[bug#41011] [PATCH] gnu: grub: Support for network boot via tftp/nfs.

[Stefan <stefan-guix@vodafonemail.de>]

* gnu/bootloader/grub.scm (grub-net-bootloader): New bootloader for
network booting via tftp.
(install-grub-net): New bootloader installer for tftp.
---
 gnu/bootloader/grub.scm | 79 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 75 insertions(+), 4 deletions(-)

diff --git a/gnu/bootloader/grub.scm b/gnu/bootloader/grub.scm
index b905ae360c..8f078dc2ac 100644
--- a/gnu/bootloader/grub.scm
+++ b/gnu/bootloader/grub.scm
@@ -24,7 +24,7 @@
 
 (define-module (gnu bootloader grub)
   #:use-module (guix records)
-  #:use-module ((guix utils) #:select (%current-system))
+  #:use-module ((guix utils) #:select (%current-system %current-target-system))
   #:use-module (guix gexp)
   #:use-module (gnu artwork)
   #:use-module (gnu bootloader)
@@ -46,8 +46,11 @@
             grub-theme-color-highlight
             grub-theme-gfxmode
 
+            install-grub-net
+
             grub-bootloader
             grub-efi-bootloader
+            grub-net-bootloader
             grub-mkrescue-bootloader
             grub-minimal-bootloader
 
@@ -501,11 +504,73 @@ fi~%"))))
                       "--bootloader-id=Guix"
                       "--efi-directory" target-esp))))
 
+(define (install-grub-net subdir)
+  "Define a grub-net bootloader installer for installation in SUBDIR,
+which is usually \"efi/boot\" or \"efi/Guix\"."
+  (let* ((arch (car (string-split (or (%current-target-system)
+                                      (%current-system))
+                                  #\-)))
+         (efi-bootloader-link (string-append "/boot"
+                                             (match arch
+                                               ("i686" "ia32")
+                                               ("x86_64" "x64")
+                                               ("arm" "arm")
+                                               ("armhf" "arm")
+                                               ("aarch64" "aa64")
+                                               ("riscv" "riscv32")
+                                               ("riscv64" "riscv64"))
+                                             ".efi"))
+         (efi-bootloader (string-append (match arch
+                                          ("i686" "i386")
+                                          ("x86_64" "x86_64")
+                                          ("arm" "arm")
+                                          ("armhf" "arm")
+                                          ("aarch64" "arm64")
+                                          ("riscv" "riscv32")
+                                          ("riscv64" "riscv64"))
+                                        "-efi/core.efi")))
+    #~(lambda (bootloader target mount-point)
+        "Install GRUB as e.g. \"bootx64.efi\" or \"bootarm64.efi\" \"into
+SUBDIR, which is usually \"efi/boot\" or \"efi/Guix\" below the directory TARGET
+for the system whose root is mounted at MOUNT-POINT."
+        (let* (;; Use target-depth and subdir-depth to construct links to
+               ;; "../gnu" and "../../../boot/grub/grub.cfg" with the correct
+               ;; number of "../". Note: This doesn't consider ".." or ".",
+               ;; which may appear inside target or subdir.
+               (target-depth (length (delete "" (string-split target #\/))))
+               (subdir-depth (length (delete "" (string-split #$subdir #\/))))
+               (up1 (string-join (make-list target-depth "..") "/" 'suffix))
+               (up2 (string-join (make-list subdir-depth "..") "/" 'suffix))
+               (net-dir (string-append mount-point target "/"))
+               (store-name (car (delete "" (string-split bootloader #\/))))
+               (store (string-append up1 store-name))
+               (store-link (string-append net-dir store-name))
+               (grub-cfg (string-append up1 up2 "boot/grub/grub.cfg"))
+               (grub-cfg-link (string-append net-dir #$subdir "/grub.cfg"))
+               (efi-bootloader-link
+                (string-append net-dir #$subdir #$efi-bootloader-link)))
+          ;; Tell 'grub-install' that there might be a LUKS-encrypted /boot or
+          ;; root partition.
+          (setenv "GRUB_ENABLE_CRYPTODISK" "y")
+          (invoke/quiet (string-append bootloader "/bin/grub-mknetdir")
+                        (string-append "--net-directory=" net-dir)
+                        (string-append "--subdir=" #$subdir))
+          (false-if-exception (delete-file store-link))
+          (symlink store store-link)
+          (false-if-exception (delete-file grub-cfg-link))
+          (symlink grub-cfg grub-cfg-link)
+          (false-if-exception (delete-file efi-bootloader-link))
+          (symlink #$efi-bootloader efi-bootloader-link)))))
+
 ^L
 
 ;;;
 ;;; Bootloader definitions.
 ;;;
+;;; For all these grub-bootloader variables the path to /boot/grub/grub.cfg
+;;; is fixed.  Inheriting and overwriting the field 'configuration-file' will
+;;; break 'guix system delete-generations', 'guix system switch-generation',
+;;; and 'guix system roll-back'.
 
 (define grub-bootloader
   (bootloader
@@ -516,12 +581,12 @@ fi~%"))))
    (configuration-file "/boot/grub/grub.cfg")
    (configuration-file-generator grub-configuration-file)))
 
-(define* grub-minimal-bootloader
+(define grub-minimal-bootloader
   (bootloader
    (inherit grub-bootloader)
    (package grub-minimal)))
 
-(define* grub-efi-bootloader
+(define grub-efi-bootloader
   (bootloader
    (inherit grub-bootloader)
    (installer install-grub-efi)
@@ -529,7 +594,13 @@ fi~%"))))
    (name 'grub-efi)
    (package grub-efi)))
 
-(define* grub-mkrescue-bootloader
+(define grub-net-bootloader
+  (bootloader
+   (inherit grub-efi-bootloader)
+   (name 'grub-net-bootloader)
+   (installer (install-grub-net "efi/Guix"))))
+
+(define grub-mkrescue-bootloader
   (bootloader
    (inherit grub-efi-bootloader)
    (package grub-hybrid)))
-- 
2.26.0