services: Rewrite using gexps.

* gnu/services.scm (<service>)[inputs]: Remove.
* gnu/system.scm (links): Remove.
  (etc-directory): Add PASSWD and SHADOW to #:inputs.
  (operating-system-boot-script): Pass ETC to 'dmd-configuration-file'.
  (operating-system-derivation): Remove EXTRAS from the union.
* gnu/system/linux.scm (pam-service->configuration): Rewrite in terms of
  'gexp->derivation'.  Compute the contents on the build side.  Expect
  'arguments' to contain a list of gexps.
  (pam-services->directory): Rewrite in terms of 'gexp->derivation'.
  (unix-pam-service): Change 'arguments' to a list of one gexp.
* gnu/system/shadow.scm (<user-account>)[inputs]: Remove.
  [shell]: Change default value to a gexp.
  (passwd-file): Rewrite in terms of 'gexp->derivation'.  Compute
  contents on the build side.
* gnu/services/base.scm (host-name-service, mingetty-service,
  nscd-service, syslog-service, guix-service): Change 'start' and 'stop'
  to gexps; remove 'inputs' field.
  (guix-build-accounts): Change 'shell' field to a gexp.
* gnu/services/networking.scm (static-networking-service): Change
  'start' and 'stop' to gexps; remove 'inputs' field.
* gnu/services/xorg.scm (slim-service): Likewise.
* gnu/services/dmd.scm (dmd-configuration-file): Expect ETC to be a
  derivation.  Change 'config' to a gexp.  Use 'gexp->file' instead of
  'text-file'.
* doc/guix.texi (Defining Services): Update nscd example with gexps, and
  without 'inputs'.  Add xref to "G-Expressions".

8 files changed, 173 insertions, 214 deletions

diff --git a/gnu/services.scm b/gnu/services.scm
index eccde4e9a3..8b89b11b8f 100644
--- a/gnu/services.scm
+++ b/gnu/services.scm
@@ -26,7 +26,6 @@
             service-respawn?
             service-start
             service-stop
-            service-inputs
             service-user-accounts
             service-user-groups
             service-pam-services))
@@ -47,11 +46,9 @@
                  (default '()))
   (respawn?      service-respawn?                 ; Boolean
                  (default #t))
-  (start         service-start)                   ; expression
-  (stop          service-stop                     ; expression
+  (start         service-start)                   ; g-expression
+  (stop          service-stop                     ; g-expression
                  (default #f))
-  (inputs        service-inputs                   ; list of inputs
-                 (default '()))
   (user-accounts service-user-accounts            ; list of <user-account>
                  (default '()))
   (user-groups   service-user-groups              ; list of <user-groups>
diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index 3145a657f8..9561995243 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -24,6 +24,7 @@
   #:use-module ((gnu packages base)
                 #:select (glibc-final))
   #:use-module (gnu packages package-management)
+  #:use-module (guix gexp)
   #:use-module (guix monads)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
@@ -48,8 +49,8 @@
     (return (service
              (documentation "Initialize the machine's host name.")
              (provision '(host-name))
-             (start `(lambda _
-                       (sethostname ,name)))
+             (start #~(lambda _
+                        (sethostname #$name)))
              (respawn? #f)))))
 
 (define* (mingetty-service tty
@@ -57,8 +58,7 @@
                            (motd (text-file "motd" "Welcome.\n"))
                            (allow-empty-passwords? #t))
   "Return a service to run mingetty on TTY."
-  (mlet %store-monad ((mingetty-bin (package-file mingetty "sbin/mingetty"))
-                      (motd         motd))
+  (mlet %store-monad ((motd motd))
     (return
      (service
       (documentation (string-append "Run mingetty on " tty "."))
@@ -68,10 +68,10 @@
       ;; service to be done.
       (requirement '(host-name))
 
