gpu: use tmpfiles.d to set up the /run/opengl-driver symlink

Signed-off-by: Esteve Fernandez <esteve@apache.org>

modules/targets/generic-linux/gpu/setup/default.nix

@@ -20,12 +20,12 @@ stdenv.mkDerivation {
     substituteInPlace non-nixos-gpu* \
       --replace-quiet '@@resources@@' "$out/resources" \
       --replace-quiet '@@statedir@@' '${nixStateDirectory}' \
-      --replace-quiet '@@systemddir@@' "$out/lib/systemd/system" \
+      --replace-quiet '@@tmpfilesdir@@' "$out/lib/tmpfiles.d" \
       --replace-quiet '@@env@@' "${nonNixosGpuEnv}"
   '';
   installPhase = ''
-    mkdir -p $out/{bin,resources,lib/systemd/system}
+    mkdir -p $out/{bin,resources,lib/tmpfiles.d}
     cp non-nixos-gpu-setup $out/bin
-    cp non-nixos-gpu.service $out/lib/systemd/system
+    cp non-nixos-gpu.conf $out/lib/tmpfiles.d
   '';
 }

modules/targets/generic-linux/gpu/setup/non-nixos-gpu-setup

@@ -2,12 +2,19 @@
 
 set -e
 
-# Install the systemd service file and ensure that the store path won't be
-# garbage-collected as long as it's installed.
-unit_path=/etc/systemd/system/non-nixos-gpu.service
-ln -sf @@systemddir@@/non-nixos-gpu.service "$unit_path"
-ln -sf "$unit_path" "@@statedir@@"/gcroots/non-nixos-gpu.service
+# Migrate from old systemd service setup
+old_unit=/etc/systemd/system/non-nixos-gpu.service
+if [[ -L "$old_unit" || -f "$old_unit" ]]; then
+  systemctl disable --now non-nixos-gpu.service 2>/dev/null || true
+  rm -f "$old_unit"
+  rm -f "@@statedir@@/gcroots/non-nixos-gpu.service"
+  systemctl daemon-reload
+fi
 
-systemctl daemon-reload
-systemctl enable non-nixos-gpu.service
-systemctl restart non-nixos-gpu.service
+# Install the tmpfiles.d config file and ensure that the store path won't be
+# garbage-collected as long as it's installed.
+conf_path=/etc/tmpfiles.d/non-nixos-gpu.conf
+ln -sf @@tmpfilesdir@@/non-nixos-gpu.conf "$conf_path"
+ln -sf "$conf_path" "@@statedir@@"/gcroots/non-nixos-gpu.conf
+
+systemd-tmpfiles --create non-nixos-gpu.conf

modules/targets/generic-linux/gpu/setup/non-nixos-gpu.conf

@@ -0,0 +1 @@
+L+ /run/opengl-driver - - - - @@env@@

modules/targets/generic-linux/gpu/setup/non-nixos-gpu.service

@@ -1,10 +0,0 @@
-[Unit]
-Description=GPU driver setup for Nix on non-NixOS Linux systems
-
-[Install]
-WantedBy=multi-user.target
-
-[Service]
-Type=oneshot
-ExecStart=ln -nsf @@env@@ /run/opengl-driver
-RemainAfterExit=yes