doc: Improve UEFI/BIOS bootloader documentation.

Partly fixes <https://bugs.gnu.org/30312>.

* doc/guix.texi (Preparing for Installation): Add note on how to choose
between UEFI and BIOS.
(Using the Configuration System)[Bootloader]: New subsubsection.
(Bootloader Configuration): Expound on the bootloader type and target.
* gnu/system/examples/desktop.tmpl: Switch to UEFI.
* gnu/system/examples/bare-bones.tmpl: Explicitly mention "legacy" and
"BIOS" in the comments.

1 files changed, 3 insertions, 2 deletions

diff --git a/gnu/system/examples/bare-bones.tmpl b/gnu/system/examples/bare-bones.tmpl
index cb6d2623db9..b763258e524 100644
--- a/gnu/system/examples/bare-bones.tmpl
+++ b/gnu/system/examples/bare-bones.tmpl
@@ -10,8 +10,9 @@
   (timezone "Europe/Berlin")
   (locale "en_US.utf8")
 
-  ;; Assuming /dev/sdX is the target hard disk, and "my-root" is
-  ;; the label of the target root file system.
+  ;; Boot in "legacy" BIOS mode, assuming /dev/sdX is the
+  ;; target hard disk, and "my-root" is the label of the target
+  ;; root file system.
   (bootloader (bootloader-configuration
                 (bootloader grub-bootloader)
                 (target "/dev/sdX")))