system: Add (gnu system accounts).

The (gnu system accounts) module is meant to be used both on the build-
and on the host-side.

* gnu/system/shadow.scm <top level>: Call 'default-shell'.
(<user-account>, <user-group>): Move to...
* gnu/system/accounts.scm: ... here.  New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add system/accounts.scm.

3 files changed, 109 insertions, 49 deletions

diff --git a/gnu/local.mk b/gnu/local.mk
index 29fb31bf2d..d6d9209830 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -532,6 +532,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/services/xorg.scm				\
 						\
   %D%/system.scm				\
+  %D%/system/accounts.scm			\
   %D%/system/file-systems.scm			\
   %D%/system/install.scm			\
   %D%/system/linux-container.scm		\
diff --git a/gnu/system/accounts.scm b/gnu/system/accounts.scm
new file mode 100644
index 0000000000..36ee62e851
--- /dev/null
+++ b/gnu/system/accounts.scm
@@ -0,0 +1,81 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; 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 system accounts)
+  #:use-module (guix records)
+  #:export (user-account
+            user-account?
+            user-account-name
+            user-account-password
+            user-account-uid
+            user-account-group
+            user-account-supplementary-groups
+            user-account-comment
+            user-account-home-directory
+            user-account-create-home-directory?
+            user-account-shell
+            user-account-system?
+
+            user-group
+            user-group?
+            user-group-name
+            user-group-password
+            user-group-id
+            user-group-system?
+
+            default-shell))
+
+
+;;; Commentary:
+;;;
+;;; Data structures representing user accounts and user groups.  This is meant
+;;; to be used both on the host side and at run time--e.g., in activation
+;;; snippets.
+;;;
+;;; Code:
+
+(define default-shell
+  ;; Default shell for user accounts (a string or string-valued gexp).
+  (make-parameter "/bin/sh"))
+
+(define-record-type* <user-account>
+  user-account make-user-account
+  user-account?
+  (name           user-account-name)
+  (password       user-account-password (default #f))
+  (uid            user-account-uid (default #f))
+  (group          user-account-group)             ; number | string
+  (supplementary-groups user-account-supplementary-groups
+                        (default '()))            ; list of strings
+  (comment        user-account-comment (default ""))
+  (home-directory user-account-home-directory)
+  (create-home-directory? user-account-create-home-directory? ;Boolean
+                          (default #t))
+  (shell          user-account-shell              ; gexp
+                  (default (default-shell)))
+  (system?        user-account-system?            ; Boolean
+                  (default #f)))
+
+(define-record-type* <user-group>
+  user-group make-user-group
+  user-group?
+  (name           user-group-name)
+  (password       user-group-password (default #f))
+  (id             user-group-id (default #f))
+  (system?        user-group-system?              ; Boolean
+                  (default #f)))
diff --git a/gnu/system/shadow.scm b/gnu/system/shadow.scm
index 63f544cec9..a9a4afd414 100644
--- a/gnu/system/shadow.scm
+++ b/gnu/system/shadow.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016 Alex Griffin <a@ajgrf.com>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -24,6 +24,7 @@
   #:use-module (guix modules)
   #:use-module (guix sets)
   #:use-module (guix ui)
+  #:use-module (gnu system accounts)
   #:use-module (gnu services)
   #:use-module (gnu services shepherd)
   #:use-module ((gnu system file-systems)
@@ -36,27 +37,29 @@
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-35)
-  #:export (user-account
-            user-account?
-            user-account-name
-            user-account-password
-            user-account-uid
-            user-account-group
-            user-account-supplementary-groups
-            user-account-comment
-            user-account-home-directory
-            user-account-create-home-directory?
-            user-account-shell
-            user-account-system?
-
-            user-group
-            user-group?
-            user-group-name
-            user-group-password
-            user-group-id
-            user-group-system?
-
-            default-skeletons
+
+  ;; Re-export these bindings for backward compatibility.
+  #:re-export (user-account
+               user-account?
+               user-account-name
+               user-account-password
+               user-account-uid
+               user-account-group
+               user-account-supplementary-groups
+               user-account-comment
+               user-account-home-directory
+               user-account-create-home-directory?
+               user-account-shell
+               user-account-system?
+
+               user-group
+               user-group?
+               user-group-name
+               user-group-password
+               user-group-id
+               user-group-system?)
+
+  #:export (default-skeletons
             skeleton-directory
             %base-groups
             %base-user-accounts
@@ -70,33 +73,8 @@
 ;;;
 ;;; Code:
 
-(define-record-type* <user-account>
-  user-account make-user-account
-  user-account?
-  (name           user-account-name)
-  (password       user-account-password (default #f))
-  (uid            user-account-uid (default #f))
-  (group          user-account-group)             ; number | string
-  (supplementary-groups user-account-supplementary-groups
-                        (default '()))            ; list of strings
-  (comment        user-account-comment (default ""))
-  (home-directory user-account-home-directory)
-  (create-home-directory? user-account-create-home-directory? ;Boolean
-                          (default #t))
-  (shell          user-account-shell              ; gexp
-                  (default (file-append bash "/bin/bash")))
-  (system?        user-account-system?            ; Boolean
-                  (default #f)))
-
-(define-record-type* <user-group>
-  user-group make-user-group
-  user-group?
-  (name           user-group-name)
-  (password       user-group-password (default #f))
-  (id             user-group-id (default #f))
-  (system?        user-group-system?              ; Boolean
-                  (default #f)))
-
+;; Change the default shell used by new <user-account> records.
+(default-shell (file-append bash "/bin/bash"))
 
 (define %base-groups
   ;; Default set of groups.