guix/gnu/services/base.scm

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013-2022 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015, 2016 Alex Kost <alezost@gmail.com>
;;; Copyright © 2015, 2016, 2020 Mark H Weaver <mhw@netris.org>
;;; Copyright © 2015 Sou Bunnbu <iyzsong@gmail.com>
;;; Copyright © 2016, 2017 Leo Famulari <leo@famulari.name>
;;; Copyright © 2016 David Craven <david@craven.ch>
;;; Copyright © 2016 Ricardo Wurmus <rekado@elephly.net>
;;; Copyright © 2018 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2019 Efraim Flashner <efraim@flashner.co.il>
;;; Copyright © 2019 Tobias Geerinckx-Rice <me@tobias.gr>
;;; Copyright © 2019 John Soo <jsoo1@asu.edu>
;;; Copyright © 2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
;;; Copyright © 2020 Florian Pelz <pelzflorian@pelzflorian.de>
;;; Copyright © 2020, 2021 Brice Waegeneire <brice@waegenei.re>
;;; Copyright © 2021 qblade <qblade@protonmail.com>
;;; Copyright © 2021 Hui Lu <luhuins@163.com>
;;; Copyright © 2021, 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
;;; Copyright © 2022 Guillaume Le Vaillant <glv@posteo.net>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu services base)
  #:use-module (guix store)
  #:use-module (guix deprecation)
  #:autoload   (guix diagnostics) (warning &fix-hint)
  #:autoload   (guix i18n) (G_)
  #:use-module (guix combinators)
  #:use-module (gnu services)
  #:use-module (gnu services admin)
  #:use-module (gnu services shepherd)
  #:use-module (gnu services sysctl)
  #:use-module (gnu system pam)
  #:use-module (gnu system shadow)                ; 'user-account', etc.
  #:use-module (gnu system uuid)
  #:use-module (gnu system file-systems)          ; 'file-system', etc.
  #:use-module (gnu system keyboard)
  #:use-module (gnu system mapped-devices)
  #:use-module ((gnu system linux-initrd)
                #:select (file-system-packages))
  #:use-module (gnu packages admin)
  #:use-module ((gnu packages linux)
                #:select (alsa-utils crda eudev e2fsprogs fuse gpm kbd lvm2 rng-tools))
  #:use-module (gnu packages bash)
  #:use-module ((gnu packages base)
                #:select (coreutils glibc glibc-utf8-locales tar))
  #:use-module ((gnu packages compression) #:select (gzip))
  #:autoload   (gnu packages guile-xyz) (guile-netlink)
  #:autoload   (gnu packages hurd) (hurd)
  #:use-module (gnu packages package-management)
  #:use-module ((gnu packages gnupg) #:select (guile-gcrypt))
  #:use-module (gnu packages linux)
  #:use-module (gnu packages terminals)
  #:use-module ((gnu build file-systems)
                #:select (mount-flags->bit-mask
                          swap-space->flags-bit-mask))
  #:use-module (guix gexp)
  #:use-module (guix records)
  #:use-module (guix modules)
  #:use-module ((guix self) #:select (make-config.scm))
  #:use-module (guix diagnostics)
  #:use-module (guix i18n)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:use-module (ice-9 match)
  #:use-module (ice-9 format)
  #:re-export (user-processes-service-type        ;backwards compatibility
               %default-substitute-urls)
  #:export (fstab-service-type
            root-file-system-service
            file-system-service-type
            swap-service
            host-name-service
            %default-console-font
            console-font-service-type
            console-font-service
            virtual-terminal-service-type

            static-networking
            static-networking?
            static-networking-addresses
            static-networking-links
            static-networking-routes
            static-networking-requirement

            network-address
            network-address?
            network-address-device
            network-address-value
            network-address-ipv6?

            network-link
            network-link?
            network-link-name
            network-link-type
            network-link-arguments

            network-route
            network-route?
            network-route-destination
            network-route-source
            network-route-device
            network-route-ipv6?
            network-route-gateway

            static-networking-service
            static-networking-service-type

            %loopback-static-networking
            %qemu-static-networking

            udev-configuration
            udev-configuration?
            udev-configuration-rules
            udev-service-type
            udev-service
            udev-rule
            file->udev-rule
            udev-rules-service

            login-configuration
            login-configuration?
            login-service-type
            login-service

            agetty-configuration
            agetty-configuration?
            agetty-service
            agetty-service-type

            mingetty-configuration
            mingetty-configuration-tty
            mingetty-configuration-auto-login
            mingetty-configuration-login-program
            mingetty-configuration-login-pause?
            mingetty-configuration-clear-on-logout?
            mingetty-configuration-mingetty
            mingetty-configuration?
            mingetty-service
            mingetty-service-type

            %nscd-default-caches
            %nscd-default-configuration

            nscd-configuration
            nscd-configuration?

            nscd-cache
            nscd-cache?

            nscd-service-type
            nscd-service

            syslog-configuration
            syslog-configuration?
            syslog-service
            syslog-service-type
            %default-syslog.conf

            %default-authorized-guix-keys
            guix-configuration
            guix-configuration?

            guix-configuration-guix
            guix-configuration-build-group
            guix-configuration-build-accounts
            guix-configuration-authorize-key?
            guix-configuration-authorized-keys
            guix-configuration-use-substitutes?
            guix-configuration-substitute-urls
            guix-configuration-extra-options
            guix-configuration-log-file

            guix-service-type
            guix-publish-configuration
            guix-publish-configuration?
            guix-publish-configuration-guix
            guix-publish-configuration-port
            guix-publish-configuration-host
            guix-publish-configuration-compression
            guix-publish-configuration-compression-level ;deprecated
            guix-publish-configuration-nar-path
            guix-publish-configuration-cache
            guix-publish-configuration-ttl
            guix-publish-configuration-negative-ttl
            guix-publish-service-type

            gpm-configuration
            gpm-configuration?
            gpm-service-type

            urandom-seed-service-type

            rngd-configuration
            rngd-configuration?
            rngd-service-type
            rngd-service

            kmscon-configuration
            kmscon-configuration?
            kmscon-service-type

            pam-limits-service-type
            pam-limits-service

            references-file

            %base-services))

;;; Commentary:
;;;
;;; Base system services---i.e., services that 99% of the users will want to
;;; use.
;;;
;;; Code:



;;;
;;; File systems.
;;;

(define (file-system->fstab-entry file-system)
  "Return a @file{/etc/fstab} entry for @var{file-system}."
  (string-append (match (file-system-device file-system)
                   ((? file-system-label? label)
                    (string-append "LABEL="
                                   (file-system-label->string label)))
                   ((? uuid? uuid)
                    (string-append "UUID=" (uuid->string uuid)))
                   ((? string? device)
                    device))
                 "\t"
                 (file-system-mount-point file-system) "\t"
                 (file-system-type file-system) "\t"
                 (or (file-system-options file-system) "defaults") "\t"

                 ;; XXX: Omit the 'fs_freq' and 'fs_passno' fields because we
                 ;; don't have anything sensible to put in there.
                 ))

(define (file-systems->fstab file-systems)
  "Return a @file{/etc} entry for an @file{fstab} describing
@var{file-systems}."
  `(("fstab" ,(plain-file "fstab"
                          (string-append
                           "\
# This file was generated from your Guix configuration.  Any changes
# will be lost upon reboot or reconfiguration.\n\n"
                           (string-join (map file-system->fstab-entry
                                             file-systems)
                                        "\n")
                           "\n")))))

(define fstab-service-type
  ;; The /etc/fstab service.
  (service-type (name 'fstab)
                (extensions
                 (list (service-extension etc-service-type
                                          file-systems->fstab)))
                (compose concatenate)
                (extend append)
                (description
                 "Populate the @file{/etc/fstab} based on the given file
system objects.")))

(define %root-file-system-shepherd-service
  (shepherd-service
   (documentation "Take care of the root file system.")
   (provision '(root-file-system))
   (start #~(const #t))
   (stop #~(lambda _
             ;; Return #f if successfully stopped.
             (sync)

             (call-with-blocked-asyncs
              (lambda ()
                (let ((null (%make-void-port "w")))
                  ;; Close 'shepherd.log'.
                  (display "closing log\n")
                  ((@ (shepherd comm) stop-logging))

                  ;; Redirect the default output ports..
                  (set-current-output-port null)
                  (set-current-error-port null)

                  ;; Close /dev/console.
                  (for-each close-fdes '(0 1 2))

                  ;; At this point, there are no open files left, so the
                  ;; root file system can be re-mounted read-only.
                  (mount #f "/" #f
                         (logior MS_REMOUNT MS_RDONLY)
                         #:update-mtab? #f)

                  #f)))))
   (respawn? #f)))

(define root-file-system-service-type
  (shepherd-service-type 'root-file-system
                         (const %root-file-system-shepherd-service)
                         (description "Take care of syncing the root file
system and of remounting it read-only when the system shuts down.")))

(define (root-file-system-service)
  "Return a service whose sole purpose is to re-mount read-only the root file
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 shepherd is the only process left."
  (service root-file-system-service-type #f))

(define (file-system->shepherd-service-name file-system)
  "Return the symbol that denotes the service mounting and unmounting
FILE-SYSTEM."
  (symbol-append 'file-system-
                 (string->symbol (file-system-mount-point file-system))))

(define (mapped-device->shepherd-service-name md)
  "Return the symbol that denotes the shepherd service of MD, a <mapped-device>."
  (symbol-append 'device-mapping-
                 (string->symbol (string-join
                                  (mapped-device-targets md) "-"))))

(define dependency->shepherd-service-name
  (match-lambda
    ((? mapped-device? md)
     (mapped-device->shepherd-service-name md))
    ((? file-system? fs)
     (file-system->shepherd-service-name fs))))

(define (file-system-shepherd-service file-system)
  "Return the shepherd service for @var{file-system}, or @code{#f} if
@var{file-system} is not auto-mounted or doesn't have its mount point created
upon boot."
  (let ((target  (file-system-mount-point file-system))
        (create? (file-system-create-mount-point? file-system))
        (mount?  (file-system-mount? file-system))
        (dependencies (file-system-dependencies file-system))
        (packages (file-system-packages (list file-system))))
    (and (or mount? create?)
         (with-imported-modules (source-module-closure
                                 '((gnu build file-systems)))
           (shepherd-service
            (provision (list (file-system->shepherd-service-name file-system)))
            (requirement `(root-file-system
                           udev
                           ,@(map dependency->shepherd-service-name dependencies)))
            (documentation "Check, mount, and unmount the given file system.")
            (start #~(lambda args
                       #$(if create?
                             #~(mkdir-p #$target)
                             #t)

                       #$(if mount?
                             #~(let (($PATH (getenv "PATH")))
                                 ;; Make sure fsck.ext2 & co. can be found.
                                 (dynamic-wind
                                   (lambda ()
                                     ;; Don’t display the PATH settings.
                                     (with-output-to-port (%make-void-port "w")
                                       (lambda ()
                                         (set-path-environment-variable "PATH"
                                                                        '("bin" "sbin")
                                                                        '#$packages))))
                                   (lambda ()
                                     (mount-file-system
                                      (spec->file-system
                                       '#$(file-system->spec file-system))
                                      #:root "/"))
                                   (lambda ()
                                     (setenv "PATH" $PATH))))
                             #t)
                       #t))
            (stop #~(lambda args
                      ;; Normally there are no processes left at this point, so
                      ;; TARGET can be safely unmounted.