-      (start  `(make-forkexec-constructor ,mingetty-bin "--noclear" ,tty))
-      (stop   `(make-kill-destructor))
-      (inputs `(("mingetty" ,mingetty)
-                ("motd" ,motd)))
+      (start  #~(make-forkexec-constructor
+                 (string-append #$mingetty "/sbin/mingetty")
+                 "--noclear" #$tty))
+      (stop   #~(make-kill-destructor))
 
       (pam-services
        ;; Let 'login' be known to PAM.  All the mingetty services will have
@@ -83,16 +83,17 @@
 
 (define* (nscd-service #:key (glibc glibc-final))
   "Return a service that runs libc's name service cache daemon (nscd)."
-  (mlet %store-monad ((nscd (package-file glibc "sbin/nscd")))
+  (with-monad %store-monad
     (return (service
              (documentation "Run libc's name service cache daemon (nscd).")
              (provision '(nscd))
-             (start `(make-forkexec-constructor ,nscd "-f" "/dev/null"
-                                                "--foreground"))
-             (stop  `(make-kill-destructor))
+             (start
+              #~(make-forkexec-constructor (string-append #$glibc "/sbin/nscd")
+                                           "-f" "/dev/null"
+                                           "--foreground"))
+             (stop #~(make-kill-destructor))
 
-             (respawn? #f)
-             (inputs `(("glibc" ,glibc)))))))
+             (respawn? #f)))))
 
 (define (syslog-service)
   "Return a service that runs 'syslogd' with reasonable default settings."
@@ -120,17 +121,17 @@
 ")
 
   (mlet %store-monad
-      ((syslog.conf (text-file "syslog.conf" contents))
-       (syslogd     (package-file inetutils "libexec/syslogd")))
+      ((syslog.conf (text-file "syslog.conf" contents)))
     (return
      (service
       (documentation "Run the syslog daemon (syslogd).")
       (provision '(syslogd))
-      (start `(make-forkexec-constructor ,syslogd "--no-detach"
-                                         "--rcfile" ,syslog.conf))
-      (stop  `(make-kill-destructor))
-      (inputs `(("inetutils" ,inetutils)
-                ("syslog.conf" ,syslog.conf)))))))
+      (start
+       #~(make-forkexec-constructor (string-append #$inetutils
+                                                   "/libexec/syslogd")
+                                    "--no-detach"
+                                    "--rcfile" #$syslog.conf))
+      (stop #~(make-kill-destructor))))))
 
 (define* (guix-build-accounts count #:key
                               (first-uid 30001)
@@ -148,8 +149,7 @@ starting at FIRST-UID, and under GID."
                        (gid gid)
                        (comment (format #f "Guix Build User ~2d" n))
                        (home-directory "/var/empty")
-                       (shell (package-file shadow "sbin/nologin"))
-                       (inputs `(("shadow" ,shadow)))))
+                       (shell #~(string-append #$shadow "/sbin/nologin"))))
                     1+
                     1))))
 
@@ -157,16 +157,16 @@ starting at FIRST-UID, and under GID."
                        (build-user-gid 30000) (build-accounts 10))
   "Return a service that runs the build daemon from GUIX, and has
 BUILD-ACCOUNTS user accounts available under BUILD-USER-GID."
-  (mlet %store-monad ((daemon   (package-file guix "bin/guix-daemon"))
-                      (accounts (guix-build-accounts build-accounts
+  (mlet %store-monad ((accounts (guix-build-accounts build-accounts
                                                      #:gid build-user-gid)))
     (return (service
              (provision '(guix-daemon))
-             (start `(make-forkexec-constructor ,daemon
-                                                "--build-users-group"
-                                                ,builder-group))
-             (stop  `(make-kill-destructor))
-             (inputs `(("guix" ,guix)))
+             (start
+              #~(make-forkexec-constructor (string-append #$guix
+                                                          "/bin/guix-daemon")
+                                           "--build-users-group"
+                                           #$builder-group))
+             (stop #~(make-kill-destructor))
              (user-accounts accounts)
              (user-groups (list (user-group
                                  (name builder-group)
diff --git a/gnu/services/dmd.scm b/gnu/services/dmd.scm
index 54fb5cbfd6..c187c09857 100644
--- a/gnu/services/dmd.scm
+++ b/gnu/services/dmd.scm
@@ -17,6 +17,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu services dmd)
+  #:use-module (guix gexp)
   #:use-module (guix monads)
   #:use-module (gnu services)
   #:use-module (ice-9 match)
@@ -31,50 +32,50 @@
 
