system: Don't make /boot/grub/grub.cfg a symlink to the store.

This would not work when /boot is a separate partition, as reported by
Nikita Karetnikov <nikita@karetnikov.org> in <http://bugs.gnu.org/19220>.
This fixes a regression introduced in 39d1f82.

* gnu/build/install.scm (install-grub): Copy GRUB.CFG instead of
  symlinking it, as was the case before 39d1f82.
* gnu/build/vm.scm (register-grub.cfg-root): Add 'grub.cfg' parameter.
  Make it a permanent GC root instead of an indirect GC root.
  (initialize-hard-disk): Adjust accordingly.
* guix/scripts/system.scm (install-grub*): Replace use of
  'add-indirect-root' by the addition of a permanent GC root in
  %GC-ROOTS-DIRECTORY.

1 files changed, 8 insertions, 5 deletions

diff --git a/gnu/build/install.scm b/gnu/build/install.scm
index 111b79ee59..aa901f6971 100644
--- a/gnu/build/install.scm
+++ b/gnu/build/install.scm
@@ -36,15 +36,18 @@
 
 (define* (install-grub grub.cfg device mount-point)
   "Install GRUB with GRUB.CFG on DEVICE, which is assumed to be mounted on
-MOUNT-POINT.  Note that the caller must make sure that GRUB.CFG is registered
-as a GC root."
+MOUNT-POINT.
+
+Note that the caller must make sure that GRUB.CFG is registered as a GC root
+so that the fonts, background images, etc. referred to by GRUB.CFG are not
+GC'd."
   (let* ((target (string-append mount-point "/boot/grub/grub.cfg"))
          (pivot  (string-append target ".new")))
     (mkdir-p (dirname target))
 
-    ;; Symlink GRUB.CFG, under the assumption that it has been registered as a
-    ;; GC root somewhere.  Do that atomically.
-    (symlink grub.cfg pivot)
+    ;; Copy GRUB.CFG instead of just symlinking it, because symlinks won't
+    ;; work when /boot is on a separate partition.  Do that atomically.
+    (copy-file grub.cfg pivot)
     (rename-file pivot target)
 
     (unless (zero? (system* "grub-install" "--no-floppy"