config/guix/system/usb-install-media: Fix build.

.config/guix/system/usb-install-media.scm

@@ -1,5 +1,5 @@
 ;; With Eshell:
-;; guix system -L .config/guix/system disk-image ~/.config/guix/system/usb-install-media.scm
+;; guix system -L ~/.config/guix/system disk-image ~/.config/guix/system/usb-install-media.scm
 
 (define-module (usb-install-media)
   #:use-module (default)
@@ -8,7 +8,7 @@
 (use-package-modules bootloaders)
 
 (operating-system
-  (inherit default-operating-system)
+  (inherit %ambrevar/default-os)
   ;; For some reason USB media can only be booted with GRUB set to "bios" mode.
   ;; It could have been possible to specialize default-operating-system
   ;; depending on (command-line) containing "reconfigure" or "disk-image", but
@@ -17,7 +17,7 @@
                (bootloader grub-bootloader)
                (target "/dev/sda")))
   (file-systems (cons* (file-system
-                         (device (file-system-label "guixsd"))
+                         (device (file-system-label "guix"))
                          (mount-point "/")
                          (type "ext4"))
                        (file-system