                      ;; Make sure PID 1 doesn't keep TARGET busy.
                      (chdir "/")

                      (umount #$target)
                      #f))

            ;; We need additional modules.
            (modules `(((gnu build file-systems)
                        #:select (mount-file-system))
                       (gnu system file-systems)
                       ,@%default-modules)))))))

(define (file-system-shepherd-services file-systems)
  "Return the list of Shepherd services for FILE-SYSTEMS."
  (let* ((file-systems (filter (lambda (x)
                                 (or (file-system-mount? x)
                                     (file-system-create-mount-point? x)))
                               file-systems)))
    (define sink
      (shepherd-service
       (provision '(file-systems))
       (requirement (cons* 'root-file-system 'user-file-systems
                           (map file-system->shepherd-service-name
                                file-systems)))
       (documentation "Target for all the initially-mounted file systems")
       (start #~(const #t))
       (stop #~(const #f))))

    (define known-mount-points
      (map file-system-mount-point file-systems))

    (define user-unmount
      (shepherd-service
       (documentation "Unmount manually-mounted file systems.")
       (provision '(user-file-systems))
       (start #~(const #t))
       (stop #~(lambda args
                 (define (known? mount-point)
                   (member mount-point
                           (cons* "/proc" "/sys" '#$known-mount-points)))

                 ;; Make sure we don't keep the user's mount points busy.
                 (chdir "/")

                 (for-each (lambda (mount-point)
                             (format #t "unmounting '~a'...~%" mount-point)
                             (catch 'system-error
                               (lambda ()
                                 (umount mount-point))
                               (lambda args
                                 (let ((errno (system-error-errno args)))
                                   (format #t "failed to unmount '~a': ~a~%"
                                           mount-point (strerror errno))))))
                           (filter (negate known?) (mount-points)))
                 #f))))

    (cons* sink user-unmount
           (map file-system-shepherd-service file-systems))))

(define (file-system-fstab-entries file-systems)
  "Return the subset of @var{file-systems} that should have an entry in
@file{/etc/fstab}."
  ;; /etc/fstab is about telling fsck(8), mount(8), and umount(8) about
  ;; relevant file systems they'll have to deal with.  That excludes "pseudo"
  ;; file systems.
  ;;
  ;; In particular, things like GIO (part of GLib) use it to determine the set
  ;; of mounts, which is then used by graphical file managers and desktop
  ;; environments to display "volume" icons.  Thus, we really need to exclude
  ;; those pseudo file systems from the list.
  (remove (lambda (file-system)
            (or (member (file-system-type file-system)
                        %pseudo-file-system-types)
                (memq 'bind-mount (file-system-flags file-system))))
          file-systems))

(define file-system-service-type
  (service-type (name 'file-systems)
                (extensions
                 (list (service-extension shepherd-root-service-type
                                          file-system-shepherd-services)
                       (service-extension fstab-service-type
                                          file-system-fstab-entries)

                       ;; Have 'user-processes' depend on 'file-systems'.
                       (service-extension user-processes-service-type
                                          (const '(file-systems)))))
                (compose concatenate)
                (extend append)
                (description
                 "Provide Shepherd services to mount and unmount the given
file systems, as well as corresponding @file{/etc/fstab} entries.")))



;;;
;;; Preserve entropy to seed /dev/urandom on boot.
;;;

(define %random-seed-file
  "/var/lib/random-seed")

(define (urandom-seed-shepherd-service _)
  "Return a shepherd service for the /dev/urandom seed."
  (list (shepherd-service
         (documentation "Preserve entropy across reboots for /dev/urandom.")
         (provision '(urandom-seed))

         ;; Depend on udev so that /dev/hwrng is available.
         (requirement '(file-systems udev))

         (start #~(lambda _
                    ;; On boot, write random seed into /dev/urandom.
                    (when (file-exists? #$%random-seed-file)
                      (call-with-input-file #$%random-seed-file
                        (lambda (seed)
                          (call-with-output-file "/dev/urandom"
                            (lambda (urandom)
                              (dump-port seed urandom)

                              ;; Writing SEED to URANDOM isn't enough: we must
                              ;; also tell the kernel to account for these
                              ;; extra bits of entropy.
                              (let ((bits (* 8 (stat:size (stat seed)))))
                                (add-to-entropy-count urandom bits)))))))

                    ;; Try writing from /dev/hwrng into /dev/urandom.
                    ;; It seems that the file /dev/hwrng always exists, even
                    ;; when there is no hardware random number generator
                    ;; available. So, we handle a failed read or any other error
                    ;; reported by the operating system.
                    (let ((buf (catch 'system-error
                                 (lambda ()
                                   (call-with-input-file "/dev/hwrng"
                                     (lambda (hwrng)
                                       (get-bytevector-n hwrng 512))))
                                 ;; Silence is golden...
                                 (const #f))))
                      (when buf
                        (call-with-output-file "/dev/urandom"
                          (lambda (urandom)
                            (put-bytevector urandom buf)
                            (let ((bits (* 8 (bytevector-length buf))))
                              (add-to-entropy-count urandom bits))))))

                    ;; Immediately refresh the seed in case the system doesn't
                    ;; shut down cleanly.
                    (call-with-input-file "/dev/urandom"
                      (lambda (urandom)
                        (let ((previous-umask (umask #o077))
                              (buf (make-bytevector 512)))
                          (mkdir-p (dirname #$%random-seed-file))
                          (get-bytevector-n! urandom buf 0 512)
                          (call-with-output-file #$%random-seed-file
                            (lambda (seed)
                              (put-bytevector seed buf)))
                          (umask previous-umask))))
                    #t))
         (stop #~(lambda _
                   ;; During shutdown, write from /dev/urandom into random seed.
                   (let ((buf (make-bytevector 512)))
                     (call-with-input-file "/dev/urandom"
                       (lambda (urandom)
                         (let ((previous-umask (umask #o077)))
                           (get-bytevector-n! urandom buf 0 512)
                           (mkdir-p (dirname #$%random-seed-file))
                           (call-with-output-file #$%random-seed-file
                             (lambda (seed)
                               (put-bytevector seed buf)))
                           (umask previous-umask))
                         #t)))))
         (modules `((rnrs bytevectors)
                    (rnrs io ports)
                    ,@%default-modules)))))

(define urandom-seed-service-type
  (service-type (name 'urandom-seed)
                (extensions
                 (list (service-extension shepherd-root-service-type
                                          urandom-seed-shepherd-service)

                       ;; Have 'user-processes' depend on 'urandom-seed'.
                       ;; This ensures that user processes and daemons don't
                       ;; start until we have seeded the PRNG.
                       (service-extension user-processes-service-type
                                          (const '(urandom-seed)))))
                (default-value #f)
                (description
                 "Seed the @file{/dev/urandom} pseudo-random number
generator (RNG) with the value recorded when the system was last shut
down.")))


;;;
;;; Add hardware random number generator to entropy pool.
;;;

(define-record-type* <rngd-configuration>
  rngd-configuration make-rngd-configuration
  rngd-configuration?
  (rng-tools rngd-configuration-rng-tools)        ;file-like
  (device    rngd-configuration-device))          ;string

(define rngd-service-type
  (shepherd-service-type
    'rngd
    (lambda (config)
      (define rng-tools (rngd-configuration-rng-tools config))
      (define device (rngd-configuration-device config))

      (define rngd-command
        (list (file-append rng-tools "/sbin/rngd")
              "-f" "-r" device))

      (shepherd-service
        (documentation "Add TRNG to entropy pool.")
        (requirement '(udev))
        (provision '(trng))
        (start #~(make-forkexec-constructor '#$rngd-command))
        (stop #~(make-kill-destructor))))
    (description "Run the @command{rngd} random number generation daemon to
supply entropy to the kernel's pool.")))

(define* (rngd-service #:key
                       (rng-tools rng-tools)
                       (device "/dev/hwrng"))
  "Return a service that runs the @command{rngd} program from @var{rng-tools}
to add @var{device} to the kernel's entropy pool.  The service will fail if
@var{device} does not exist."
  (service rngd-service-type
           (rngd-configuration
            (rng-tools rng-tools)
            (device device))))


;;;
;;; Console & co.
;;;

(define host-name-service-type
  (shepherd-service-type
   'host-name
   (lambda (name)
     (shepherd-service
      (documentation "Initialize the machine's host name.")
      (provision '(host-name))
      (start #~(lambda _
                 (sethostname #$name)))
      (one-shot? #t)))
   (description "Initialize the machine's host name.")))

(define (host-name-service name)
  "Return a service that sets the host name to @var{name}."
  (service host-name-service-type name))

(define virtual-terminal-service-type
  ;; Ensure that virtual terminals run in UTF-8 mode.  This is the case by
  ;; default with recent Linux kernels, but this service allows us to ensure
  ;; this.  This service must start before any 'term-' service so that newly
  ;; created terminals inherit this property.  See
  ;; <https://bugs.gnu.org/30505> for a discussion.
  (shepherd-service-type
   'virtual-terminal
   (lambda (utf8?)
     (let ((knob "/sys/module/vt/parameters/default_utf8"))
       (shepherd-service
        (documentation "Set virtual terminals in UTF-8 module.")
        (provision '(virtual-terminal))
        (requirement '(root-file-system))
        (start #~(lambda _
                   ;; In containers /sys is read-only so don't insist on
                   ;; writing to this file.
                   (unless (= 1 (call-with-input-file #$knob read))
                     (call-with-output-file #$knob
                       (lambda (port)
                         (display 1 port))))
                   #t))
        (stop #~(const #f)))))
   #t                                             ;default to UTF-8
   (description "Ensure the Linux virtual terminals run in UTF-8 mode.")))

(define console-keymap-service-type
  (shepherd-service-type
   'console-keymap
   (lambda (files)
     (shepherd-service
      (documentation (string-append "Load console keymap (loadkeys)."))
      (provision '(console-keymap))
      (start #~(lambda _
                 (zero? (system* #$(file-append kbd "/bin/loadkeys")
                                 #$@files))))
      (respawn? #f)))
   (description "@emph{This service is deprecated in favor of the
@code{keyboard-layout} field of @code{operating-system}.}  Load the given list
of console keymaps with @command{loadkeys}.")))

(define %default-console-font
  ;; Note: 'LatGrkCyr-8x16' has the advantage of providing three common
  ;; scripts as well as glyphs for em dash, quotation marks, and other Unicode
  ;; codepoints notably found in the UTF-8 manual.
  "LatGrkCyr-8x16")

(define (console-font-shepherd-services tty+font)
  "Return a list of Shepherd services for each pair in TTY+FONT."
  (map (match-lambda
         ((tty . font)
          (let ((device (string-append "/dev/" tty)))
            (shepherd-service
             (documentation "Load a Unicode console font.")
             (provision (list (symbol-append 'console-font-
                                             (string->symbol tty))))

             ;; Start after mingetty has been started on TTY, otherwise the settings
             ;; are ignored.
             (requirement (list (symbol-append 'term-
                                               (string->symbol tty))))

             (start #~(lambda _
                        ;; It could be that mingetty is not fully ready yet,
                        ;; which we check by calling 'ttyname'.
                        (let loop ((i 10))
                          (unless (or (zero? i)
                                      (call-with-input-file #$device
                                        (lambda (port)
                                          (false-if-exception (ttyname port)))))
                            (usleep 500)
                            (loop (- i 1))))

                        ;; Assume the VT is already in UTF-8 mode, thanks to
                        ;; the 'virtual-terminal' service.
                        ;;
                        ;; 'setfont' returns EX_OSERR (71) when an
                        ;; KDFONTOP ioctl fails, for example.  Like
                        ;; systemd's vconsole support, let's not treat
                        ;; this as an error.
                        (case (status:exit-val
                               (system* #$(file-append kbd "/bin/setfont")
                                        "-C" #$device #$font))
                          ((0 71) #t)
                          (else #f))))
             (stop #~(const #t))
             (respawn? #f)))))
       tty+font))

(define console-font-service-type
  (service-type (name 'console-fonts)
                (extensions
                 (list (service-extension shepherd-root-service-type
                                          console-font-shepherd-services)))
                (compose concatenate)
                (extend append)
                (description
                 "Install the given fonts on the specified ttys (fonts are per
virtual console on GNU/Linux).  The value of this service is a list of
tty/font pairs.  The font can be the name of a font provided by the @code{kbd}
package or any valid argument to @command{setfont}, as in this example:

@example
`((\"tty1\" . \"LatGrkCyr-8x16\")
  (\"tty2\" . ,(file-append
                 font-tamzen
                 \"/share/kbd/consolefonts/TamzenForPowerline10x20.psf\"))
  (\"tty3\" . ,(file-append
                 font-terminus
                 \"/share/consolefonts/ter-132n\"))) ; for HDPI
@end example\n")))

(define* (console-font-service tty #:optional (font "LatGrkCyr-8x16"))
  "This procedure is deprecated in favor of @code{console-font-service-type}.

