[bug#29409] [PATCH] build: utils: Introduce dd.

[Mathieu Othacehe <m.othacehe@gmail.com>]

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> Granted, that’s a bit more verbose, but it’s also very lightweight
> compared to using ‘dd’.

Here's a new implementation, using your snippet. I tested it with
"installed-extlinux-os", it seems ok.

Mathieu

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From 742662ceec2a40d664520f01977ddc4cbe64d369 Mon Sep 17 00:00:00 2001
From: Mathieu Othacehe <m.othacehe@gmail.com>
Date: Fri, 1 Dec 2017 14:09:38 +0100
Subject: [PATCH] bootloader: extlinux: Stop using dd binary.

* gnu/bootloader/extlinux.scm (dd): Remove it,
(install-extlinux): replace dd call by Guile I/O procedures.
* gnu/system/vm.scm (qemu-image): Add (ice-9 binary-ports) to module-closure
and used-modules list to provide "get-bytevector-n" and "put-bytevector".
* guix/scripts/system.scm (bootloader-installer-derivation): Ditto.
---
 gnu/bootloader/extlinux.scm | 18 ++++++++----------
 gnu/system/vm.scm           |  6 ++++--
 guix/scripts/system.scm     |  6 ++++--
 3 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/gnu/bootloader/extlinux.scm b/gnu/bootloader/extlinux.scm
index 0db5598..98fad0c 100644
--- a/gnu/bootloader/extlinux.scm
+++ b/gnu/bootloader/extlinux.scm
@@ -85,14 +85,6 @@ TIMEOUT ~a~%"
 ;;; Install procedures.
 ;;;
 
-(define dd
-  #~(lambda (bs count if of)
-      (zero? (system* "dd"
-                      (string-append "bs=" (number->string bs))
-                      (string-append "count=" (number->string count))
-                      (string-append "if=" if)
-                      (string-append "of=" of)))))
-
 (define (install-extlinux mbr)
   #~(lambda (bootloader device mount-point)
       (let ((extlinux (string-append bootloader "/sbin/extlinux"))
@@ -102,8 +94,14 @@ TIMEOUT ~a~%"
                     (install-file file install-dir))
                   (find-files syslinux-dir "\\.c32$"))
 
-        (unless (and (zero? (system* extlinux "--install" install-dir))
-                     (#$dd 440 1 (string-append syslinux-dir "/" #$mbr) device))
+        (unless
+            (and (zero? (system* extlinux "--install" install-dir))
+                 (call-with-input-file (string-append syslinux-dir "/" #$mbr)
+                   (lambda (input)
+                     (let ((bv (get-bytevector-n input 440))
+                           (output (open-file device "wb0")))
+                       (put-bytevector output bv)
+                       (close-port output)))))
           (error "failed to install SYSLINUX")))))
 
 (define install-extlinux-mbr
diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
index b68cce3..b5fe786 100644
--- a/gnu/system/vm.scm
+++ b/gnu/system/vm.scm
@@ -274,11 +274,13 @@ the image."
   (expression->derivation-in-linux-vm
    name
    (with-imported-modules (source-module-closure '((gnu build vm)
-                                                   (guix build utils)))
+                                                   (guix build utils)
+                                                   (ice-9 binary-ports)))
      #~(begin
          (use-modules (gnu build vm)
                       (guix build utils)
-                      (srfi srfi-26))
+                      (srfi srfi-26)
+                      (ice-9 binary-ports))
 
          (let ((inputs
                 '#$(append (list qemu parted e2fsprogs dosfstools)
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index 91d151d..5116b82 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -674,9 +674,11 @@ any, are available.  Raise an error if they're not."
 and TARGET arguments."
   (with-monad %store-monad
     (gexp->file "bootloader-installer"
-                (with-imported-modules '((guix build utils))
+                (with-imported-modules '((guix build utils)
+                                         (ice-9 binary-ports))
                   #~(begin
-                      (use-modules (guix build utils))
+                      (use-modules (guix build utils)
+                                   (ice-9 binary-ports))
                       (#$installer #$bootloader #$device #$target))))))
 
 (define* (perform-action action os
-- 
2.7.4