nixos/nix: use systemd-tmpfiles for inputs in $NIX_PATH

2 files changed, 19 insertions, 2 deletions

diff --git a/modules/nixos/defaults/nix.nix b/modules/nixos/defaults/nix.nix
index e55faf4..064b0d9 100644
--- a/modules/nixos/defaults/nix.nix
+++ b/modules/nixos/defaults/nix.nix
@@ -1,4 +1,4 @@
-{ lib, ... }:
+{ lib, inputs, ... }:
 {
   nix = {
     channel.enable = lib.mkDefault false;
@@ -9,4 +9,16 @@
   };
 
   nixpkgs.config.allowAliases = false;
+
+  # Link inputs for use in `$NIX_PATH`
+  systemd.tmpfiles.settings = {
+    nix-inputs = lib.mapAttrs' (
+      name: input:
+      lib.nameValuePair "/etc/nix/inputs/${name}" {
+        L = {
+          argument = input.outPath;
+        };
+      }
+    ) inputs;
+  };
 }
diff --git a/modules/shared/defaults/nix.nix b/modules/shared/defaults/nix.nix
index eb678a4..8ecdfe1 100644
--- a/modules/shared/defaults/nix.nix
+++ b/modules/shared/defaults/nix.nix
@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  inputs,
   ...
 }:
 let
@@ -13,6 +14,10 @@ let
     || lib.versionAtLeast config.nix.package.version "2.90.0"; # but not in lix yet
 
   hasAlwaysAllowSubstitutes = lib.versionAtLeast config.nix.package.version "2.19.0";
+
+  # Use systemd-tmpfiles on Linux
+  nixPathFromInput =
+    name: input: "${name}=${if isLinux then "/etc/nix/inputs/${name}" else input.outPath}";
 in
 {
   config = lib.mkMerge [
@@ -33,7 +38,7 @@ in
         };
 
         # See comment below
-        nixPath = [ "nixpkgs=${config.nixpkgs.flake.source}" ];
+        nixPath = lib.mapAttrsToList nixPathFromInput inputs;
       };
 
       nixpkgs = {