Return a service that sets up Unicode support in @var{tty} and loads
@var{font} for that tty (fonts are per virtual console in Linux.)"
  (simple-service (symbol-append 'console-font- (string->symbol tty))
                  console-font-service-type `((,tty . ,font))))

(define %default-motd
  (plain-file "motd" "This is the GNU operating system, welcome!\n\n"))

(define-record-type* <login-configuration>
  login-configuration make-login-configuration
  login-configuration?
  (motd                   login-configuration-motd     ;file-like
                          (default %default-motd))
  ;; Allow empty passwords by default so that first-time users can log in when
  ;; the 'root' account has just been created.
  (allow-empty-passwords? login-configuration-allow-empty-passwords?
                          (default #t)))               ;Boolean

(define (login-pam-service config)
  "Return the list of PAM service needed for CONF."
  ;; Let 'login' be known to PAM.
  (list (unix-pam-service "login"
                          #:login-uid? #t
                          #:allow-empty-passwords?
                          (login-configuration-allow-empty-passwords? config)
                          #:motd
                          (login-configuration-motd config))))

(define login-service-type
  (service-type (name 'login)
                (extensions (list (service-extension pam-root-service-type
                                                     login-pam-service)))
                (default-value (login-configuration))
                (description
                 "Provide a console log-in service as specified by its
configuration value, a @code{login-configuration} object.")))

(define* (login-service #:optional (config (login-configuration)))
  "Return a service configure login according to @var{config}, which specifies
the message of the day, among other things."
  (service login-service-type config))

(define-record-type* <agetty-configuration>
  agetty-configuration make-agetty-configuration
  agetty-configuration?
  (agetty           agetty-configuration-agetty   ;file-like
                    (default util-linux))
  (tty              agetty-configuration-tty)     ;string | #f
  (term             agetty-term                   ;string | #f
                    (default #f))
  (baud-rate        agetty-baud-rate              ;string | #f
                    (default #f))
  (auto-login       agetty-auto-login             ;list of strings | #f
                    (default #f))
  (login-program    agetty-login-program          ;gexp
                    (default (file-append shadow "/bin/login")))
  (login-pause?     agetty-login-pause?           ;Boolean
                    (default #f))
  (eight-bits?      agetty-eight-bits?            ;Boolean
                    (default #f))
  (no-reset?        agetty-no-reset?              ;Boolean
                    (default #f))
  (remote?          agetty-remote?                ;Boolean
                    (default #f))
  (flow-control?    agetty-flow-control?          ;Boolean
                    (default #f))
  (host             agetty-host                   ;string | #f
                    (default #f))
  (no-issue?        agetty-no-issue?              ;Boolean
                    (default #f))
  (init-string      agetty-init-string            ;string | #f
                    (default #f))
  (no-clear?        agetty-no-clear?              ;Boolean
                    (default #f))
  (local-line       agetty-local-line             ;always | never | auto
                    (default #f))
  (extract-baud?    agetty-extract-baud?          ;Boolean
                    (default #f))
  (skip-login?      agetty-skip-login?            ;Boolean
                    (default #f))
  (no-newline?      agetty-no-newline?            ;Boolean
                    (default #f))
  (login-options    agetty-login-options          ;string | #f
                    (default #f))
  (chroot           agetty-chroot                 ;string | #f
                    (default #f))
  (hangup?          agetty-hangup?                ;Boolean
                    (default #f))
  (keep-baud?       agetty-keep-baud?             ;Boolean
                    (default #f))
  (timeout          agetty-timeout                ;integer | #f
                    (default #f))
  (detect-case?     agetty-detect-case?           ;Boolean
                    (default #f))
  (wait-cr?         agetty-wait-cr?               ;Boolean
                    (default #f))
  (no-hints?        agetty-no-hints?              ;Boolean
                    (default #f))
  (no-hostname?     agetty-no hostname?           ;Boolean
                    (default #f))
  (long-hostname?   agetty-long-hostname?         ;Boolean
                    (default #f))
  (erase-characters agetty-erase-characters       ;string | #f
                    (default #f))
  (kill-characters  agetty-kill-characters        ;string | #f
                    (default #f))
  (chdir            agetty-chdir                  ;string | #f
                    (default #f))
  (delay            agetty-delay                  ;integer | #f
                    (default #f))
  (nice             agetty-nice                   ;integer | #f
                    (default #f))
  ;; "Escape hatch" for passing arbitrary command-line arguments.
  (extra-options    agetty-extra-options          ;list of strings
                    (default '()))
  (shepherd-requirement agetty-shepherd-requirement  ;list of SHEPHERD requirements
                    (default '()))
;;; XXX Unimplemented for now!
;;; (issue-file     agetty-issue-file             ;file-like
;;;                 (default #f))
  )

(define (default-serial-port)
  "Return a gexp that determines a reasonable default serial port
to use as the tty.  This is primarily useful for headless systems."
  (with-imported-modules (source-module-closure
                          '((gnu build linux-boot))) ;for 'find-long-options'
    #~(begin
        ;; console=device,options
        ;; device: can be tty0, ttyS0, lp0, ttyUSB0 (serial).
        ;; options: BBBBPNF. P n|o|e, N number of bits,
        ;; F flow control (r RTS)
        (let* ((not-comma (char-set-complement (char-set #\,)))
               (command (linux-command-line))
               (agetty-specs (find-long-options "agetty.tty" command))
               (console-specs (filter (lambda (spec)
                                        (and (string-prefix? "tty" spec)
                                             (not (or
                                                   (string-prefix? "tty0" spec)
                                                   (string-prefix? "tty1" spec)
                                                   (string-prefix? "tty2" spec)
                                                   (string-prefix? "tty3" spec)
                                                   (string-prefix? "tty4" spec)
                                                   (string-prefix? "tty5" spec)
                                                   (string-prefix? "tty6" spec)
                                                   (string-prefix? "tty7" spec)
                                                   (string-prefix? "tty8" spec)
                                                   (string-prefix? "tty9" spec)))))
                                      (find-long-options "console" command)))
               (specs (append agetty-specs console-specs)))
          (match specs
            (() #f)
            ((spec _ ...)
             ;; Extract device name from first spec.
             (match (string-tokenize spec not-comma)
               ((device-name _ ...)
                device-name))))))))

(define agetty-shepherd-service
  (match-lambda
    (($ <agetty-configuration> agetty tty term baud-rate auto-login
        login-program login-pause? eight-bits? no-reset? remote? flow-control?
        host no-issue? init-string no-clear? local-line extract-baud?
        skip-login? no-newline? login-options chroot hangup? keep-baud? timeout
        detect-case? wait-cr? no-hints? no-hostname? long-hostname?
        erase-characters kill-characters chdir delay nice extra-options
        shepherd-requirement)
     (list
       (shepherd-service
         (documentation "Run agetty on a tty.")
         (provision (list (symbol-append 'term- (string->symbol (or tty "console")))))

         ;; Since the login prompt shows the host name, wait for the 'host-name'
         ;; service to be done.  Also wait for udev essentially so that the tty
         ;; text is not lost in the middle of kernel messages (see also
         ;; mingetty-shepherd-service).
         (requirement (cons* 'user-processes 'host-name 'udev
                             shepherd-requirement))

         (modules '((ice-9 match) (gnu build linux-boot)))
         (start
          (with-imported-modules  (source-module-closure
                                   '((gnu build linux-boot)))
            #~(lambda args
                (let ((defaulted-tty #$(or tty (default-serial-port))))
                  (apply
                   (if defaulted-tty
                       (make-forkexec-constructor
                        (list #$(file-append util-linux "/sbin/agetty")
                              #$@extra-options
                              #$@(if eight-bits?
                                     #~("--8bits")
                                     #~())
                              #$@(if no-reset?
                                     #~("--noreset")
                                     #~())
                              #$@(if remote?
                                     #~("--remote")
                                     #~())
                              #$@(if flow-control?
                                     #~("--flow-control")
                                     #~())
                              #$@(if host
                                     #~("--host" #$host)
                                     #~())
                              #$@(if no-issue?
                                     #~("--noissue")
                                     #~())
                              #$@(if init-string
                                     #~("--init-string" #$init-string)
                                     #~())
                              #$@(if no-clear?
                                     #~("--noclear")
                                     #~())
;;; FIXME This doesn't work as expected. According to agetty(8), if this option
;;; is not passed, then the default is 'auto'. However, in my tests, when that
;;; option is selected, agetty never presents the login prompt, and the
;;; term-ttyS0 service respawns every few seconds.
                              #$@(if local-line
                                     #~(#$(match local-line
                                            ('auto "--local-line=auto")
                                            ('always "--local-line=always")
                                            ('never "-local-line=never")))
                                     #~())
                              #$@(if tty
                                     #~()
                                     #~("--keep-baud"))
                              #$@(if extract-baud?
                                     #~("--extract-baud")
                                     #~())
                              #$@(if skip-login?
                                     #~("--skip-login")
                                     #~())
                              #$@(if no-newline?
                                     #~("--nonewline")
                                     #~())
                              #$@(if login-options
                                     #~("--login-options" #$login-options)
                                     #~())
                              #$@(if chroot
                                     #~("--chroot" #$chroot)
                                     #~())
                              #$@(if hangup?
                                     #~("--hangup")
                                     #~())
                              #$@(if keep-baud?
                                     #~("--keep-baud")
                                     #~())
                              #$@(if timeout
                                     #~("--timeout" #$(number->string timeout))
                                     #~())
                              #$@(if detect-case?
                                     #~("--detect-case")
                                     #~())
                              #$@(if wait-cr?
                                     #~("--wait-cr")
                                     #~())
                              #$@(if no-hints?
                                     #~("--nohints?")
                                     #~())
                              #$@(if no-hostname?
                                     #~("--nohostname")
                                     #~())
                              #$@(if long-hostname?
                                     #~("--long-hostname")
                                     #~())
                              #$@(if erase-characters
                                     #~("--erase-chars" #$erase-characters)
                                     #~())
                              #$@(if kill-characters
                                     #~("--kill-chars" #$kill-characters)
                                     #~())
                              #$@(if chdir
                                     #~("--chdir" #$chdir)
                                     #~())
                              #$@(if delay
                                     #~("--delay" #$(number->string delay))
                                     #~())
                              #$@(if nice
                                     #~("--nice" #$(number->string nice))
                                     #~())
                              #$@(if auto-login
                                     (list "--autologin" auto-login)
                                     '())
                              #$@(if login-program
                                     #~("--login-program" #$login-program)
                                     #~())
                              #$@(if login-pause?
                                     #~("--login-pause")
                                     #~())
                              defaulted-tty
                              #$@(if baud-rate
                                     #~(#$baud-rate)
                                     #~())
                              #$@(if term
                                     #~(#$term)
                                     #~())))
                       (const #f))                 ; never start.
                   args)))))
         (stop #~(make-kill-destructor)))))))

(define agetty-service-type
  (service-type (name 'agetty)
                (extensions (list (service-extension shepherd-root-service-type
                                                     agetty-shepherd-service)))
                (description
                 "Provide console login using the @command{agetty}
program.")))

