1 files changed, 27 insertions, 0 deletions
diff --git a/nixos/modules/config/nix-channel.nix b/nixos/modules/config/nix-channel.nix
index 8e6061e4956..c37c3f73c30 100644
--- a/nixos/modules/config/nix-channel.nix
+++ b/nixos/modules/config/nix-channel.nix
@@ -12,6 +12,22 @@ let
 in
 {
   options = {
+    nix = {
+      nixPath = mkOption {
+        type = types.listOf types.str;
+        default = [
+          "nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos"
+          "nixos-config=/etc/nixos/configuration.nix"
+          "/nix/var/nix/profiles/per-user/root/channels"
+        ];
+        description = lib.mdDoc ''
+          The default Nix expression search path, used by the Nix
+          evaluator to look up paths enclosed in angle brackets
+          (e.g. `<nixpkgs>`).
+        '';
+      };
+    };
+
     system = {
       defaultChannel = mkOption {
         internal = true;
@@ -24,6 +40,17 @@ in
 
   config = mkIf cfg.enable {
 
+    environment.extraInit =
+      ''
+        if [ -e "$HOME/.nix-defexpr/channels" ]; then
+          export NIX_PATH="$HOME/.nix-defexpr/channels''${NIX_PATH:+:$NIX_PATH}"
+        fi
+      '';
+
+    environment.sessionVariables = {
+      NIX_PATH = cfg.nixPath;
+    };
+
     system.activationScripts.nix-channel = stringAfter [ "etc" "users" ]
       ''
         # Subscribe the root user to the NixOS channel by default.