systemd: Make "systemctl daemon-reexec" do the right thing on NixOS

pkgs/os-specific/linux/systemd/default.nix

@@ -13,7 +13,7 @@ stdenv.mkDerivation rec {
     sha256 = "1p3pf8gvx43g62l9x85l8ym12wc373cmaysi41sahjndp2agicig";
   };
 
-  patches = [ ./name_to_handle_at.patch ];
+  patches = [ ./name_to_handle_at.patch ./reexec.patch ];
 
   buildInputs =
     [ pkgconfig intltool gperf libcap dbus kmod xz pam acl

pkgs/os-specific/linux/systemd/reexec.patch

@@ -0,0 +1,15 @@
+Make "systemctl daemon-reexec" do the right thing on NixOS.
+
+diff --git a/src/core/main.c b/src/core/main.c
+index 04fc0b3..0f5b0e9 100644
+--- a/src/core/main.c
++++ b/src/core/main.c
+@@ -1819,7 +1819,7 @@ finish:
+                         char_array_0(sfd);
+ 
+                         i = 0;
+-                        args[i++] = SYSTEMD_BINARY_PATH;
++                        args[i++] = "/run/current-system/systemd/lib/systemd/systemd";
+                         if (switch_root_dir)
+                                 args[i++] = "--switched-root";
+                         args[i++] = arg_running_as == SYSTEMD_SYSTEM ? "--system" : "--user";