selinux fix

files/system/etc/selinux/targeted/contexts/files/file_contexts.local

@@ -0,0 +1,2 @@
+/nix(/.*)?                           system_u:object_r:bin_t:s0
+/var/lib/nix-store(/.*)?             system_u:object_r:bin_t:s0

files/system/etc/systemd/system/nix-daemon.service.d/selinux.conf

@@ -0,0 +1,5 @@
+[Service]
+# Run the daemon unconfined to avoid SELinux denials on the Nix store binaries.
+SELinuxContext=system_u:system_r:unconfined_service_t:s0
+ExecStart=
+ExecStart=/usr/bin/nix-daemon-wrapper.sh --daemon

files/system/usr/bin/mount-nix.sh

@@ -14,6 +14,13 @@ copy_seed_store() {
   fi
 }
 
+sync_missing_store() {
+  # Ensure any baked store paths exist in /var without clobbering user additions.
+  if command -v rsync >/dev/null 2>&1; then
+    rsync -aH --ignore-existing /usr/share/nix-store/store/ /var/lib/nix-store/store/
+  fi
+}
+
 ensure_system_profile() {
   local seed_profile="/usr/share/nix-store/var/nix/profiles/system"
   local target_profile="/var/lib/nix-store/var/nix/profiles/system"
@@ -21,7 +28,7 @@ ensure_system_profile() {
   mkdir -p /var/lib/nix-store/var/nix/profiles
 
   if { [ ! -e "$target_profile" ] || [ -L "$target_profile" ] && [ ! -e "$(readlink -f "$target_profile")" ]; } \
-     && [ -e "$seed_profile" ]; then
+     && { [ -e "$seed_profile" ] || [ -L "$seed_profile" ]; }; then
     cp -a "$seed_profile" "$target_profile"
   fi
 }
@@ -32,9 +39,14 @@ if ! mountpoint -q /nix; then
   fi
 
   ensure_system_profile
+  sync_missing_store
 
   mount --bind /var/lib/nix-store /nix
+  # Force an executable SELinux context on the bind mount so systemd can exec nix-daemon.
+  # Use a permissive fallback if the label option is rejected.
+  if ! mount -o remount,bind,exec,context=system_u:object_r:bin_t:s0 /nix 2>/dev/null; then
     mount -o remount,bind,exec /nix
+  fi
 
   # Ensure daemon paths exist and labels are sane.
   if command -v systemd-tmpfiles >/dev/null 2>&1; then

files/system/usr/bin/nix-daemon-wrapper.sh

@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+exec /nix/var/nix/profiles/system/bin/nix-daemon "$@"