 (define (dmd-configuration-file services etc)
   "Return the dmd configuration file for SERVICES, that initializes /etc from
-ETC (the name of a directory in the store) on startup."
+ETC (the derivation that builds the /etc directory) on startup."
   (define config
-    `(begin
-       (use-modules (ice-9 ftw))
+    #~(begin
+        (use-modules (ice-9 ftw))
 
-       (register-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))
+        (register-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))
 
-       ;; /etc is a mixture of static and dynamic settings.  Here is where we
-       ;; initialize it from the static part.
-       (format #t "populating /etc from ~a...~%" ,etc)
-       (let ((rm-f (lambda (f)
-                     (false-if-exception (delete-file f)))))
-         (rm-f "/etc/static")
-         (symlink ,etc "/etc/static")
-         (for-each (lambda (file)
-                     ;; TODO: Handle 'shadow' specially so that changed
-                     ;; password aren't lost.
-                     (let ((target (string-append "/etc/" file))
-                           (source (string-append "/etc/static/" file)))
-                       (rm-f target)
-                       (symlink source target)))
-                   (scandir ,etc
-                            (lambda (file)
-                              (not (member file '("." ".."))))))
+        ;; /etc is a mixture of static and dynamic settings.  Here is where we
+        ;; initialize it from the static part.
+        (format #t "populating /etc from ~a...~%" #$etc)
+        (let ((rm-f (lambda (f)
+                      (false-if-exception (delete-file f)))))
+          (rm-f "/etc/static")
+          (symlink #$etc "/etc/static")
+          (for-each (lambda (file)
+                      ;; TODO: Handle 'shadow' specially so that changed
+                      ;; password aren't lost.
+                      (let ((target (string-append "/etc/" file))
+                            (source (string-append "/etc/static/" file)))
+                        (rm-f target)
+                        (symlink source target)))
+                    (scandir #$etc
+                             (lambda (file)
+                               (not (member file '("." ".."))))))
 
-         ;; Prevent ETC from being GC'd.
-         (rm-f "/var/guix/gcroots/etc-directory")
-         (symlink ,etc "/var/guix/gcroots/etc-directory"))
+          ;; Prevent ETC from being GC'd.
+          (rm-f "/var/guix/gcroots/etc-directory")
+          (symlink #$etc "/var/guix/gcroots/etc-directory"))
 
-       ;; guix-daemon 0.6 aborts if 'PATH' is undefined, so work around it.
-       (setenv "PATH" "/run/current-system/bin")
+        ;; 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))))
+        (format #t "starting services...~%")
+        (for-each start '#$(append-map service-provision services))))
 
-  (text-file "dmd.conf" (object->string config)))
+  (gexp->file "dmd.conf" config))
 
 ;;; dmd.scm ends here
diff --git a/gnu/services/networking.scm b/gnu/services/networking.scm
index 317800db50..5522541735 100644
--- a/gnu/services/networking.scm
+++ b/gnu/services/networking.scm
@@ -20,6 +20,7 @@
   #:use-module (gnu services)
   #:use-module (gnu packages admin)
   #:use-module (gnu packages linux)
+  #:use-module (guix gexp)
   #:use-module (guix monads)
   #:export (static-networking-service))
 
