system: reconfigure: Use the disk-installer if provided.

Fixes: <https://issues.guix.gnu.org/44101>.

* gnu/build/bootloader.scm (write-file-on-device): Pass 'no-fail flag instead
of 'no-create. Use a latin-1 transcoder.
* guix/scripts/system/reconfigure.scm (install-bootloader-program): Add a
"disk-installer" argument and use it as a fallback.
(install-bootloader): Adapt accordingly.
* gnu/tests/reconfigure.scm (run-install-bootloader-test): Ditto.

3 files changed, 22 insertions, 6 deletions

diff --git a/gnu/build/bootloader.scm b/gnu/build/bootloader.scm
index 5ec839f902..3916930c89 100644
--- a/gnu/build/bootloader.scm
+++ b/gnu/build/bootloader.scm
@@ -38,10 +38,13 @@
     (lambda (input)
       (let ((bv (get-bytevector-n input size)))
         (call-with-port
+         ;; Do not use "call-with-output-file" that would truncate the file.
          (open-file-output-port device
-                                (file-options no-truncate no-create)
+                                (file-options no-truncate no-fail)
                                 (buffer-mode block)
-                                (native-transcoder))
+                                ;; Use the binary-friendly ISO-8859-1
+                                ;; encoding.
+                                (make-transcoder (latin-1-codec)))
          (lambda (output)
            (seek output offset SEEK_SET)
            (put-bytevector output bv)))))))
diff --git a/gnu/tests/reconfigure.scm b/gnu/tests/reconfigure.scm
index 928a210a94..52beeef447 100644
--- a/gnu/tests/reconfigure.scm
+++ b/gnu/tests/reconfigure.scm
@@ -260,7 +260,9 @@ bootloader's configuration file."
      ;; test suite, the bootloader installer script is omitted. 'grub-install'
      ;; would attempt to write directly to the virtual disk if the
      ;; installation script were run.
-     (test (install-bootloader-program #f #f bootcfg bootcfg-file #f "/")))))
+     (test
+      (install-bootloader-program #f #f #f bootcfg bootcfg-file #f "/")))))
+
 
 (define %test-switch-to-system
   (system-test
diff --git a/guix/scripts/system/reconfigure.scm b/guix/scripts/system/reconfigure.scm
index d89caf80fc..5581e12892 100644
--- a/guix/scripts/system/reconfigure.scm
+++ b/guix/scripts/system/reconfigure.scm
@@ -204,7 +204,8 @@ services as defined by OS."
 ;;; Bootloader configuration.
 ;;;
 
-(define (install-bootloader-program installer bootloader-package bootcfg
+(define (install-bootloader-program installer disk-installer
+                                    bootloader-package bootcfg
                                     bootcfg-file device target)
   "Return an executable store item that, upon being evaluated, will install
 BOOTCFG to BOOTCFG-FILE, a target file name, on DEVICE, a file system device,
@@ -246,10 +247,17 @@ BOOTLOADER-PACKAGE."
              ;; a broken installation.
              (switch-symlinks new-gc-root #$bootcfg)
              (install-boot-config #$bootcfg #$bootcfg-file #$target)
-             (when #$installer
+             (when (or #$installer #$disk-installer)
                (catch #t
                  (lambda ()
-                   (#$installer #$bootloader-package #$device #$target))
+                   ;; The bootloader might not support installation on a
+                   ;; mounted directory using the BOOTLOADER-INSTALLER
+                   ;; procedure. In that case, fallback to installing the
+                   ;; bootloader directly on DEVICE using the
+                   ;; BOOTLOADER-DISK-IMAGE-INSTALLER procedure.
+                   (if #$installer
+                       (#$installer #$bootloader-package #$device #$target)
+                       (#$disk-installer #$bootloader-package 0 #$device)))
                  (lambda args
                    (delete-file new-gc-root)
                    (match args
@@ -272,11 +280,14 @@ additional configurations specified by MENU-ENTRIES can be selected."
   (let* ((bootloader (bootloader-configuration-bootloader configuration))
          (installer (and run-installer?
                          (bootloader-installer bootloader)))
+         (disk-installer (and run-installer?
+                              (bootloader-disk-image-installer bootloader)))
          (package (bootloader-package bootloader))
          (device (bootloader-configuration-target configuration))
          (bootcfg-file (bootloader-configuration-file bootloader)))
     (eval #~(parameterize ((current-warning-port (%make-void-port "w")))
               (primitive-load #$(install-bootloader-program installer
+                                                            disk-installer
                                                             package
                                                             bootcfg
                                                             bootcfg-file