live-images: add details for GRUB on BIOS and GPT.

Closes: #428 [via git-merge-pr]

src/installation/live-images/guide.md

@@ -98,8 +98,8 @@ create a partition (typically between 200MB-1GB) of type `EFI System`, which
 will be mounted at `/boot/efi`.
 
 If using BIOS, it is recommended you select MBR for the partition table.
-Advanced users may use GPT but will need to create a special BIOS partition for
-`grub` to boot.
+Advanced users may use GPT but will need to [create a special BIOS
+partition](./partitions.md#bios-system-notes) for `grub` to boot.
 
 See the [Partitioning Notes](./partitions.md) for more details about
 partitioning your disk.

src/installation/live-images/partitions.md

@@ -19,9 +19,13 @@ The following sections will detail the options for partition configuration.
 ## BIOS system notes
 
 It is recommended that you create an MBR partition table if you are using a BIOS
-boot system. This will limit the number of partitions you create to four. It is
-possible to install a GPT partition table on a BIOS system, but grub will need a
-special partition to boot properly.
+boot system. This will limit the number of partitions you create to four.
+
+It is possible to use a GPT partition table on a BIOS system, but GRUB will
+require a special partition to boot properly. This partition should be at the
+beginning of your disk and have a size of 1MB, with type `BIOS boot` (GUID
+`21686148-6449-6E6F-744E-656564454649`). Don't create any filesystem in it. GRUB
+should then install itself successfully.
 
 ## UEFI system notes