From dfca7cafbbe14c4d6ccf142eb80d55e2f7cccc5c Mon Sep 17 00:00:00 2001
From: Artemis Tosini <artemis.tosini@obsidian.systems>
Date: Tue, 4 Aug 2026 10:47:17 -0400
Subject: [PATCH] nixos/nix-daemon: Set HOME for unprivileged daemon

Fixes issues with fetching from substituter while running with an
unprivileged daemon.

Using the StateDirectory instead of CacheDirectory here since it is
unclear what Nix will store there in the future.
---
 nixos/modules/services/system/nix-daemon.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/nixos/modules/services/system/nix-daemon.nix b/nixos/modules/services/system/nix-daemon.nix
index 97a5752bd35c..ab799c778a34 100644
--- a/nixos/modules/services/system/nix-daemon.nix
+++ b/nixos/modules/services/system/nix-daemon.nix
@@ -102,10 +102,14 @@ in
         systemd.services.nix-daemon = {
           # Nix assumes it should use `daemon` if it isn't root, so we have to set `NIX_REMOTE` anyway
           environment.NIX_REMOTE = "local?use-roots-daemon=true";
+          # Nix wants a HOME it can access to cache substituter contents, among other things.
+          environment.HOME = "%S/nix-daemon";
           serviceConfig = {
             User = cfg.daemonUser;
             Group = cfg.daemonGroup;
 
+            StateDirectory = "nix-daemon";
+
             # Empty string needed to disable old Exec
             ExecStart = [
               ""