* Fall back to the kernel modules used at boot time if the modules in

the current configuration don't match the running kernel.  This
  ensures that modprobe still works after a "nixos-rebuild switch" to
  a configuration that has a different kernel version.

svn path=/nixos/trunk/; revision=19696

modules/system/activation/top-level.nix

@@ -69,6 +69,7 @@ let
         false
       fi
       ln -s ${kernelPath} $out/kernel
+      ln -s ${config.system.modulesTree} $out/kernel-modules
       if [ -n "$grub" ]; then 
         ln -s $grub $out/grub
       fi

modules/system/boot/modprobe.nix

@@ -19,6 +19,14 @@ with pkgs.lib;
           ''
             #! ${pkgs.stdenv.shell}
             export MODULE_DIR=${config.system.modulesTree}/lib/modules
+            
+            # Fall back to the kernel modules used at boot time if the
+            # modules in the current configuration don't match the
+            # running kernel.
+            if [ ! -d "$MODULE_DIR/$(${pkgs.coreutils}/bin/uname -r)" ]; then
+                MODULE_DIR=/var/run/booted-system/kernel-modules/lib/modules
+            fi
+            
             exec ${pkgs.module_init_tools}/sbin/modprobe "$@"
           '';
       };