(define* (agetty-service config)
  "Return a service to run agetty according to @var{config}, which specifies
the tty to run, among other things."
  (service agetty-service-type config))

(define-record-type* <mingetty-configuration>
  mingetty-configuration make-mingetty-configuration
  mingetty-configuration?
  (mingetty         mingetty-configuration-mingetty ;file-like
                    (default mingetty))
  (tty              mingetty-configuration-tty)     ;string
  (auto-login       mingetty-auto-login             ;string | #f
                    (default #f))
  (login-program    mingetty-login-program          ;gexp
                    (default #f))
  (login-pause?     mingetty-login-pause?           ;Boolean
                    (default #f))
  (clear-on-logout? mingetty-clear-on-logout?       ;Boolean
                    (default #t)))

(define mingetty-shepherd-service
  (match-lambda
    (($ <mingetty-configuration> mingetty tty auto-login login-program
                                 login-pause? clear-on-logout?)
     (list
      (shepherd-service
       (documentation "Run mingetty on an tty.")
       (provision (list (symbol-append 'term- (string->symbol tty))))

       ;; Since the login prompt shows the host name, wait for the 'host-name'
       ;; service to be done.  Also wait for udev essentially so that the tty
       ;; text is not lost in the middle of kernel messages (XXX).
       (requirement '(user-processes host-name udev virtual-terminal))

       (start  #~(make-forkexec-constructor
                  (list #$(file-append mingetty "/sbin/mingetty")

                        ;; Avoiding 'vhangup' allows us to avoid 'setfont'
                        ;; errors down the path where various ioctls get
                        ;; EIO--see 'hung_up_tty_ioctl' in driver/tty/tty_io.c
                        ;; in Linux.
                        "--nohangup" #$tty

                        #$@(if clear-on-logout?
                               #~()
                               #~("--noclear"))
                        #$@(if auto-login
                               #~("--autologin" #$auto-login)
                               #~())
                        #$@(if login-program
                               #~("--loginprog" #$login-program)
                               #~())
                        #$@(if login-pause?
                               #~("--loginpause")
                               #~()))))
       (stop   #~(make-kill-destructor)))))))

(define mingetty-service-type
  (service-type (name 'mingetty)
                (extensions (list (service-extension shepherd-root-service-type
                                                     mingetty-shepherd-service)))
                (description
                 "Provide console login using the @command{mingetty}
program.")))

(define* (mingetty-service config)
  "Return a service to run mingetty according to @var{config}, which specifies
the tty to run, among other things."
  (service mingetty-service-type config))

(define-record-type* <nscd-configuration> nscd-configuration
  make-nscd-configuration
  nscd-configuration?
  (log-file    nscd-configuration-log-file        ;string
               (default "/var/log/nscd.log"))
  (debug-level nscd-debug-level                   ;integer
               (default 0))
  ;; TODO: See nscd.conf in glibc for other options to add.
  (caches     nscd-configuration-caches           ;list of <nscd-cache>
              (default %nscd-default-caches))
  (name-services nscd-configuration-name-services ;list of file-like
                 (default '()))
  (glibc      nscd-configuration-glibc            ;file-like
              (default glibc)))

(define-record-type* <nscd-cache> nscd-cache make-nscd-cache
  nscd-cache?
  (database              nscd-cache-database)              ;symbol
  (positive-time-to-live nscd-cache-positive-time-to-live) ;integer
  (negative-time-to-live nscd-cache-negative-time-to-live
                         (default 20))             ;integer
  (suggested-size        nscd-cache-suggested-size ;integer ("default module
                                                   ;of hash table")
                         (default 211))
  (check-files?          nscd-cache-check-files?  ;Boolean
                         (default #t))
  (persistent?           nscd-cache-persistent?   ;Boolean
                         (default #t))
  (shared?               nscd-cache-shared?       ;Boolean
                         (default #t))
  (max-database-size     nscd-cache-max-database-size ;integer
                         (default (* 32 (expt 2 20))))
  (auto-propagate?       nscd-cache-auto-propagate? ;Boolean
                         (default #t)))

(define %nscd-default-caches
  ;; Caches that we want to enable by default.  Note that when providing an
  ;; empty nscd.conf, all caches are disabled.
  (list (nscd-cache (database 'hosts)

                    ;; Aggressively cache the host name cache to improve
                    ;; privacy and resilience.
                    (positive-time-to-live (* 3600 12))
                    (negative-time-to-live 20)
                    (persistent? #t))

        (nscd-cache (database 'services)

                    ;; Services are unlikely to change, so we can be even more
                    ;; aggressive.
                    (positive-time-to-live (* 3600 24))
                    (negative-time-to-live 3600)
                    (check-files? #t)             ;check /etc/services changes
                    (persistent? #t))))

(define %nscd-default-configuration
  ;; Default nscd configuration.
  (nscd-configuration))

(define (nscd.conf-file config)
  "Return the @file{nscd.conf} configuration file for @var{config}, an
@code{<nscd-configuration>} object."
  (define cache->config
    (match-lambda
      (($ <nscd-cache> (= symbol->string database)
                       positive-ttl negative-ttl size check-files?
                       persistent? shared? max-size propagate?)
       (string-append "\nenable-cache\t" database "\tyes\n"

                      "positive-time-to-live\t" database "\t"
                      (number->string positive-ttl) "\n"
                      "negative-time-to-live\t" database "\t"
                      (number->string negative-ttl) "\n"
                      "suggested-size\t" database "\t"
                      (number->string size) "\n"
                      "check-files\t" database "\t"
                      (if check-files? "yes\n" "no\n")
                      "persistent\t" database "\t"
                      (if persistent? "yes\n" "no\n")
                      "shared\t" database "\t"
                      (if shared? "yes\n" "no\n")
                      "max-db-size\t" database "\t"
                      (number->string max-size) "\n"
                      "auto-propagate\t" database "\t"
                      (if propagate? "yes\n" "no\n")))))

  (match config
    (($ <nscd-configuration> log-file debug-level caches)
     (plain-file "nscd.conf"
                 (string-append "\
# Configuration of libc's name service cache daemon (nscd).\n\n"
                                (if log-file
                                    (string-append "logfile\t" log-file)
                                    "")
                                "\n"
                                (if debug-level
                                    (string-append "debug-level\t"
                                                   (number->string debug-level))
                                    "")
                                "\n"
                                (string-concatenate
                                 (map cache->config caches)))))))

(define (nscd-action-procedure nscd config option)
  ;; XXX: This is duplicated from mcron; factorize.
  #~(lambda (_ . args)
      ;; Run 'nscd' in a pipe so we can explicitly redirect its output to
      ;; 'current-output-port', which at this stage is bound to the client
      ;; connection.
      (let ((pipe (apply open-pipe* OPEN_READ #$nscd
                         "-f" #$config #$option args)))
        (let loop ()
          (match (read-line pipe 'concat)
            ((? eof-object?)
             (catch 'system-error
               (lambda ()
                 (zero? (close-pipe pipe)))
               (lambda args
                 ;; There's a race with the SIGCHLD handler, which could
                 ;; call 'waitpid' before 'close-pipe' above does.  If we
                 ;; get ECHILD, that means we lost the race; in that case, we
                 ;; cannot tell what the exit code was (FIXME).
                 (or (= ECHILD (system-error-errno args))
                     (apply throw args)))))
            (line
             (display line)
             (loop)))))))

(define (nscd-actions nscd config)
  "Return Shepherd actions for NSCD."
  ;; Make this functionality available as actions because that's a simple way
  ;; to run the right 'nscd' binary with the right config file.
  (list (shepherd-action
         (name 'statistics)
         (documentation "Display statistics about nscd usage.")
         (procedure (nscd-action-procedure nscd config "--statistics")))
        (shepherd-action
         (name 'invalidate)
         (documentation
          "Invalidate the given cache--e.g., 'hosts' for host name lookups.")
         (procedure (nscd-action-procedure nscd config "--invalidate")))))

(define (nscd-shepherd-service config)
  "Return a shepherd service for CONFIG, an <nscd-configuration> object."
  (let ((nscd          (file-append (nscd-configuration-glibc config)
                                    "/sbin/nscd"))
        (nscd.conf     (nscd.conf-file config))
        (name-services (nscd-configuration-name-services config)))
    (list (shepherd-service
           (documentation "Run libc's name service cache daemon (nscd).")
           (provision '(nscd))
           (requirement '(user-processes))
           (start #~(make-forkexec-constructor
                     (list #$nscd "-f" #$nscd.conf "--foreground")

                     ;; Wait for the PID file.  However, the PID file is
                     ;; written before nscd is actually listening on its
                     ;; socket (XXX).
                     #:pid-file "/var/run/nscd/nscd.pid"

                     #:environment-variables
                     (list (string-append "LD_LIBRARY_PATH="
                                          (string-join
                                           (map (lambda (dir)
                                                  (string-append dir "/lib"))
                                                (list #$@name-services))
                                           ":")))))
           (stop #~(make-kill-destructor))
           (modules `((ice-9 popen)               ;for the actions
                      (ice-9 rdelim)
                      (ice-9 match)
                      ,@%default-modules))
           (actions (nscd-actions nscd nscd.conf))))))

(define nscd-activation
  ;; Actions to take before starting nscd.
  #~(begin
      (use-modules (guix build utils))
      (mkdir-p "/var/run/nscd")
      (mkdir-p "/var/db/nscd")                    ;for the persistent cache

      ;; In libc 2.25 nscd uses inotify to watch /etc/resolv.conf, but only if
      ;; that file exists when it is started.  Thus create it here.  Note: on
      ;; some systems, such as when NetworkManager is used, /etc/resolv.conf
      ;; is a symlink, hence 'lstat'.
      (unless (false-if-exception (lstat "/etc/resolv.conf"))
        (call-with-output-file "/etc/resolv.conf"
          (lambda (port)
            (display "# This is a placeholder.\n" port))))))

(define nscd-service-type
  (service-type (name 'nscd)
                (extensions
                 (list (service-extension activation-service-type
                                          (const nscd-activation))
                       (service-extension shepherd-root-service-type
                                          nscd-shepherd-service)))

                ;; This can be extended by providing additional name services
                ;; such as nss-mdns.
                (compose concatenate)
                (extend (lambda (config name-services)
                          (nscd-configuration
                           (inherit config)
                           (name-services (append
                                           (nscd-configuration-name-services config)
                                           name-services)))))
                (default-value %nscd-default-configuration)
                (description
                 "Runs libc's @dfn{name service cache daemon} (nscd) with the
given configuration---an @code{<nscd-configuration>} object.  @xref{Name
Service Switch}, for an example.")))

(define* (nscd-service #:optional (config %nscd-default-configuration))
  "Return a service that runs libc's name service cache daemon (nscd) with the
given @var{config}---an @code{<nscd-configuration>} object.  @xref{Name
Service Switch}, for an example."
  (service nscd-service-type config))


(define-record-type* <syslog-configuration>
  syslog-configuration  make-syslog-configuration
  syslog-configuration?
  (syslogd              syslog-configuration-syslogd
                        (default (file-append inetutils "/libexec/syslogd")))
  (config-file          syslog-configuration-config-file
                        (default %default-syslog.conf)))

(define syslog-service-type
  (shepherd-service-type
   'syslog
   (lambda (config)
     (shepherd-service
      (documentation "Run the syslog daemon (syslogd).")
      (provision '(syslogd))
      (requirement '(user-processes))
      (start #~(let ((spawn (make-forkexec-constructor
                             (list #$(syslog-configuration-syslogd config)
                                   "--rcfile"
                                   #$(syslog-configuration-config-file config))
                             #:pid-file "/var/run/syslog.pid")))
                 (lambda ()
                   ;; Set the umask such that file permissions are #o640.
                   (let ((mask (umask #o137))
                         (pid  (spawn)))
                     (umask mask)
                     pid))))
      (stop #~(make-kill-destructor))))
   (description "Run the syslog daemon, @command{syslogd}, which is
responsible for logging system messages.")))

;; Snippet adapted from the GNU inetutils manual.
(define %default-syslog.conf
  (plain-file "syslog.conf" "
     # Log all error messages, authentication messages of
     # level notice or higher and anything of level err or
     # higher to the console.
     # Don't log private authentication messages!
     *.alert;auth.notice;authpriv.none       /dev/console

     # Log anything (except mail) of level info or higher.
     # Don't log private authentication messages!
     *.info;mail.none;authpriv.none          /var/log/messages

     # Like /var/log/messages, but also including \"debug\"-level logs.
     *.debug;mail.none;authpriv.none         /var/log/debug

     # Same, in a different place.
     *.info;mail.none;authpriv.none          /dev/tty12

     # The authpriv file has restricted access.
     authpriv.*                              /var/log/secure

     # Log all the mail messages in one place.
     mail.*                                  /var/log/maillog
"))

(define* (syslog-service #:optional (config (syslog-configuration)))
  "Return a service that runs @command{syslogd} and takes
@var{<syslog-configuration>} as a parameter.

