system: Make /boot/grub/grub.cfg an indirect GC root.

Fixes <http://bugs.gnu.org/19160>.

* guix/scripts/system.scm (install-grub*): Make /boot/grub/grub.cfg an
  indirect GC root.
* gnu/build/install.scm (install-grub): Make TARGET a symlink.
* gnu/build/vm.scm (register-grub.cfg-root): New procedure.
  (initialize-hard-disk): Use it.

1 files changed, 16 insertions, 0 deletions

diff --git a/gnu/build/vm.scm b/gnu/build/vm.scm
index 03db1cd5f9..1762582343 100644
--- a/gnu/build/vm.scm
+++ b/gnu/build/vm.scm
@@ -178,6 +178,18 @@ volume name."
   (display "populating...\n")
   (populate-root-file-system system-directory target-directory))
 
+(define (register-grub.cfg-root target)
+  "On file system TARGET, make '/boot/grub/grub.cfg' an indirect GC root."
+  (define hash
+    ;; XXX: Believe it or not, this is that nix-base32-encoded SHA1 of the
+    ;; string "/boot/grub/grub.cfg".  We need it here, but gcrypt isn't
+    ;; available (a random hash would do as well, though.)
+    "kv0yq1d48kavqfhjfzvc4lcyazx2mqhv")
+
+  (let ((directory (string-append target "/var/guix/gcroots/auto")))
+    (mkdir-p directory)
+    (symlink "/boot/grub/grub.cfg" (string-append directory "/" hash))))
+
 (define* (initialize-hard-disk device
                                #:key
                                system-directory
@@ -222,6 +234,10 @@ SYSTEM-DIRECTORY is the name of the directory of the 'system' derivation."
 
   (install-grub grub.cfg device target-directory)
 
+  ;; Register $target/boot/grub/grub.cfg as an indirect root, so that GRUB.CFG
+  ;; is not reclaimed.
+  (register-grub.cfg-root target-directory)
+
   ;; 'guix-register' resets timestamps and everything, so no need to do it
   ;; once more in that case.
   (unless register-closures?