bug#24346: [PATCH] Generate grub.cfg with correct paths when store is not in root partition

[Carlos Sánchez de La Lama]

Rebasing to current master (76f31f0b), as new file-append made merge
non-trivial.

* guix/scripts/system.scm (previous-grub-entries): resolve initrd
  symlink for old entries (on the host).
* gnu/system.scm (operating-system-grub.cfg): resolve initrd symlink for
  current system (on the container).
* gnu/system/grub.scm: strip mount-point from GRUB filenames.

---
 gnu/system.scm          |  2 +-
 gnu/system/grub.scm     | 25 ++++++++++++++++++-------
 guix/scripts/system.scm |  6 +++---
 3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/gnu/system.scm b/gnu/system.scm
index 7edb018..281447f 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -738,7 +738,7 @@ listed in OS.  The C library expects to find it under
                                    #~(string-append "--load=" #$system
                                                     "/boot")
                                    (operating-system-kernel-arguments os)))
-                           (initrd (file-append system "/initrd"))))))
+                           (initrd #~(readlink #$(file-append system 
"/initrd")))))))
     (grub-configuration-file (operating-system-bootloader os)
                              store-fs entries
                              #:old-entries old-entries)))
diff --git a/gnu/system/grub.scm b/gnu/system/grub.scm
index 4592747..a00f568 100644
--- a/gnu/system/grub.scm
+++ b/gnu/system/grub.scm
@@ -62,6 +62,14 @@
 ;;;
 ;;; Code:
 
+(define (strip-mount-point fs file)
+  (let ((mount-point (file-system-mount-point fs)))
+    (if (string=? mount-point "/")
+       file
+       #~(if (string-prefix? #$mount-point #$file)
+             (substring #$file (string-length #$mount-point))
+             #$file))))
+
 (define-record-type* <grub-image>
   grub-image make-grub-image
   grub-image?
@@ -183,7 +191,8 @@ the store is.  SYSTEM must be the target system 
string---e.g.,
                      (symbol->string (assoc-ref colors 'bg)))))
 
   (define font-file
-    #~(string-append #$grub "/share/grub/unicode.pf2"))
+    (strip-mount-point root-fs
+                      #~(string-append #$grub "/share/grub/unicode.pf2")))
 
   (mlet* %store-monad ((image (grub-background-image config)))
     (return (and image
@@ -209,7 +218,7 @@ fi~%"
                            #$(grub-root-search root-fs font-file)
                            #$font-file
 
-                           #$image
+                           #$(strip-mount-point root-fs image)
                            #$(theme-colors grub-theme-color-normal)
                            #$(theme-colors grub-theme-color-highlight))))))
 
@@ -249,15 +258,17 @@ corresponding to old generations of the system."
   (define entry->gexp
     (match-lambda
      (($ <menu-entry> label linux arguments initrd)
-      #~(format port "menuentry ~s {
+      (let ((linux (strip-mount-point store-fs linux))
+            (initrd (strip-mount-point store-fs initrd)))
+        #~(format port "menuentry ~s {
   ~a
   linux ~a ~a
   initrd ~a
 }~%"
-                #$label
-                #$(grub-root-search store-fs linux)
-                #$linux (string-join (list address@hidden))
-                #$initrd))))
+                  #$label
+                  #$(grub-root-search store-fs linux)
+                  #$linux (string-join (list address@hidden))
+                  #$initrd)))))
 
   (mlet %store-monad ((sugar (eye-candy config store-fs system #~port)))
     (define builder
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index 953c624..5ff98a0 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -391,10 +391,10 @@ it atomically, and then run OS's activation script."
         (linux kernel)
         (linux-arguments
          (cons* (string-append "--root=" root-device)
-                #~(string-append "--system=" #$system)
-                #~(string-append "--load=" #$system "/boot")
+                (string-append "--system=" system)
+                (string-append "--load=" system "/boot")
                 kernel-arguments))
-        (initrd #~(string-append #$system "/initrd"))))))
+        (initrd (readlink (string-append system "/initrd")))))))
 
   (let* ((numbers (generation-numbers profile))
          (systems (map (cut generation-file-name profile <>)
-- 
2.9.2