[PATCH v1 10/12] manual: add section about the images we released.

[Denis 'GNUtoo' Carikli]

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
---
 manual/gnuboot.texi | 117 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 114 insertions(+), 3 deletions(-)

diff --git a/manual/gnuboot.texi b/manual/gnuboot.texi
index e3612be..ccbf5b8 100644
--- a/manual/gnuboot.texi
+++ b/manual/gnuboot.texi
@@ -386,8 +386,8 @@ below.
 
 GNU Boot supports the GPUs that are present in the various laptops it
 supports with 100% free software. Some consideration apply while
-booting, but so far once booted these GPU are known to works well on
-tested computers.
+booting (see @pxref{GNU Boot images} for more details), but so far
+once booted these GPU are known to works well on tested computers.
 
 In addition for the non-laptop computers, it also supports the builtin
 AST graphics in the KGPE-D16 and KCMA-D8 with 100% free software, but
@@ -455,7 +455,9 @@ these and welcome contributions in this area.
 
 While GNU Boot should be able to boot almost any GNU/Linux
 distribution, but in some cases some configuration might be needed by
-the GNU Boot user.
+the GNU Boot user. The cases that do and don't require configuration
+from the user will be documented in the @pxref{GNU Boot images}
+section below.
 
 Even if some cases require some configuration, GNU Boot makes sure to
 provides at least one way to boot free GNU/Linux distributions (See
@@ -502,6 +504,115 @@ Also if you want to do such tests, you can open a bug 
report on the
 GNU Boot bug tracker at
 @url{https://savannah.gnu.org/bugs/?group=gnuboot}.
 
+@node GNU Boot images
+@section GNU Boot images
+
+In computers people are most familar with, like laptops, the @dfn{boot
+software} resides in a memory chip inside the mainboard (see
+@pxref{boot software} for more details).
+
+GNU Boot provide @dfn{images files} which are files that replace the
+content of these memory chip.
+
+These files are similar to
+@uref{https://en.wikipedia.org/wiki/Disk_image,disk images},
+@uref{https://en.wikipedia.org/wiki/ISO_image,ISO images}, or
+@uref{https://en.wikipedia.org/wiki/ROM_image,ROM images}.
+
+@node GNU Boot images types
+@subsection GNU Boot images types
+
+For a given computer, GNU Boot provides several images with different
+software in it. This enable the users to choose between:
+
+@itemize
+
+@item Two boot software: @dfn{GRUB} or @dfn{SeaBIOS (BIOS implementation)}
+
+@item Various keyboard layouts (@dfn{colemak}, @dfn{deqwertz}, @dfn{esqwerty},
+@dfn{frazerty}, @dfn{frdvbepo}, @dfn{itqwerty}, @dfn{svenska}, @dfn{trqwerty},
+@dfn{ukdvorak}, @dfn{ukqwerty}, @dfn{usdvorak}, @dfn{usqwerty}).
+
+@item Low resolution or high resolution graphics.
+
+@end itemize
+
+If you are a less technical user or helping one, or don't have much
+time to configure things, it is a good idea to choose an image with
+@dfn{GRUB}, and a keyboard layout of your choice (the resolution is
+not very important, but using high resolution looks nicer) as the
+image with @dfn{GRUB} doesn't require to do any configuration in the
+distributions you want to boot.
+
+Otherwise here are the advantages/disadvantages of each combinaison:
+
+@itemize
+
+@item @dfn{GRUB} with high resolution graphics: Images with GRUB
+usually don't require the user to do any configuration of the
+distribution. More technical users can also use that to customize
+the way the system boot for more security or to support unsual boot
+configurations (that are not typically supported by graphical installers
+of GNU/Linux distributions), however these more advanced configurations
+also come with their set of limitations.
+
+@item @dfn{SeaBIOS} with low text-only resolution: It implements
+BIOS compatibility, so it is very similar to a nonfree @dfn{BIOS} but
+it require users to modify some settings inside the distribution they
+use, otherwise the distribution still boots but usually has a black
+screen during the boot (which can be problematic to diagnose a
+non-booting distribution). The low resolution increase compatibility
+with various software that are typically run at boot like memtest86+
+(a software that detects broken RAM chips).
+
+@item @dfn{SeaBIOS} with high resolution and @dfn{GRUB} with low resolution:
+In most of the @dfn{images} provided by GNU Boot, it is possible to
+boot @dfn{GRUB} from @dfn{SeaBIOS} or vice-versa. So for instance
+@dfn{GRUB} with low-resolution can be interesting if you also want to
+boot with @dfn{SeaBIOS} in low resolution for increased compatibility.
+
+@end itemize
+
+@node GNU Boot images naming
+@subsection GNU Boot images naming
+
+Images for specific computers can be found on
+@uref{https://ftp.gnu.org/gnu/gnuboot/,the GNU Boot download area} or
+in the @dfn{release/roms} directory if you built GNU Boot from source
+yourself.
+
+For a given release (or release candidate) like GNU Boot 0.1-rc3, you
+can find such files inside the 'roms' directory like
+@url{https://ftp.gnu.org/gnu/gnuboot/gnuboot-0.1-rc3/roms/} for GNU
+Boot 0.1-rc3.
+
+Inside you have archive files like
+@option{gnuboot-0.1-rc3_x200_8mb.tar.xz} that are specific to a
+specific computer (here the ThinkPad X200 with 8MiB flash chip).
+
+Inside each archive files, there are many smaller files that are flash
+images. See the @pxref{boot software} section to understand what a
+@dfn{flash image} is.
+
+The flash image files correspond to the configurations described in
+the @pxref{GNU Boot images types} subsection.
+
+So for instance if we have an image named
+@option{grub_x200_8mb_corebootfb_usqwerty.rom}, it is meant for a
+ThinkPad X200 with 8MiB flash chip, and it uses the GRUB software to
+boot, and it is configured to use a QWERTY keyboard layout.
+
+If the image contains @option{seabios} in its file name instead of
+@option{grub}, it uses the SeaBIOS software to boot.
+
+The @option{corebootfb} in the file name correspond to the @dfn{high
+resolution graphics} described in the previous subsection (@pxref{GNU
+Boot images types}).
+
+If instead the file has @option{txtmode} in its name, this corresponds
+to the @dfn{low text-only resolution} that was also described in the
+previous subsection (@pxref{GNU Boot images types}).
+
 @node Helping GNU Boot
 @chapter Helping GNU Boot
 
-- 
2.46.0