services: Use (guix build syscalls) instead of util-linux.

* gnu/services/dmd.scm (dmd-configuration-file): Add derivations for
  the (guix build syscalls) module, and add that to the load path of
  dmd.conf.
* gnu/services/base.scm (root-file-system-service): Rewrite using the
  'sync' and 'mount' procedures.

gnu/services/base.scm

@@ -22,8 +22,7 @@
   #:use-module (gnu system linux)                 ; 'pam-service', etc.
   #:use-module (gnu packages admin)
   #:use-module ((gnu packages base)
-                #:select (glibc-final %final-inputs))
+                #:select (glibc-final))
-  #:use-module (gnu packages linux)
   #:use-module (gnu packages package-management)
   #:use-module (guix gexp)
   #:use-module (guix monads)
@@ -52,9 +51,6 @@ system upon shutdown (aka. cleanly \"umounting\" root.)
 
 This service must be the root of the service dependency graph so that its
 'stop' action is invoked when dmd is the only process left."
-  (define coreutils
-    (car (assoc-ref %final-inputs "coreutils")))
-
   (with-monad %store-monad
     (return
      (service
@@ -63,7 +59,7 @@ This service must be the root of the service dependency graph so that its
       (start #~(const #t))
       (stop #~(lambda _
                 ;; Return #f if successfully stopped.
-                (system* (string-append #$coreutils "/bin/sync"))
+                (sync)
 
                 (call-with-blocked-asyncs
                  (lambda ()
@@ -82,12 +78,13 @@ This service must be the root of the service dependency graph so that its
                      ;; Close /dev/console.
                      (for-each close-fdes '(0 1 2))
 
-                     ;; At this points, there are no open files left, so the
+                     ;; At this point, there are no open files left, so the
                      ;; root file system can be re-mounted read-only.
-                     (not (zero?
+                     (mount #f "/" #f
-                           (system* (string-append #$util-linux "/bin/mount")
+                            (logior MS_REMOUNT MS_RDONLY)
-                                    "-n" "-o" "remount,ro"
+                            #:update-mtab? #f)
-                                    "-t" "dummy" "dummy" "/"))))))))
+
+                     #f)))))
       (respawn? #f)))))
 
 (define* (user-processes-service #:key (grace-delay 2))

gnu/services/dmd.scm

@@ -32,27 +32,39 @@
 
 (define (dmd-configuration-file services)
   "Return the dmd configuration file for SERVICES."
-  (define config
+  (define modules
-    #~(begin
+    ;; Extra modules visible to dmd.conf.
-        (use-modules (ice-9 ftw))
+    '((guix build syscalls)))
 
-        (register-services
+  (mlet %store-monad ((modules  (imported-modules modules))
-         #$@(map (lambda (service)
+                      (compiled (compiled-modules modules)))
-                   #~(make <service>
+    (define config
-                       #:docstring '#$(service-documentation service)
+      #~(begin
-                       #:provides '#$(service-provision service)
+          (eval-when (expand load eval)
-                       #:requires '#$(service-requirement service)
+            (set! %load-path (cons #$modules %load-path))
-                       #:respawn? '#$(service-respawn? service)
+            (set! %load-compiled-path
-                       #:start #$(service-start service)
+                  (cons #$compiled %load-compiled-path)))
-                       #:stop #$(service-stop service)))
-                 services))
 
-        ;; guix-daemon 0.6 aborts if 'PATH' is undefined, so work around it.
+          (use-modules (ice-9 ftw)
-        (setenv "PATH" "/run/current-system/bin")
+                       (guix build syscalls))
 
-        (format #t "starting services...~%")
+          (register-services
-        (for-each start '#$(append-map service-provision services))))
+           #$@(map (lambda (service)
+                     #~(make <service>
+                         #:docstring '#$(service-documentation service)
+                         #:provides '#$(service-provision service)
+                         #:requires '#$(service-requirement service)
+                         #:respawn? '#$(service-respawn? service)
+                         #:start #$(service-start service)
+                         #:stop #$(service-stop service)))
+                   services))
 
-  (gexp->file "dmd.conf" config))
+          ;; guix-daemon 0.6 aborts if 'PATH' is undefined, so work around it.
+          (setenv "PATH" "/run/current-system/bin")
+
+          (format #t "starting services...~%")
+          (for-each start '#$(append-map service-provision services))))
+
+    (gexp->file "dmd.conf" config)))
 
 ;;; dmd.scm ends here