@@ -41,40 +42,41 @@ true, it must be a string specifying the default network gateway."
   ;; TODO: Eventually we should do this using Guile's networking procedures,
   ;; like 'configure-qemu-networking' does, but the patch that does this is
   ;; not yet in stock Guile.
-  (mlet %store-monad ((ifconfig (package-file inetutils "bin/ifconfig"))
-                      (route    (package-file net-tools "sbin/route")))
+  (with-monad %store-monad
     (return
      (service
       (documentation
        (string-append "Set up networking on the '" interface
                       "' interface using a static IP address."))
       (provision '(networking))
-      (start `(lambda _
-                ;; Return #t if successfully started.
-                (and (zero? (system* ,ifconfig ,interface ,ip "up"))
-                     ,(if gateway
-                          `(zero? (system* ,route "add" "-net" "default"
-                                           "gw" ,gateway))
-                          #t)
-                     ,(if (pair? name-servers)
-                          `(call-with-output-file "/etc/resolv.conf"
-                             (lambda (port)
-                               (display
-                                "# Generated by 'static-networking-service'.\n"
-                                port)
-                               (for-each (lambda (server)
-                                           (format port "nameserver ~a~%"
-                                                   server))
-                                         ',name-servers)))
-                          #t))))
-      (stop  `(lambda _
+      (start #~(lambda _
+                 ;; Return #t if successfully started.
+                 (and (zero? (system* (string-append #$inetutils
+                                                     "/bin/ifconfig")
+                                      #$interface #$ip "up"))
+                      #$(if gateway
+                            #~(zero? (system* (string-append #$net-tools
+                                                             "/sbin/route")
+                                              "add" "-net" "default"
+                                              "gw" #$gateway))
+                            #t)
+                      #$(if (pair? name-servers)
+                            #~(call-with-output-file "/etc/resolv.conf"
+                                (lambda (port)
+                                  (display
+                                   "# Generated by 'static-networking-service'.\n"
+                                   port)
+                                  (for-each (lambda (server)
+                                              (format port "nameserver ~a~%"
+                                                      server))
+                                            '#$name-servers)))
+                            #t))))
+      (stop #~(lambda _
                 ;; Return #f is successfully stopped.
-                (not (and (system* ,ifconfig ,interface "down")
-                          (system* ,route "del" "-net" "default")))))
-      (respawn? #f)
-      (inputs `(("inetutils" ,inetutils)
-                ,@(if gateway
-                      `(("net-tools" ,net-tools))
-                      '())))))))
+                (not (and (system* (string-append #$inetutils "/sbin/ifconfig")
+                                   #$interface "down")
+                          (system* (string-append #$net-tools "/sbin/route")
+                                   "del" "-net" "default")))))
+      (respawn? #f)))))
 
 ;;; networking.scm ends here
diff --git a/gnu/services/xorg.scm b/gnu/services/xorg.scm
index 086150a658..81b5bc17a5 100644
--- a/gnu/services/xorg.scm
+++ b/gnu/services/xorg.scm
@@ -27,6 +27,7 @@
   #:use-module (gnu packages gnustep)
   #:use-module (gnu packages admin)
   #:use-module (gnu packages bash)
+  #:use-module (guix gexp)
   #:use-module (guix monads)
   #:use-module (guix derivations)
   #:export (xorg-start-command
@@ -190,9 +191,7 @@ reboot_cmd " dmd "/sbin/reboot
       (string-append "auto_login yes\ndefault_user " default-user)
       ""))))
 