@xref{syslogd invocation,,, inetutils, GNU Inetutils}, for more
information on the configuration file syntax."
  (service syslog-service-type config))


(define pam-limits-service-type
  (let ((security-limits
         ;; Create /etc/security containing the provided "limits.conf" file.
         (lambda (limits-file)
           `(("security/limits.conf"
              ,limits-file))))
        (pam-extension
         (lambda (pam)
           (let ((pam-limits (pam-entry
                              (control "required")
                              (module "pam_limits.so")
                              (arguments '("conf=/etc/security/limits.conf")))))
             (if (member (pam-service-name pam)
                         '("login" "su" "slim" "gdm-password" "sddm"))
                 (pam-service
                  (inherit pam)
                  (session (cons pam-limits
                                 (pam-service-session pam))))
                 pam)))))
    (service-type
     (name 'limits)
     (extensions
      (list (service-extension etc-service-type security-limits)
            (service-extension pam-root-service-type
                               (lambda _ (list pam-extension)))))
     (description
      "Install the specified resource usage limits by populating
@file{/etc/security/limits.conf} and using the @code{pam_limits}
authentication module."))))

(define* (pam-limits-service #:optional (limits '()))
  "Return a service that makes selected programs respect the list of
pam-limits-entry specified in LIMITS via pam_limits.so."
  (service pam-limits-service-type
           (plain-file "limits.conf"
                       (string-join (map pam-limits-entry->string limits)
                                    "\n"))))


;;;
;;; Guix services.
;;;

(define* (guix-build-accounts count #:key
                              (group "guixbuild")
                              (shadow shadow))
  "Return a list of COUNT user accounts for Guix build users with the given
GID."
  (unfold (cut > <> count)
          (lambda (n)
            (user-account
             (name (format #f "guixbuilder~2,'0d" n))
             (system? #t)
             (group group)

             ;; guix-daemon expects GROUP to be listed as a
             ;; supplementary group too:
             ;; <http://lists.gnu.org/archive/html/bug-guix/2013-01/msg00239.html>.
             (supplementary-groups (list group "kvm"))

             (comment (format #f "Guix Build User ~2d" n))
             (home-directory "/var/empty")
             (shell (file-append shadow "/sbin/nologin"))))
          1+
          1))

(define not-config?
  ;; Select (guix …) and (gnu …) modules, except (guix config).
  (match-lambda
    (('guix 'config) #f)
    (('guix rest ...) #t)
    (('gnu rest ...) #t)
    (rest #f)))

(define (substitute-key-authorization keys guix)
  "Return a gexp with code to register KEYS, a list of files containing 'guix
archive' public keys, with GUIX."
  (define default-acl
    (with-extensions (list guile-gcrypt)
      (with-imported-modules `(((guix config) => ,(make-config.scm))
                               ,@(source-module-closure '((guix pki))
                                                        #:select? not-config?))
        (computed-file "acl"
                       #~(begin
                           (use-modules (guix pki)
                                        (gcrypt pk-crypto)
                                        (ice-9 rdelim))

                           (define keys
                             (map (lambda (file)
                                    (call-with-input-file file
                                      (compose string->canonical-sexp
                                               read-string)))
                                  '(#$@keys)))

                           (call-with-output-file #$output
                             (lambda (port)
                               (write-acl (public-keys->acl keys)
                                          port))))))))

  (with-imported-modules '((guix build utils))
    #~(begin
        (use-modules (guix build utils))

        ;; If the ACL already exists, move it out of the way.  Create a backup
        ;; if it's a regular file: it's likely that the user manually updated
        ;; it with 'guix archive --authorize'.
        (if (file-exists? "/etc/guix/acl")
            (if (and (symbolic-link? "/etc/guix/acl")
                     (store-file-name? (readlink "/etc/guix/acl")))
                (delete-file "/etc/guix/acl")
                (rename-file "/etc/guix/acl" "/etc/guix/acl.bak"))
            (mkdir-p "/etc/guix"))

        ;; Installed the declared ACL.
        (symlink #+default-acl "/etc/guix/acl"))))

(define %default-authorized-guix-keys
  ;; List of authorized substitute keys.
  (list (file-append guix "/share/guix/berlin.guix.gnu.org.pub")
        (file-append guix "/share/guix/bordeaux.guix.gnu.org.pub")))

(define-record-type* <guix-configuration>
  guix-configuration make-guix-configuration
  guix-configuration?
  (guix             guix-configuration-guix       ;file-like
                    (default guix))
  (build-group      guix-configuration-build-group ;string
                    (default "guixbuild"))
  (build-accounts   guix-configuration-build-accounts ;integer
                    (default 10))
  (authorize-key?   guix-configuration-authorize-key? ;Boolean
                    (default #t))
  (authorized-keys  guix-configuration-authorized-keys ;list of gexps
                    (default %default-authorized-guix-keys))
  (use-substitutes? guix-configuration-use-substitutes? ;Boolean
                    (default #t))
  (substitute-urls  guix-configuration-substitute-urls ;list of strings
                    (default %default-substitute-urls))
  (chroot-directories guix-configuration-chroot-directories ;list of file-like/strings
                      (default '()))
  (max-silent-time  guix-configuration-max-silent-time ;integer
                    (default 0))
  (timeout          guix-configuration-timeout    ;integer
                    (default 0))
  (log-compression  guix-configuration-log-compression
                    (default 'gzip))
  (discover?        guix-configuration-discover?
                    (default #f))
  (extra-options    guix-configuration-extra-options ;list of strings
                    (default '()))
  (log-file         guix-configuration-log-file   ;string
                    (default "/var/log/guix-daemon.log"))
  (http-proxy       guix-http-proxy               ;string | #f
                    (default #f))
  (tmpdir           guix-tmpdir                   ;string | #f
                    (default #f)))

(define %default-guix-configuration
  (guix-configuration))

(define shepherd-set-http-proxy-action
  ;; Shepherd action to change the HTTP(S) proxy.
  (shepherd-action
   (name 'set-http-proxy)
   (documentation
    "Change the HTTP(S) proxy used by 'guix-daemon' and restart it.")
   (procedure #~(lambda* (_ #:optional proxy)
                  (let ((environment (environ)))
                    ;; A bit of a hack: communicate PROXY to the 'start'
                    ;; method via environment variables.
                    (if proxy
                        (begin
                          (format #t "changing HTTP/HTTPS \
proxy of 'guix-daemon' to ~s...~%"
                                  proxy)
                          (setenv "http_proxy" proxy))
                        (begin
                          (format #t "clearing HTTP/HTTPS \
proxy of 'guix-daemon'...~%")
                          (unsetenv "http_proxy")))
                    (action 'guix-daemon 'restart)
                    (environ environment)
                    #t)))))

(define shepherd-discover-action
  ;; Shepherd action to enable or disable substitute servers discovery.
  (shepherd-action
   (name 'discover)
   (documentation
    "Enable or disable substitute servers discovery and restart the
'guix-daemon'.")
   (procedure #~(lambda* (_ status)
                  (let ((environment (environ)))
                    (if (and status
                             (string=? status "on"))
                        (begin
                          (format #t "enable substitute servers discovery~%")
                          (setenv "discover" "on"))
                        (begin
                          (format #t "disable substitute servers discovery~%")
                          (unsetenv "discover")))
                    (action 'guix-daemon 'restart)
                    (environ environment)
                    #t)))))

(define (guix-shepherd-service config)
  "Return a <shepherd-service> for the Guix daemon service with CONFIG."
  (match-record config <guix-configuration>
    (guix build-group build-accounts authorize-key? authorized-keys
          use-substitutes? substitute-urls max-silent-time timeout
          log-compression discover? extra-options log-file
          http-proxy tmpdir chroot-directories)
    (list (shepherd-service
           (documentation "Run the Guix daemon.")
           (provision '(guix-daemon))
           (requirement '(user-processes))
           (actions (list shepherd-set-http-proxy-action
                          shepherd-discover-action))
           (modules '((srfi srfi-1)
                      (ice-9 match)
                      (gnu build shepherd)))
           (start
            (with-imported-modules `(((guix config) => ,(make-config.scm))
                                     ,@(source-module-closure
                                        '((gnu build shepherd))
                                        #:select? not-config?))
              #~(lambda args
                  (define proxy
                    ;; HTTP/HTTPS proxy.  The 'http_proxy' variable is set by
                    ;; the 'set-http-proxy' action.
                    (or (getenv "http_proxy") #$http-proxy))

                  (define discover?
                    (or (getenv "discover") #$discover?))

                  ;; Start the guix-daemon from a container, when supported,
                  ;; to solve an installation issue. See the comment below for
                  ;; more details.
                  (fork+exec-command/container
                   (cons* #$(file-append guix "/bin/guix-daemon")
                          "--build-users-group" #$build-group
                          "--max-silent-time"
                          #$(number->string max-silent-time)
                          "--timeout" #$(number->string timeout)
                          "--log-compression"
                          #$(symbol->string log-compression)
                          #$@(if use-substitutes?
                                 '()
                                 '("--no-substitutes"))
                          (string-append "--discover="
                                         (if discover? "yes" "no"))
                          "--substitute-urls" #$(string-join substitute-urls)
                          #$@extra-options

                          ;; Add CHROOT-DIRECTORIES and all their dependencies
                          ;; (if these are store items) to the chroot.
                          (append-map
                           (lambda (file)
                             (append-map (lambda (directory)
                                           (list "--chroot-directory"
                                                 directory))
                                         (call-with-input-file file
                                           read)))
                           '#$(map references-file
                                   chroot-directories)))

                   ;; When running the installer, we need guix-daemon to
                   ;; operate from within the same MNT namespace as the
                   ;; installation container. In that case only, enter the
                   ;; namespace of the process PID passed as start argument.
                   ;; Otherwise, for symmetry purposes enter the caller
                   ;; namespaces which is a no-op.
                   #:pid (match args
                           ((pid) (string->number pid))
                           (else (getpid)))

                   #:environment-variables
                   (append (list #$@(if tmpdir
                                        (list (string-append "TMPDIR=" tmpdir))
                                        '())

                                 ;; Make sure we run in a UTF-8 locale so that
                                 ;; 'guix offload' correctly restores nars
                                 ;; that contain UTF-8 file names such as
                                 ;; 'nss-certs'.  See
                                 ;; <https://bugs.gnu.org/32942>.
                                 (string-append "GUIX_LOCPATH="
                                                #$glibc-utf8-locales
                                                "/lib/locale")
                                 "LC_ALL=en_US.utf8"
                                 ;; Make 'tar' and 'gzip' available so
                                 ;; that 'guix perform-download' can use
                                 ;; them when downloading from Software
                                 ;; Heritage via '(guix swh)'.
                                 (string-append "PATH="
                                                #$(file-append tar "/bin") ":"
                                                #$(file-append gzip "/bin")))
                           (if proxy
                               (list (string-append "http_proxy=" proxy)
                                     (string-append "https_proxy=" proxy))
                               '()))

                   #:log-file #$log-file))))
           (stop #~(make-kill-destructor))))))

(define (guix-accounts config)
  "Return the user accounts and user groups for CONFIG."
  (match config
    (($ <guix-configuration> _ build-group build-accounts)
     (cons (user-group
            (name build-group)
            (system? #t)

            ;; Use a fixed GID so that we can create the store with the right
            ;; owner.
            (id 30000))
           (guix-build-accounts build-accounts
                                #:group build-group)))))

(define (guix-activation config)
  "Return the activation gexp for CONFIG."
  (match-record config <guix-configuration>
    (guix authorize-key? authorized-keys)
    #~(begin
        ;; Assume that the store has BUILD-GROUP as its group.  We could
        ;; otherwise call 'chown' here, but the problem is that on a COW overlayfs,
        ;; chown leads to an entire copy of the tree, which is a bad idea.

