From 2b2b69cc17df9ea22c9e9c36b2655c854068855c Mon Sep 17 00:00:00 2001
From: winston <hey@winston.sh>
Date: Mon, 25 May 2026 12:30:39 +0200
Subject: [PATCH] nixos/gdm: ensure environment from display-manager.service is
 propagated

---
 nixos/modules/services/display-managers/gdm.nix | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/nixos/modules/services/display-managers/gdm.nix b/nixos/modules/services/display-managers/gdm.nix
index dd043cbf272a..b10c60436919 100644
--- a/nixos/modules/services/display-managers/gdm.nix
+++ b/nixos/modules/services/display-managers/gdm.nix
@@ -455,6 +455,22 @@ in
               settings.conffile = "/etc/pam/environment";
               settings.readenv = 0;
             }
+            # make sure the spawned session has the same variables as `display-manager.service`
+            # https://github.com/NixOS/nixpkgs/issues/523332
+            {
+              name = "env-greeter";
+              control = "required";
+              modulePath = "${config.security.pam.package}/lib/security/pam_env.so";
+              settings.conffile =
+                let
+                  env = config.services.displayManager.generic.environment;
+                in
+                pkgs.writeText "gdm-launch-environment-env-conf" ''
+                  PATH          DEFAULT="''${PATH}:${pkgs.gnome-session}/bin"
+                  XDG_DATA_DIRS DEFAULT="''${XDG_DATA_DIRS}:${env.XDG_DATA_DIRS}"
+                '';
+              settings.readenv = 0;
+            }
             {
               name = "systemd";
               control = "optional";