-  (mlet %store-monad ((slim-bin (package-file slim "bin/slim"))
-                      (bash-bin (package-file bash "bin/bash"))
-                      (slim.cfg (slim.cfg)))
+  (mlet %store-monad ((slim.cfg (slim.cfg)))
     (return
      (service
       (documentation "Xorg display server")
@@ -200,15 +199,11 @@ reboot_cmd " dmd "/sbin/reboot
       (requirement '(host-name))
       (start
        ;; XXX: Work around the inability to specify env. vars. directly.
-       `(make-forkexec-constructor
-         ,bash-bin "-c"
-         ,(string-append "SLIM_CFGFILE=" (derivation->output-path slim.cfg)
-                         " " slim-bin
-                         " -nodaemon")))
-      (stop  `(make-kill-destructor))
-      (inputs `(("slim" ,slim)
-                ("slim.cfg" ,slim.cfg)
-                ("bash" ,bash)))
+       #~(make-forkexec-constructor
+          (string-append #$bash "/bin/sh") "-c"
+          (string-append "SLIM_CFGFILE=" #$slim.cfg
+                         " " #$slim "/bin/slim" " -nodaemon")))
+      (stop #~(make-kill-destructor))
       (respawn? #t)
       (pam-services
        ;; Tell PAM about 'slim'.
diff --git a/gnu/system.scm b/gnu/system.scm
index 65b524d387..20c49c182a 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -192,29 +192,6 @@ as an inputs; additional inputs, such as derivations, are taken from INPUTS."
                              #:inputs inputs
                              #:local-build? #t))))
 
-(define (links inputs)
-  "Return a directory with symbolic links to all of INPUTS.  This is
-essentially useful when one wants to keep references to all of INPUTS, be they
-directories or regular files."
-  (define builder
-    '(begin
-       (use-modules (srfi srfi-1))
-
-       (let ((out (assoc-ref %outputs "out")))
-         (mkdir out)
-         (chdir out)
-         (fold (lambda (file number)
-                 (symlink file (number->string number))
-                 (+ 1 number))
-               0
-               (map cdr %build-inputs))
-         #t)))
-
-  (mlet %store-monad ((inputs (lower-inputs inputs)))
-    (derivation-expression "links" builder
-                           #:inputs inputs
-                           #:local-build? #t)))
-
 (define* (etc-directory #:key
                         (locale "C") (timezone "Europe/Paris")
                         (accounts '())
@@ -272,12 +249,14 @@ alias ll='ls -l'
                    ("shells" ,shells)
                    ("profile" ,(derivation->output-path bashrc))
                    ("localtime" ,tz-file)
-                   ("passwd" ,passwd)
-                   ("shadow" ,shadow)
+                   ("passwd" ,(derivation->output-path passwd))
+                   ("shadow" ,(derivation->output-path shadow))
                    ("group" ,group))))
     (file-union files
                 #:inputs `(("net" ,net-base)
                            ("pam.d" ,pam.d)
+                           ("passwd" ,passwd)
+                           ("shadow" ,shadow)
                            ("bashrc" ,bashrc)
                            ("tzdata" ,tzdata))
                 #:name "etc")))
@@ -327,8 +306,7 @@ we're running in the final root."
   (mlet* %store-monad
       ((services (sequence %store-monad (operating-system-services os)))
        (etc      (operating-system-etc-directory os))
-       (dmd-conf (dmd-configuration-file services
-                                         (derivation->output-path etc))))
+       (dmd-conf (dmd-configuration-file services etc)))
     (gexp->file "boot"
                 #~(execl (string-append #$dmd "/bin/dmd")
                          "dmd" "--config" #$dmd-conf))))
@@ -357,25 +335,19 @@ we're running in the final root."
                            (linux-arguments `("--root=/dev/sda1"
                                               ,(string-append "--load=" boot)))
                            (initrd initrd-file))))
-       (grub.cfg (grub-configuration-file entries))
-       (accounts (operating-system-accounts os))
-       (extras   (links (delete-duplicates
-                         (append (append-map service-inputs services)
-                                 (append-map user-account-inputs accounts))))))
+       (grub.cfg (grub-configuration-file entries)))
     (file-union `(("boot" ,boot)
                   ("kernel" ,kernel-dir)
                   ("initrd" ,initrd-file)
                   ("profile" ,profile)
                   ("grub.cfg" ,grub.cfg)
-                  ("etc" ,etc)
-                  ("system-inputs" ,(derivation->output-path extras)))
+                  ("etc" ,etc))
                 #:inputs `(("boot" ,boot-drv)
                            ("kernel" ,kernel)
                            ("initrd" ,initrd)
                            ("bash" ,bash)
                            ("profile" ,profile-drv)
-                           ("etc" ,etc-drv)
-                           ("system-inputs" ,extras))
+                           ("etc" ,etc-drv))
                 #:name "system")))
 
