gnu: guix-configuration: Add a chroot? parameter.

The parameter should take the values #t, #f or 'default.
In a container environment, 'default amounts to #f, otherwise it
amounts to #t.

* gnu/services/base.scm (guix-configuration)<chroot?>: New field.
(guix-shepherd-service): If chroot? is #f, add "--disable-chroot".
If it is #t or 'default, do nothing.
* gnu/system/linux-container.scm (containerized-operating-system):
If chroot? is 'default, replace it by #f.
* doc/guix.texi: Document the parameter.

Change-Id: I8b9c3f46ad8650fa6ed4acee947b4ae5d002d03d

doc/guix.texi

@@ -19661,6 +19661,13 @@ Name of the group for build user accounts.
 @item @code{build-accounts} (default: @code{10})
 Number of build user accounts to create.
 
+@item @code{chroot?} (default: @code{'default})
+The value should be one of @code{#t} or @code{#f}, in which
+case chroot is enabled or disabled, respectively;
+or it should be @code{'default}, which amounts to @code{#f} in
+Docker containers (so that they can be run in non-privileged mode)
+or @code{#t} otherwise.
+
 @item @code{authorize-key?} (default: @code{#t})
 @cindex substitutes, authorization thereof
 Whether to authorize the substitute keys listed in

gnu/services/base.scm

@@ -21,6 +21,7 @@
 ;;; Copyright © 2022 Justin Veilleux <terramorpha@cock.li>
 ;;; Copyright © 2022 ( <paren@disroot.org>
 ;;; Copyright © 2023 Bruno Victal <mirai@makinata.eu>
+;;; Copyright © 2024 Andreas Enge <andreas@enge.fr>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -213,6 +214,7 @@
             guix-configuration-build-group
             guix-configuration-build-accounts
             guix-configuration-build-machines
+            guix-configuration-chroot?
             guix-configuration-authorize-key?
             guix-configuration-authorized-keys
             guix-configuration-use-substitutes?
@@ -1849,6 +1851,8 @@ archive' public keys, with GUIX."
                     (default "guixbuild"))
   (build-accounts   guix-configuration-build-accounts ;integer
                     (default 10))
+  (chroot?          guix-configuration-chroot? ;Boolean | 'default
+                    (default 'default))
   (authorize-key?   guix-configuration-authorize-key? ;Boolean
                     (default #t))
   (authorized-keys  guix-configuration-authorized-keys ;list of gexps
@@ -1943,7 +1947,7 @@ proxy of 'guix-daemon'...~%")
           glibc-utf8-locales)))
 
   (match-record config <guix-configuration>
-    (guix build-group build-accounts authorize-key? authorized-keys
+    (guix build-group build-accounts chroot? authorize-key? authorized-keys
           use-substitutes? substitute-urls max-silent-time timeout
           log-compression discover? extra-options log-file
           http-proxy tmpdir chroot-directories environment)
@@ -1990,6 +1994,9 @@ proxy of 'guix-daemon'...~%")
                           "--substitute-urls" #$(string-join substitute-urls)
                           #$@extra-options
 
+                          #$@(if chroot?
+                                 '()
+                                 '("--disable-chroot"))
                           ;; Add CHROOT-DIRECTORIES and all their dependencies
                           ;; (if these are store items) to the chroot.
                           (append-map

gnu/system/linux-container.scm

@@ -7,6 +7,7 @@
 ;;; Copyright © 2022 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2023 Pierre Langlois <pierre.langlois@gmx.com>
 ;;; Copyright © 2024 Leo Nikkilä <hello@lnikki.la>
+;;; Copyright © 2024 Andreas Enge <andreas@enge.fr>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -151,26 +152,28 @@ containerized OS.  EXTRA-FILE-SYSTEMS is a list of file systems to add to OS."
       (swap-devices '()) ; disable swap
       (services
        (append services-to-add
-               (filter-map (lambda (s)
-                             (cond ((memq (service-kind s) services-to-drop)
-                                    #f)
-                                   ((eq? nscd-service-type (service-kind s))
-                                    (service nscd-service-type
-                                             (nscd-configuration
-                                              (inherit (service-value s))
-                                              (caches %nscd-container-caches))))
-                                   ((eq? guix-service-type (service-kind s))
-                                    ;; Pass '--disable-chroot' so that
-                                    ;; guix-daemon can build thing even in
-                                    ;; Docker without '--privileged'.
-                                    (service guix-service-type
-                                             (guix-configuration
-                                              (inherit (service-value s))
-                                              (extra-options
-                                               (cons "--disable-chroot"
-                                                     (guix-configuration-extra-options
-                                                      (service-value s)))))))
-                                   (else s)))
+               (filter-map
+                 (lambda (s)
+                   (let ((kind (service-kind s))
+                         (value (service-value s)))
+                        (cond ((memq kind services-to-drop)
+                               #f)
+                              ((eq? nscd-service-type kind)
+                               (service nscd-service-type
+                                        (nscd-configuration
+                                         (inherit value)
+                                         (caches %nscd-container-caches))))
+                              ((and (eq? guix-service-type kind)
+                                    (eq? (guix-configuration-chroot? value)
+                                         'default))
+                               ;; If chroot? is 'default, it should become #f
+                               ;; so that guix-daemon can build things even in
+                               ;; Docker without '--privileged'.
+                               (service guix-service-type
+                                        (guix-configuration
+                                         (inherit value)
+                                         (chroot? #f))))
+                              (else s))))
                            (operating-system-user-services os))))
       (file-systems (append (map mapping->fs
                                  (if shared-network?