        ;; Generate a key pair and optionally authorize substitute server keys.
        (unless (file-exists? "/etc/guix/signing-key.pub")
          (system* #$(file-append guix "/bin/guix") "archive"
                   "--generate-key"))

        #$(if authorize-key?
              (substitute-key-authorization authorized-keys guix)
              #~#f))))

(define* (references-file item #:optional (name "references"))
  "Return a file that contains the list of references of ITEM."
  (if (struct? item)                              ;lowerable object
      (computed-file name
                     (with-extensions (list guile-gcrypt) ;for store-copy
                       (with-imported-modules (source-module-closure
                                               '((guix build store-copy)))
                         #~(begin
                             (use-modules (guix build store-copy))

                             (call-with-output-file #$output
                               (lambda (port)
                                 (write (map store-info-item
                                             (call-with-input-file "graph"
                                               read-reference-graph))
                                        port))))))
                     #:options `(#:local-build? #f
                                 #:references-graphs (("graph" ,item))))
      (plain-file name "()")))

(define guix-service-type
  (service-type
   (name 'guix)
   (extensions
    (list (service-extension shepherd-root-service-type guix-shepherd-service)
          (service-extension account-service-type guix-accounts)
          (service-extension activation-service-type guix-activation)
          (service-extension profile-service-type
                             (compose list guix-configuration-guix))))

   ;; Extensions can specify extra directories to add to the build chroot.
   (compose concatenate)
   (extend (lambda (config directories)
             (guix-configuration
              (inherit config)
              (chroot-directories
               (append (guix-configuration-chroot-directories config)
                       directories)))))

   (default-value (guix-configuration))
   (description
    "Run the build daemon of GNU@tie{}Guix, aka. @command{guix-daemon}.")))


(define-record-type* <guix-publish-configuration>
  guix-publish-configuration make-guix-publish-configuration
  guix-publish-configuration?
  (guix    guix-publish-configuration-guix        ;file-like
           (default guix))
  (port    guix-publish-configuration-port        ;number
           (default 80))
  (host    guix-publish-configuration-host        ;string
           (default "localhost"))
  (advertise? guix-publish-advertise?       ;boolean
              (default #f))
  (compression       guix-publish-configuration-compression
                     (thunked)
                     (default (default-compression this-record
                                (current-source-location))))
  (compression-level %guix-publish-configuration-compression-level ;deprecated
                     (default #f))
  (nar-path    guix-publish-configuration-nar-path ;string
               (default "nar"))
  (cache       guix-publish-configuration-cache   ;#f | string
               (default #f))
  (cache-bypass-threshold guix-publish-configuration-cache-bypass-threshold
                          (default (* 10 (expt 2 20)))) ;integer
  (workers     guix-publish-configuration-workers ;#f | integer
               (default #f))
  (ttl         guix-publish-configuration-ttl     ;#f | integer
               (default #f))
  (negative-ttl guix-publish-configuration-negative-ttl ;#f | integer
                (default #f)))

(define-deprecated (guix-publish-configuration-compression-level config)
  "Return a compression level, the old way."
  (match (guix-publish-configuration-compression config)
    (((_ level) _ ...) level)))

(define (default-compression config properties)
  "Return the default 'guix publish' compression according to CONFIG, and
raise a deprecation warning if the 'compression-level' field was used."
  (match (%guix-publish-configuration-compression-level config)
    (#f
     ;; Default to low compression levels when there's no cache so that users
     ;; get good bandwidth by default.
     (if (guix-publish-configuration-cache config)
         '(("gzip" 5) ("zstd" 19))
         '(("gzip" 3) ("zstd" 3))))               ;zstd compresses faster
    (level
     (warn-about-deprecation 'compression-level properties
                             #:replacement 'compression)
     `(("gzip" ,level)))))

(define (guix-publish-shepherd-service config)
  (define (config->compression-options config)
    (match (guix-publish-configuration-compression config)
      (()                                   ;empty list means "no compression"
       '("-C0"))
      (lst
       (append-map (match-lambda
                     ((type level)
                      `("-C" ,(string-append type ":"
                                             (number->string level)))))
                   lst))))

  (match-record config <guix-publish-configuration>
    (guix port host nar-path cache workers ttl negative-ttl
          cache-bypass-threshold advertise?)
    (list (shepherd-service
           (provision '(guix-publish))
           (requirement `(user-processes
                          guix-daemon
                          ,@(if advertise? '(avahi-daemon) '())))
           (start #~(make-forkexec-constructor
                     (list #$(file-append guix "/bin/guix")
                           "publish" "-u" "guix-publish"
                           "-p" #$(number->string port)
                           #$@(config->compression-options config)
                           (string-append "--nar-path=" #$nar-path)
                           (string-append "--listen=" #$host)
                           #$@(if advertise?
                                  #~("--advertise")
                                  #~())
                           #$@(if workers
                                  #~((string-append "--workers="
                                                    #$(number->string
                                                       workers)))
                                  #~())
                           #$@(if ttl
                                  #~((string-append "--ttl="
                                                    #$(number->string ttl)
                                                    "s"))
                                  #~())
                           #$@(if negative-ttl
                                  #~((string-append "--negative-ttl="
                                                    #$(number->string negative-ttl)
                                                    "s"))
                                  #~())
                           #$@(if cache
                                  #~((string-append "--cache=" #$cache)
                                     #$(string-append
                                        "--cache-bypass-threshold="
                                        (number->string
                                         cache-bypass-threshold)))
                                  #~()))

                     ;; Make sure we run in a UTF-8 locale so we can produce
                     ;; nars for packages that contain UTF-8 file names such
                     ;; as 'nss-certs'.  See <https://bugs.gnu.org/26948>.
                     #:environment-variables
                     (list (string-append "GUIX_LOCPATH="
                                          #$glibc-utf8-locales "/lib/locale")
                           "LC_ALL=en_US.utf8")
                     #:log-file "/var/log/guix-publish.log"))
           (stop #~(make-kill-destructor))))))

(define %guix-publish-accounts
  (list (user-group (name "guix-publish") (system? #t))
        (user-account
         (name "guix-publish")
         (group "guix-publish")
         (system? #t)
         (comment "guix publish user")
         (home-directory "/var/empty")
         (shell (file-append shadow "/sbin/nologin")))))

(define %guix-publish-log-rotations
  (list (log-rotation
         (files (list "/var/log/guix-publish.log")))))

(define (guix-publish-activation config)
  (let ((cache (guix-publish-configuration-cache config)))
    (if cache
        (with-imported-modules '((guix build utils))
          #~(begin
              (use-modules (guix build utils))

              (mkdir-p #$cache)
              (let* ((pw  (getpw "guix-publish"))
                     (uid (passwd:uid pw))
                     (gid (passwd:gid pw)))
                (chown #$cache uid gid))))
        #t)))

(define guix-publish-service-type
  (service-type (name 'guix-publish)
                (extensions
                 (list (service-extension shepherd-root-service-type
                                          guix-publish-shepherd-service)
                       (service-extension account-service-type
                                          (const %guix-publish-accounts))
                       (service-extension rottlog-service-type
                                          (const %guix-publish-log-rotations))
                       (service-extension activation-service-type
                                          guix-publish-activation)))
                (default-value (guix-publish-configuration))
                (description
                 "Add a Shepherd service running @command{guix publish}, a
command that allows you to share pre-built binaries with others over HTTP.")))


;;;
;;; Udev.
;;;

(define-record-type* <udev-configuration>
  udev-configuration make-udev-configuration
  udev-configuration?
  (udev   udev-configuration-udev                 ;file-like
          (default eudev))
  (rules  udev-configuration-rules                ;list of file-like
          (default '())))

(define (udev-rules-union packages)
  "Return the union of the @code{lib/udev/rules.d} directories found in each
item of @var{packages}."
  (define build
    (with-imported-modules '((guix build union)
                             (guix build utils))
      #~(begin
          (use-modules (guix build union)
                       (guix build utils)
                       (srfi srfi-1)
                       (srfi srfi-26))

          (define %standard-locations
            '("/lib/udev/rules.d" "/libexec/udev/rules.d"))

          (define (rules-sub-directory directory)
            ;; Return the sub-directory of DIRECTORY containing udev rules, or
            ;; #f if none was found.
            (find directory-exists?
                  (map (cut string-append directory <>) %standard-locations)))

          (union-build #$output
                       (filter-map rules-sub-directory '#$packages)))))

  (computed-file "udev-rules" build))

(define (udev-rule file-name contents)
  "Return a directory with a udev rule file FILE-NAME containing CONTENTS."
  (computed-file file-name
                 (with-imported-modules '((guix build utils))
                   #~(begin
                       (use-modules (guix build utils))

                       (define rules.d
                         (string-append #$output "/lib/udev/rules.d"))

                       (mkdir-p rules.d)
                       (call-with-output-file
                           (string-append rules.d "/" #$file-name)
                         (lambda (port)
                           (display #$contents port)))))))

(define (file->udev-rule file-name file)
  "Return a directory with a udev rule file FILE-NAME which is a copy of FILE."
  (computed-file file-name
                 (with-imported-modules '((guix build utils))
                   #~(begin
                       (use-modules (guix build utils))

                       (define rules.d
                         (string-append #$output "/lib/udev/rules.d"))

                       (define file-copy-dest
                         (string-append rules.d "/" #$file-name))

                       (mkdir-p rules.d)
                       (copy-file #$file file-copy-dest)))))

(define kvm-udev-rule
  ;; Return a directory with a udev rule that changes the group of /dev/kvm to
  ;; "kvm" and makes it #o660.  Apparently QEMU-KVM used to ship this rule,
  ;; but now we have to add it by ourselves.

  ;; Build users are part of the "kvm" group, so we can fearlessly make
  ;; /dev/kvm 660 (see <http://bugs.gnu.org/18994>, for background.)
  (udev-rule "90-kvm.rules"
             "KERNEL==\"kvm\", GROUP=\"kvm\", MODE=\"0660\"\n"))

(define udev-shepherd-service
  ;; Return a <shepherd-service> for UDEV with RULES.
  (match-lambda
    (($ <udev-configuration> udev)
     (list
      (shepherd-service
       (provision '(udev))

       ;; Udev needs /dev to be a 'devtmpfs' mount so that new device nodes can
       ;; be added: see
       ;; <http://www.linuxfromscratch.org/lfs/view/development/chapter07/udev.html>.
       (requirement '(root-file-system))

       (documentation "Populate the /dev directory, dynamically.")
       (start
        (with-imported-modules (source-module-closure
                                '((gnu build linux-boot)))
          #~(lambda ()
              (define udevd
                ;; 'udevd' from eudev.
                #$(file-append udev "/sbin/udevd"))

              (define (wait-for-udevd)
                ;; Wait until someone's listening on udevd's control
                ;; socket.
                (let ((sock (socket AF_UNIX SOCK_SEQPACKET 0)))
                  (let try ()
                    (catch 'system-error
                      (lambda ()
                        (connect sock PF_UNIX "/run/udev/control")
                        (close-port sock))
                      (lambda args
                        (format #t "waiting for udevd...~%")
                        (usleep 500000)
                        (try))))))

              ;; Allow udev to find the modules.
              (setenv "LINUX_MODULE_DIRECTORY"
                      "/run/booted-system/kernel/lib/modules")

              (let* ((kernel-release
                      (utsname:release (uname)))
                     (linux-module-directory
                      (getenv "LINUX_MODULE_DIRECTORY"))
                     (directory
                      (string-append linux-module-directory "/"
                                     kernel-release))
                     (old-umask (umask #o022)))
                ;; If we're in a container, DIRECTORY might not exist,
                ;; for instance because the host runs a different
                ;; kernel.  In that case, skip it; we'll just miss a few
                ;; nodes like /dev/fuse.
                (when (file-exists? directory)
                  (make-static-device-nodes directory))
                (umask old-umask))

              (let ((pid (fork+exec-command
                          (list udevd)
                          #:environment-variables
                          (cons*
                           ;; The first one is for udev, the second one for
                           ;; eudev.
                           "UDEV_CONFIG_FILE=/etc/udev/udev.conf"
                           "EUDEV_RULES_DIRECTORY=/etc/udev/rules.d"
                           (string-append "LINUX_MODULE_DIRECTORY="
                                          (getenv "LINUX_MODULE_DIRECTORY"))
                           (default-environment-variables)))))
                ;; Wait until udevd is up and running.  This appears to
                ;; be needed so that the events triggered below are
                ;; actually handled.
                (wait-for-udevd)

                ;; Trigger device node creation.
                (system* #$(file-append udev "/bin/udevadm")
                         "trigger" "--action=add")

                ;; Wait for things to settle down.
                (system* #$(file-append udev "/bin/udevadm")
                         "settle")
                pid))))
       (stop #~(make-kill-destructor))

       ;; When halting the system, 'udev' is actually killed by
       ;; 'user-processes', i.e., before its own 'stop' method was called.
       ;; Thus, make sure it is not respawned.
       (respawn? #f)
       ;; We need additional modules.
       (modules `((gnu build linux-boot)        ;'make-static-device-nodes'
                  ,@%default-modules)))))))

(define udev.conf
  (computed-file "udev.conf"
                 #~(call-with-output-file #$output
                     (lambda (port)
                       (format port "udev_rules=\"/etc/udev/rules.d\"~%")))))

(define udev-etc
  (match-lambda
    (($ <udev-configuration> udev rules)
     `(("udev"
        ,(file-union
          "udev" `(("udev.conf" ,udev.conf)
                   ("rules.d" ,(udev-rules-union (cons* udev kvm-udev-rule
                                                        rules))))))))))

(define udev-service-type
  (service-type (name 'udev)
                (extensions
                 (list (service-extension shepherd-root-service-type
                                          udev-shepherd-service)
                       (service-extension etc-service-type udev-etc)))
                (compose concatenate)           ;concatenate the list of rules
                (extend (lambda (config rules)
                          (match config
                            (($ <udev-configuration> udev initial-rules)
                             (udev-configuration
                              (udev udev)
                              (rules (append initial-rules rules)))))))
                (default-value (udev-configuration))
                (description
                 "Run @command{udev}, which populates the @file{/dev}
directory dynamically.  Get extra rules from the packages listed in the
@code{rules} field of its value, @code{udev-configuration} object.")))

