build, vm: Use a less common label.

* gnu/build/vm.scm (initialize-hard-disk): Use "GuixSD_image" as label.
* gnu/system/install.scm (installation-os): Likewise.
* gnu/system/vm.scm (system-disk-image): Likewise.

gnu/build/vm.scm

@@ -354,7 +354,7 @@ SYSTEM-DIRECTORY is the name of the directory of the 'system' derivation."
       (error "failed to create GRUB EFI image"))))
 
 (define* (make-iso9660-image grub config-file os-drv target
-                             #:key (volume-id "GuixSD") (volume-uuid #f))
+                             #:key (volume-id "GuixSD_image") (volume-uuid #f))
   "Given a GRUB package, creates an iso image as TARGET, using CONFIG-FILE as
 Grub configuration and OS-DRV as the stuff in it."
   (let ((grub-mkrescue (string-append grub "/bin/grub-mkrescue")))
@@ -440,11 +440,14 @@ passing it a directory name where it is mounted."
 
         ;; Create a tiny configuration file telling the embedded grub
         ;; where to load the real thing.
+        ;; XXX This is quite fragile, and can prevent the image from booting
+        ;; when there's more than one volume with this label present.
+        ;; Reproducible almost-UUIDs could reduce the risk (not eliminate it).
         (call-with-output-file grub-config
           (lambda (port)
             (format port
                     "insmod part_msdos~@
-                    search --set=root --label GuixSD~@
+                    search --set=root --label GuixSD_image~@
                     configfile /boot/grub/grub.cfg~%")))
 
         (display "creating EFI firmware image...")

gnu/system/install.scm

@@ -306,7 +306,7 @@ Use Alt-F2 for documentation.
      ;; the appropriate one.
      (cons* (file-system
               (mount-point "/")
-              (device "GuixSD")
+              (device "GuixSD_image")
               (title 'label)
               (type "ext4"))
 

gnu/system/vm.scm

@@ -345,7 +345,7 @@ to USB sticks meant to be read-only."
     ;; Volume name of the root file system.  Since we don't know which device
     ;; will hold it, we use the volume name to find it (using the UUID would
     ;; be even better, but somewhat less convenient.)
-    (normalize-label "GuixSD"))
+    (normalize-label "GuixSD_image"))
 
   (define file-systems-to-keep
     (remove (lambda (fs)