 ;;; system.scm ends here
diff --git a/gnu/system/linux.scm b/gnu/system/linux.scm
index 65868ce9bf..efe27c55c3 100644
--- a/gnu/system/linux.scm
+++ b/gnu/system/linux.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -21,6 +21,7 @@
   #:use-module (guix records)
   #:use-module (guix derivations)
   #:use-module (guix monads)
+  #:use-module (guix gexp)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
@@ -58,58 +59,56 @@
 (define-record-type* <pam-entry> pam-entry
   make-pam-entry
   pam-entry?
-  (control    pam-entry-control)                  ; string
-  (module     pam-entry-module)                   ; file name
-  (arguments  pam-entry-arguments                 ; list of strings
+  (control    pam-entry-control)         ; string
+  (module     pam-entry-module)          ; file name
+  (arguments  pam-entry-arguments        ; list of string-valued g-expressions
               (default '())))
 
 (define (pam-service->configuration service)
-  "Return the configuration string for SERVICE, to be dumped in
-/etc/pam.d/NAME, where NAME is the name of SERVICE."
-  (define (entry->string type entry)
+  "Return the derivation building the configuration file for SERVICE, to be
+dumped in /etc/pam.d/NAME, where NAME is the name of SERVICE."
+  (define (entry->gexp type entry)
     (match entry
       (($ <pam-entry> control module (arguments ...))
-       (string-append type "  "
-                      control " " module " "
-                      (string-join arguments)
-                      "\n"))))
+       #~(format #t "~a ~a ~a ~a~%"
+                 #$type #$control #$module
+                 (string-join (list #$@arguments))))))
 
   (match service
     (($ <pam-service> name account auth password session)
-     (string-concatenate
-      (append (map (cut entry->string "account" <>) account)
-              (map (cut entry->string "auth" <>) auth)
-              (map (cut entry->string "password" <>) password)
-              (map (cut entry->string "session" <>) session))))))
+     (define builder
+       #~(begin
+           (with-output-to-file #$output
+             (lambda ()
+               #$@(append (map (cut entry->gexp "account" <>) account)
+                          (map (cut entry->gexp "auth" <>) auth)
+                          (map (cut entry->gexp "password" <>) password)
+                          (map (cut entry->gexp "session" <>) session))
+               #t))))
+
+     (gexp->derivation name builder))))
 
 (define (pam-services->directory services)
   "Return the derivation to build the configuration directory to be used as
 /etc/pam.d for SERVICES."
   (mlet %store-monad
       ((names -> (map pam-service-name services))
-       (files (mapm %store-monad
-                    (match-lambda
-                     ((and service ($ <pam-service> name))
-                      (let ((config (pam-service->configuration service)))
-                        (text-file (string-append name ".pam") config))))
-
-                    ;; XXX: Eventually, SERVICES may be a list of monadic
-                    ;; values instead of plain values.
-                    (map return services))))
+       (files (sequence %store-monad
+                        (map pam-service->configuration
+                             ;; XXX: Eventually, SERVICES may be a list of
+                             ;; monadic values instead of plain values.
+                             services))))
     (define builder
-      '(begin
-         (use-modules (ice-9 match))
+      #~(begin
+          (use-modules (ice-9 match))
 