(define* (udev-service #:key (udev eudev) (rules '()))
  "Run @var{udev}, which populates the @file{/dev} directory dynamically.  Get
extra rules from the packages listed in @var{rules}."
  (service udev-service-type
           (udev-configuration (udev udev) (rules rules))))

(define* (udev-rules-service name rules #:key (groups '()))
  "Return a service that extends udev-service-type with RULES and
account-service-type with GROUPS as system groups.  This works by creating a
singleton service type NAME-udev-rules, of which the returned service is an
instance."
  (let* ((name (symbol-append name '-udev-rules))
         (account-extension
          (const (map (lambda (group)
                        (user-group (name group) (system? #t)))
                      groups)))
         (udev-extension (const (list rules)))
         (type (service-type
                (name name)
                (extensions (list
                             (service-extension
                              account-service-type account-extension)
                             (service-extension
                              udev-service-type udev-extension))))))
    (service type #f)))

(define (swap-space->shepherd-service-name space)
  (let ((target (swap-space-target space)))
    (symbol-append 'swap-
                   (string->symbol
                    (cond ((uuid? target)
                           (uuid->string target))
                          ((file-system-label? target)
                           (file-system-label->string target))
                          (else
                           target))))))

; TODO Remove after deprecation
(define (swap-deprecated->shepherd-service-name sdep)
  (symbol-append 'swap-
                 (string->symbol
                  (cond ((uuid? sdep)
                         (string-take (uuid->string sdep) 6))
                        ((file-system-label? sdep)
                         (file-system-label->string sdep))
                        (else
                         sdep)))))

(define swap->shepherd-service-name
  (match-lambda ((? swap-space? space)
                 (swap-space->shepherd-service-name space))
                (sdep
                 (swap-deprecated->shepherd-service-name sdep))))

(define swap-service-type
  (shepherd-service-type
   'swap
   (lambda (swap)
     (define requirements
       (cond ((swap-space? swap)
              (map dependency->shepherd-service-name
                   (swap-space-dependencies swap)))
             ; TODO Remove after deprecation
             ((and (string? swap) (string-prefix? "/dev/mapper/" swap))
              (list (symbol-append 'device-mapping-
                                   (string->symbol (basename swap)))))
             (else
              '())))

     (define device-lookup
       ;; The generic 'find-partition' procedures could return a partition
       ;; that's not swap space, but that's unlikely.
       (cond ((swap-space? swap)
              (let ((target (swap-space-target swap)))
                (cond ((uuid? target)
                       #~(find-partition-by-uuid #$(uuid-bytevector target)))
                      ((file-system-label? target)
                       #~(find-partition-by-label
                          #$(file-system-label->string target)))
                      (else
                       target))))
             ; TODO Remove after deprecation
             ((uuid? swap)
              #~(find-partition-by-uuid #$(uuid-bytevector swap)))
             ((file-system-label? swap)
              #~(find-partition-by-label
                 #$(file-system-label->string swap)))
             (else
              swap)))

     (with-imported-modules (source-module-closure '((gnu build file-systems)))
       (shepherd-service
        (provision (list (swap->shepherd-service-name swap)))
        (requirement `(udev ,@requirements))
        (documentation "Enable the given swap space.")
        (modules `((gnu build file-systems)
                   ,@%default-modules))
        (start #~(lambda ()
                   (let ((device #$device-lookup))
                     (and device
                          (begin
                            (restart-on-EINTR (swapon device
                                                      #$(if (swap-space? swap)
                                                            (swap-space->flags-bit-mask
                                                             swap)
                                                            0)))
                            #t)))))
        (stop #~(lambda _
                  (let ((device #$device-lookup))
                    (when device
                      (restart-on-EINTR (swapoff device)))
                    #f)))
        (respawn? #f))))
   (description "Turn on the virtual memory swap area.")))

(define (swap-service swap)
  "Return a service that uses @var{swap} as a swap space."
  (service swap-service-type swap))

(define %default-gpm-options
  ;; Default options for GPM.
  '("-m" "/dev/input/mice" "-t" "ps2"))

(define-record-type* <gpm-configuration>
  gpm-configuration make-gpm-configuration gpm-configuration?
  (gpm      gpm-configuration-gpm                 ;file-like
            (default gpm))
  (options  gpm-configuration-options             ;list of strings
            (default %default-gpm-options)))

(define gpm-shepherd-service
  (match-lambda
    (($ <gpm-configuration> gpm options)
     (list (shepherd-service
            (requirement '(udev))
            (provision '(gpm))
            ;; 'gpm' runs in the background and sets a PID file.
            ;; Note that it requires running as "root".
            (start #~(make-forkexec-constructor
                      (list #$(file-append gpm "/sbin/gpm")
                            #$@options)
                      #:pid-file "/var/run/gpm.pid"
                      #:pid-file-timeout 3))
            (stop #~(lambda (_)
                      ;; Return #f if successfully stopped.
                      (not (zero? (system* #$(file-append gpm "/sbin/gpm")
                                           "-k"))))))))))

(define gpm-service-type
  (service-type (name 'gpm)
                (extensions
                 (list (service-extension shepherd-root-service-type
                                          gpm-shepherd-service)))
                (default-value (gpm-configuration))
                (description
                 "Run GPM, the general-purpose mouse daemon, with the given
command-line options.  GPM allows users to use the mouse in the console,
notably to select, copy, and paste text.  The default options use the
@code{ps2} protocol, which works for both USB and PS/2 mice.")))


(define-record-type* <kmscon-configuration>
  kmscon-configuration     make-kmscon-configuration
  kmscon-configuration?
  (kmscon                  kmscon-configuration-kmscon
                           (default kmscon))
  (virtual-terminal        kmscon-configuration-virtual-terminal)
  (login-program           kmscon-configuration-login-program
                           (default (file-append shadow "/bin/login")))
  (login-arguments         kmscon-configuration-login-arguments
                           (default '("-p")))
  (auto-login              kmscon-configuration-auto-login
                           (default #f))
  (hardware-acceleration?  kmscon-configuration-hardware-acceleration?
                           (default #f))  ; #t causes failure
  (font-engine             kmscon-configuration-font-engine
                           (default "pango"))
  (font-size               kmscon-configuration-font-size
                           (default 12))
  (keyboard-layout         kmscon-configuration-keyboard-layout
                           (default #f))) ; #f | <keyboard-layout>

(define kmscon-service-type
  (shepherd-service-type
   'kmscon
   (lambda (config)
     (let ((kmscon (kmscon-configuration-kmscon config))
           (virtual-terminal (kmscon-configuration-virtual-terminal config))
           (login-program (kmscon-configuration-login-program config))
           (login-arguments (kmscon-configuration-login-arguments config))
           (auto-login (kmscon-configuration-auto-login config))
           (hardware-acceleration? (kmscon-configuration-hardware-acceleration? config))
           (font-engine (kmscon-configuration-font-engine config))
           (font-size (kmscon-configuration-font-size config))
           (keyboard-layout (kmscon-configuration-keyboard-layout config)))

       (define kmscon-command
         #~(list
            #$(file-append kmscon "/bin/kmscon") "--login"
            "--vt" #$virtual-terminal
            "--no-switchvt" ;Prevent a switch to the virtual terminal.
            "--font-engine" #$font-engine
            "--font-size" #$(number->string font-size)
            #$@(if keyboard-layout
                   (let* ((layout (keyboard-layout-name keyboard-layout))
                          (variant (keyboard-layout-variant keyboard-layout))
                          (model (keyboard-layout-model keyboard-layout))
                          (options (keyboard-layout-options keyboard-layout)))
                     `("--xkb-layout" ,layout
                       ,@(if variant `("--xkb-variant" ,variant) '())
                       ,@(if model `("--xkb-model" ,model) '())
                       ,@(if (null? options)
                             '()
                             `("--xkb-options" ,(string-join options ",")))))
                   '())
            #$@(if hardware-acceleration? '("--hwaccel") '())
            "--login" "--"
            #$login-program #$@login-arguments
            #$@(if auto-login
                   #~(#$auto-login)
                   #~())))

       (shepherd-service
        (documentation "kmscon virtual terminal")
        (requirement '(user-processes udev dbus-system))
        (provision (list (symbol-append 'term- (string->symbol virtual-terminal))))
        (start #~(make-forkexec-constructor #$kmscon-command))
        (stop #~(make-kill-destructor)))))
   (description "Start the @command{kmscon} virtual terminal emulator for the
Linux @dfn{kernel mode setting} (KMS).")))


;;;
;;; Static networking.
;;;

(define (ipv6-address? str)
  "Return true if STR denotes an IPv6 address."
  (false-if-exception (->bool (inet-pton AF_INET6 str))))

(define-compile-time-procedure (assert-valid-address (address string?))
  "Ensure ADDRESS has a valid netmask."
  (unless (cidr->netmask address)
    (raise
     (make-compound-condition
      (formatted-message (G_ "address '~a' lacks a network mask")
                         address)
      (condition (&error-location
                  (location
                   (source-properties->location procedure-call-location))))
      (condition (&fix-hint
                  (hint (format #f (G_ "\
Write, say, @samp{\"~a/24\"} for a 24-bit network mask.")
                                address)))))))
  address)

(define-record-type* <static-networking>
  static-networking make-static-networking
  static-networking?
  (addresses static-networking-addresses)         ;list of <network-address>
  (links     static-networking-links (default '())) ;list of <network-link>
  (routes    static-networking-routes (default '())) ;list of <network-routes>
  (provision static-networking-provision
             (default '(networking)))
  (requirement static-networking-requirement
               (default '(udev)))
  (name-servers static-networking-name-servers    ;FIXME: doesn't belong here
                (default '())))

(define-record-type* <network-address>
  network-address make-network-address
  network-address?
  (device    network-address-device)              ;string--e.g., "en01"
  (value     network-address-value                ;string--CIDR notation
             (sanitize assert-valid-address))
  (ipv6?     network-address-ipv6?                ;Boolean
             (thunked)
             (default
               (ipv6-address? (cidr->ip (network-address-value this-record))))))

(define-record-type* <network-link>
  network-link make-network-link
  network-link?
  (name      network-link-name)                   ;string--e.g, "v0p0"
  (type      network-link-type)                   ;symbol--e.g.,'veth
  (arguments network-link-arguments))             ;list

(define-record-type* <network-route>
  network-route make-network-route
  network-route?
  (destination network-route-destination)
  (source      network-route-source (default #f))
  (device      network-route-device (default #f))
  (ipv6?       network-route-ipv6? (thunked)
               (default
                 (or (ipv6-address? (network-route-destination this-record))
                     (and=> (network-route-gateway this-record)
                            ipv6-address?))))
  (gateway     network-route-gateway (default #f)))

