat.nix
   ./tasks/filesystems/xfs.nix
   ./tasks/kbd.nix

modules/tasks/filesystems/unionfs-fuse.nix

@@ -0,0 +1,19 @@
+{ config, pkgs, ... }:
+
+{
+  config = pkgs.lib.mkIf (pkgs.lib.any (fs: fs == "unionfs-fuse") config.boot.initrd.supportedFilesystems) {
+    boot.initrd.kernelModules = [ "fuse" ];
+
+    boot.initrd.extraUtilsCommands = ''
+      cp -v ${pkgs.fuse}/lib/libfuse* $out/lib
+      cp -v ${pkgs.unionfs-fuse}/bin/unionfs $out/bin
+    '';
+
+    boot.initrd.postDeviceCommands = ''
+        # Hacky!!! fuse hard-codes the path to mount
+        mkdir -p /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
+        ln -s $(which mount) /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
+        ln -s $(which umount) /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
+      '';
+  };
+}

modules/virtualisation/qemu-vm.nix

@@ -252,16 +252,12 @@ in
   boot.initrd.availableKernelModules =
     [ "cifs" "nls_utf8" "hmac" "md4" "ecb" "des_generic" ];
 
-  # unionfs-fuse expects fuse to be loaded
-  boot.initrd.kernelModules = optional cfg.writableStore [ "fuse" ];
+  boot.initrd.supportedFilesystems = optional cfg.writableStore "unionfs-fuse";
 
   boot.initrd.extraUtilsCommands =
     ''
       # We need mke2fs in the initrd.
       cp ${pkgs.e2fsprogs}/sbin/mke2fs $out/bin
-    '' + optionalString cfg.writableStore ''
-      cp -v ${pkgs.fuse}/lib/libfuse* $out/lib
-      cp -v ${pkgs.unionfs-fuse}/bin/unionfs $out/bin
     '';
 
   boot.initrd.postDeviceCommands =
@@ -290,11 +286,6 @@ in
       mkdir -p $targetRoot/boot
       mount -o remount,ro $targetRoot/nix/store
       ${optionalString cfg.writableStore ''
-        # Hacky!!! fuse hard-codes the path to mount
-        mkdir -p /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
-        ln -s $(which mount) /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
-        ln -s $(which umount) /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-${pkgs.utillinux.name}/bin
-
         mkdir -p /unionfs-chroot$targetRoot
         mount --rbind $targetRoot /unionfs-chroot$targetRoot