-         (let ((out (assoc-ref %outputs "out")))
-           (mkdir out)
-           (for-each (match-lambda
-                      ((name . file)
-                       (symlink file (string-append out "/" name))))
-                     %build-inputs)
-           #t)))
+          (mkdir #$output)
+          (for-each (match-lambda
+                     ((name file)
+                      (symlink file (string-append #$output "/" name))))
+                    '#$(zip names files))))
 
-    (derivation-expression "pam.d" builder
-                           #:inputs (zip names files))))
+    (gexp->derivation "pam.d" builder)))
 
 (define %pam-other-services
   ;; The "other" PAM configuration, which denies everything (see
@@ -149,7 +148,8 @@ should be the name of a file used as the message-of-the-day."
                             (pam-entry
                              (control "optional")
                              (module "pam_motd.so")
-                             (arguments (list (string-append "motd=" motd)))))
+                             (arguments
+                              (list #~(string-append "motd=" #$motd)))))
                       (list unix))))))))
 
 ;;; linux.scm ends here
diff --git a/gnu/system/shadow.scm b/gnu/system/shadow.scm
index 2a85a20ebb..52242ee4e0 100644
--- a/gnu/system/shadow.scm
+++ b/gnu/system/shadow.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -20,6 +20,7 @@
   #:use-module (guix store)
   #:use-module (guix records)
   #:use-module (guix packages)
+  #:use-module (guix gexp)
   #:use-module (guix monads)
   #:use-module ((gnu packages admin)
                 #:select (shadow))
@@ -35,7 +36,6 @@
             user-account-comment
             user-account-home-directory
             user-account-shell
-            user-account-inputs
 
             user-group
             user-group?
@@ -63,9 +63,8 @@
   (gid            user-account-gid)
   (comment        user-account-comment (default ""))
   (home-directory user-account-home-directory)
-  (shell          user-account-shell              ; monadic value
-                  (default (package-file bash "bin/bash")))
-  (inputs         user-account-inputs (default `(("bash" ,bash)))))
+  (shell          user-account-shell              ; gexp
+                  (default #~(string-append #$bash "/bin/bash"))))
 
 (define-record-type* <user-group>
   user-group make-user-group
@@ -97,29 +96,22 @@
 SHADOW? is true, then it is a /etc/shadow file, otherwise it is a /etc/passwd
 file."
   ;; XXX: The resulting file is world-readable, so beware when SHADOW? is #t!
-  (define (contents)
-    (with-monad %store-monad
-      (let loop ((accounts accounts)
-                 (result   '()))
-        (match accounts
-          ((($ <user-account> name pass uid gid comment home-dir mshell)
-            rest ...)
-           (mlet %store-monad ((shell mshell))
-             (loop rest
-                   (cons (if shadow?
-                             (string-append name
-                                            ":"    ; XXX: use (crypt PASS …)?
-                                            ":::::::")
-                             (string-append name
-                                            ":" "x"
-                                            ":" (number->string uid)
-                                            ":" (number->string gid)
-                                            ":" comment ":" home-dir ":" shell))
-                         result))))
-          (()
-           (return (string-join (reverse result) "\n" 'suffix)))))))
+  (define account-exp
+    (match-lambda
+     (($ <user-account> name pass uid gid comment home-dir shell)
+      (if shadow?                                 ; XXX: use (crypt PASS …)?
+          #~(format #t "~a::::::::~%" #$name)
+          #~(format #t "~a:x:~a:~a:~a:~a:~a~%"
+                    #$name #$(number->string uid) #$(number->string gid)
+                    #$comment #$home-dir #$shell)))))
 
-  (mlet %store-monad ((contents (contents)))
-    (text-file (if shadow? "shadow" "passwd") contents)))
+  (define builder
+    #~(begin
+        (with-output-to-file #$output
+          (lambda ()
+            #$@(map account-exp accounts)
+            #t))))
+
+  (gexp->derivation (if shadow? "shadow" "passwd") builder))
 
 ;;; shadow.scm ends here