(define* (cidr->netmask str #:optional (family AF_INET))
  "Given @var{str}, a string in CIDR notation (e.g., \"1.2.3.4/24\"), return
the netmask as a string like \"255.255.255.0\"."
  (match (string-split str #\/)
    ((ip (= string->number bits))
     (let ((mask (ash (- (expt 2 bits) 1)
                      (- (if (= family AF_INET6) 128 32)
                         bits))))
       (inet-ntop family mask)))
    (_ #f)))

(define (cidr->ip str)
  "Strip the netmask bit of @var{str}, a CIDR-notation IP/netmask address."
  (match (string-split str #\/)
    ((or (ip _) (ip))
     ip)))

(define* (ip+netmask->cidr ip netmask #:optional (family AF_INET))
  "Return the CIDR notation (a string) for @var{ip} and @var{netmask}, two
@var{family} address strings, where @var{family} is @code{AF_INET} or
@code{AF_INET6}."
  (let* ((netmask (inet-pton family netmask))
         (bits    (logcount netmask)))
    (string-append ip "/" (number->string bits))))

(define (static-networking->hurd-pfinet-options config)
  "Return command-line options for the Hurd's pfinet translator corresponding
to CONFIG."
  (unless (null? (static-networking-links config))
    ;; XXX: Presumably this is not supported, or perhaps could be approximated
    ;; by running separate pfinet instances in some cases?
    (warning (G_ "network links are currently ignored on GNU/Hurd~%")))

  (match (static-networking-addresses config)
    ((and addresses (first _ ...))
     `("--ipv6" "/servers/socket/26"
       "--interface" ,(network-address-device first)
       ,@(append-map (lambda (address)
                       `(,(if (network-address-ipv6? address)
                              "--address6"
                              "--address")
                         ,(cidr->ip (network-address-value address))
                         ,@(match (cidr->netmask (network-address-value address)
                                                 (if (network-address-ipv6? address)
                                                     AF_INET6
                                                     AF_INET))
                             (#f '())
                             (mask (list "--netmask" mask)))))
                     addresses)
       ,@(append-map (lambda (route)
                       (match route
                         (($ <network-route> "default" #f device _ gateway)
                          (if (network-route-ipv6? route)
                              `("--gateway6" ,gateway)
                              `("--gateway" ,gateway)))
                         (($ <network-route> destination)
                          (warning (G_ "ignoring network route for '~a'~%")
                                   destination)
                          '())))
                     (static-networking-routes config))))))

(define (network-set-up/hurd config)
  "Set up networking for the Hurd."
  ;; The Hurd implements SIOCGIFADDR and other old-style ioctls, but the only
  ;; way to set up IPv6 is by starting pfinet with the right options.
  (if (equal? (static-networking-provision config) '(loopback))
      (scheme-file "set-up-pflocal" #~(begin 'nothing-to-do! #t))
      (scheme-file "set-up-pfinet"
                   (with-imported-modules '((guix build utils))
                     #~(begin
                         (use-modules (guix build utils)
                                      (ice-9 format))

                         ;; TODO: Do that without forking.
                         (let ((options '#$(static-networking->hurd-pfinet-options
                                            config)))
                           (format #t "starting '~a~{ ~s~}'~%"
                                   #$(file-append hurd "/hurd/pfinet")
                                   options)
                           (apply invoke #$(file-append hurd "/bin/settrans") "-fac"
                                  "/servers/socket/2"
                                  #$(file-append hurd "/hurd/pfinet")
                                  options)))))))

(define (network-tear-down/hurd config)
  (scheme-file "tear-down-pfinet"
               (with-imported-modules '((guix build utils))
                 #~(begin
                     (use-modules (guix build utils))

                     ;; Forcefully terminate pfinet.  XXX: In theory this
                     ;; should just undo the addresses and routes of CONFIG;
                     ;; this could be done using ioctls like SIOCDELRT, but
                     ;; these are IPv4-only; another option would be to use
                     ;; fsysopts but that seems to crash pfinet.
                     (invoke #$(file-append hurd "/bin/settrans") "-fg"
                             "/servers/socket/2")
                     #f))))

(define network-set-up/linux
  (match-lambda
    (($ <static-networking> addresses links routes)
     (scheme-file "set-up-network"
                  (with-extensions (list guile-netlink)
                    #~(begin
                        (use-modules (ip addr) (ip link) (ip route))

                        #$@(map (lambda (address)
                                  #~(begin
                                      (addr-add #$(network-address-device address)
                                                #$(network-address-value address)
                                                #:ipv6?
                                                #$(network-address-ipv6? address))
                                      ;; FIXME: loopback?
                                      (link-set #$(network-address-device address)
                                                #:multicast-on #t
                                                #:up #t)))
                                addresses)
                        #$@(map (match-lambda
                                  (($ <network-link> name type arguments)
                                   #~(link-add #$name #$type
                                               #:type-args '#$arguments)))
                                links)
                        #$@(map (lambda (route)
                                  #~(route-add #$(network-route-destination route)
                                               #:device
                                               #$(network-route-device route)
                                               #:ipv6?
                                               #$(network-route-ipv6? route)
                                               #:via
                                               #$(network-route-gateway route)
                                               #:src
                                               #$(network-route-source route)))
                                routes)
                        #t))))))

(define network-tear-down/linux
  (match-lambda
    (($ <static-networking> addresses links routes)
     (scheme-file "tear-down-network"
                  (with-extensions (list guile-netlink)
                    #~(begin
                        (use-modules (ip addr) (ip link) (ip route)
                                     (netlink error)
                                     (srfi srfi-34))

                        (define-syntax-rule (false-if-netlink-error exp)
                          (guard (c ((netlink-error? c) #f))
                            exp))

                        ;; Wrap calls in 'false-if-netlink-error' so this
                        ;; script goes as far as possible undoing the effects
                        ;; of "set-up-network".

                        #$@(map (lambda (route)
                                  #~(false-if-netlink-error
                                     (route-del #$(network-route-destination route)
                                                #:device
                                                #$(network-route-device route)
                                                #:ipv6?
                                                #$(network-route-ipv6? route)
                                                #:via
                                                #$(network-route-gateway route)
                                                #:src
                                                #$(network-route-source route))))
                                routes)
                        #$@(map (match-lambda
                                  (($ <network-link> name type arguments)
                                   #~(false-if-netlink-error
                                      (link-del #$name))))
                                links)
                        #$@(map (lambda (address)
                                  #~(false-if-netlink-error
                                     (addr-del #$(network-address-device
                                                  address)
                                               #$(network-address-value address)
                                               #:ipv6?
                                               #$(network-address-ipv6? address))))
                                addresses)
                        #f))))))

(define (static-networking-shepherd-service config)
  (match config
    (($ <static-networking> addresses links routes
                            provision requirement name-servers)
     (let ((loopback? (and provision (memq 'loopback provision))))
       (shepherd-service

        (documentation
         "Bring up the networking interface using a static IP address.")
        (requirement requirement)
        (provision provision)

        (start #~(lambda _
                   ;; Return #t if successfully started.
                   (load #$(let-system (system target)
                             (if (string-contains (or target system) "-linux")
                                 (network-set-up/linux config)
                                 (network-set-up/hurd config))))))
        (stop #~(lambda _
                  ;; Return #f is successfully stopped.
                  (load #$(let-system (system target)
                            (if (string-contains (or target system) "-linux")
                                (network-tear-down/linux config)
                                (network-tear-down/hurd config))))))
        (respawn? #f))))))

(define (static-networking-shepherd-services networks)
  (map static-networking-shepherd-service networks))

(define (static-networking-etc-files interfaces)
  "Return a /etc/resolv.conf entry for INTERFACES or the empty list."
  (match (delete-duplicates
          (append-map static-networking-name-servers
                      interfaces))
    (()
     '())
    ((name-servers ...)
     (let ((content (string-join
                     (map (cut string-append "nameserver " <>)
                          name-servers)
                     "\n" 'suffix)))
       `(("resolv.conf"
          ,(plain-file "resolv.conf"
                       (string-append "\
# Generated by 'static-networking-service'.\n"
                                      content))))))))

(define static-networking-service-type
  ;; The service type for statically-defined network interfaces.
  (service-type (name 'static-networking)
                (extensions
                 (list
                  (service-extension shepherd-root-service-type
                                     static-networking-shepherd-services)
                  (service-extension etc-service-type
                                     static-networking-etc-files)))
                (compose concatenate)
                (extend append)
                (description
                 "Turn up the specified network interfaces upon startup,
with the given IP address, gateway, netmask, and so on.  The value for
services of this type is a list of @code{static-networking} objects, one per
network interface.")))

(define-deprecated (static-networking-service interface ip
                                              #:key
                                              netmask gateway provision
                                              ;; Most interfaces require udev to be usable.
                                              (requirement '(udev))
                                              (name-servers '()))
  static-networking-service-type
  "Return a service that starts @var{interface} with address @var{ip}.  If
@var{netmask} is true, use it as the network mask.  If @var{gateway} is true,
it must be a string specifying the default network gateway.

This procedure can be called several times, one for each network
interface of interest.  Behind the scenes what it does is extend
@code{static-networking-service-type} with additional network interfaces
to handle."
  (simple-service 'static-network-interface
                  static-networking-service-type
                  (list (static-networking
                         (addresses
                          (list (network-address
                                 (device interface)
                                 (value (if netmask
                                            (ip+netmask->cidr ip netmask)
                                            ip))
                                 (ipv6? #f))))
                         (routes
                          (if gateway
                              (list (network-route
                                     (destination "default")
                                     (gateway gateway)
                                     (ipv6? #f)))
                              '()))
                         (requirement requirement)
                         (provision (or provision '(networking)))
                         (name-servers name-servers)))))

(define %loopback-static-networking
  ;; The loopback device.
  (static-networking
   (addresses (list (network-address
                     (device "lo")
                     (value "127.0.0.1/8"))))
   (requirement '())
   (provision '(loopback))))

(define %qemu-static-networking
  ;; Networking configuration for QEMU's user-mode network stack (info "(QEMU)
  ;; Using the user mode network stack").
  (static-networking
   (addresses (list (network-address
                     (device "eth0")
                     (value "10.0.2.15/24"))))
   (routes (list (network-route
                  (destination "default")
                  (gateway "10.0.2.2"))))
   (requirement '())
   (provision '(networking))
   (name-servers '("10.0.2.3"))))


(define %base-services
  ;; Convenience variable holding the basic services.
  (list (service login-service-type)

        (service virtual-terminal-service-type)
        (service console-font-service-type
                 (map (lambda (tty)
                        (cons tty %default-console-font))
                      '("tty1" "tty2" "tty3" "tty4" "tty5" "tty6")))

        (syslog-service)
        (service agetty-service-type (agetty-configuration
                                       (extra-options '("-L")) ; no carrier detect
                                       (term "vt100")
                                       (tty #f) ; automatic
                                       (shepherd-requirement '(syslogd))))

        (service mingetty-service-type (mingetty-configuration
                                         (tty "tty1")))
        (service mingetty-service-type (mingetty-configuration
                                         (tty "tty2")))
        (service mingetty-service-type (mingetty-configuration
                                         (tty "tty3")))
        (service mingetty-service-type (mingetty-configuration
                                         (tty "tty4")))
        (service mingetty-service-type (mingetty-configuration
                                         (tty "tty5")))
        (service mingetty-service-type (mingetty-configuration
                                         (tty "tty6")))

        (service static-networking-service-type
                 (list %loopback-static-networking))
        (service urandom-seed-service-type)
        (service guix-service-type)
        (service nscd-service-type)

        (service rottlog-service-type)

        ;; The LVM2 rules are needed as soon as LVM2 or the device-mapper is
        ;; used, so enable them by default.  The FUSE and ALSA rules are
        ;; less critical, but handy.
        (service udev-service-type
                 (udev-configuration
                   (rules (list lvm2 fuse alsa-utils crda))))

        (service sysctl-service-type)

        (service special-files-service-type
                 `(("/bin/sh" ,(file-append bash "/bin/sh"))
                   ("/usr/bin/env" ,(file-append coreutils "/bin/env"))))))

;;; base.scm ends here