1 files changed, 109 insertions, 0 deletions
diff --git a/nixpkgs/nixos/modules/profiles/clone-config.nix b/nixpkgs/nixos/modules/profiles/clone-config.nix
new file mode 100644
index 00000000000..3f669ba7d2e
--- /dev/null
+++ b/nixpkgs/nixos/modules/profiles/clone-config.nix
@@ -0,0 +1,109 @@
+{ config, lib, pkgs, modules, ... }:
+
+with lib;
+
+let
+
+  # Location of the repository on the harddrive
+  nixosPath = toString ../..;
+
+  # Check if the path is from the NixOS repository
+  isNixOSFile = path:
+    let s = toString path; in
+      removePrefix nixosPath s != s;
+
+  # Copy modules given as extra configuration files.  Unfortunately, we
+  # cannot serialized attribute set given in the list of modules (that's why
+  # you should use files).
+  moduleFiles =
+    # FIXME: use typeOf (Nix 1.6.1).
+    filter (x: !isAttrs x && !lib.isFunction x) modules;
+
+  # Partition module files because between NixOS and non-NixOS files.  NixOS
+  # files may change if the repository is updated.
+  partitionedModuleFiles =
+    let p = partition isNixOSFile moduleFiles; in
+    { nixos = p.right; others = p.wrong; };
+
+  # Path transformed to be valid on the installation device.  Thus the
+  # device configuration could be rebuild.
+  relocatedModuleFiles =
+    let
+      relocateNixOS = path:
+        "<nixpkgs/nixos" + removePrefix nixosPath (toString path) + ">";
+    in
+      { nixos = map relocateNixOS partitionedModuleFiles.nixos;
+        others = []; # TODO: copy the modules to the install-device repository.
+      };
+
+  # A dummy /etc/nixos/configuration.nix in the booted CD that
+  # rebuilds the CD's configuration (and allows the configuration to
+  # be modified, of course, providing a true live CD).  Problem is
+  # that we don't really know how the CD was built - the Nix
+  # expression language doesn't allow us to query the expression being
+  # evaluated.  So we'll just hope for the best.
+  configClone = pkgs.writeText "configuration.nix"
+    ''
+      { config, pkgs, ... }:
+
+      {
+        imports = [ ${toString config.installer.cloneConfigIncludes} ];
+
+        ${config.installer.cloneConfigExtra}
+      }
+    '';
+
+in
+
+{
+
+  options = {
+
+    installer.cloneConfig = mkOption {
+      default = true;
+      description = ''
+        Try to clone the installation-device configuration by re-using it's
+        profile from the list of imported modules.
+      '';
+    };
+
+    installer.cloneConfigIncludes = mkOption {
+      default = [];
+      example = [ "./nixos/modules/hardware/network/rt73.nix" ];
+      description = ''
+        List of modules used to re-build this installation device profile.
+      '';
+    };
+
+    installer.cloneConfigExtra = mkOption {
+      default = "";
+      description = ''
+        Extra text to include in the cloned configuration.nix included in this
+        installer.
+      '';
+    };
+  };
+
+  config = {
+
+    installer.cloneConfigIncludes =
+      relocatedModuleFiles.nixos ++ relocatedModuleFiles.others;
+
+    boot.postBootCommands =
+      ''
+        # Provide a mount point for nixos-install.
+        mkdir -p /mnt
+
+        ${optionalString config.installer.cloneConfig ''
+          # Provide a configuration for the CD/DVD itself, to allow users
+          # to run nixos-rebuild to change the configuration of the
+          # running system on the CD/DVD.
+          if ! [ -e /etc/nixos/configuration.nix ]; then
+            cp ${configClone} /etc/nixos/configuration.nix
+          fi
+       ''}
+      '';
+
+  };
+
+}