From 9f3b9ebfdcebcfc9d202a9e2aa155278c83776f0 Mon Sep 17 00:00:00 2001
From: Thierry Vignaud <thierry.vignaud@gmail.com>
Date: Thu, 22 Nov 2018 04:21:11 +0100
Subject: doc: explain how to support a bootloader

---
 perl-install/bootloader.pm | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

(limited to 'perl-install/bootloader.pm')

diff --git a/perl-install/bootloader.pm b/perl-install/bootloader.pm
index 215e70f42..71d50eaa6 100644
--- a/perl-install/bootloader.pm
+++ b/perl-install/bootloader.pm
@@ -33,6 +33,50 @@ Example of usage:
     (...)
     bootloader::action($bootloader, 'write', $all_hds);
 
+A particular bootloader is handled in separate typical functions that can be called by action() by /sbin/bootloader-config:
+
+
+=head1 VFS aka how to support a bootloader
+
+Most of the code is generic.
+
+A particular bootloader implementation/support is done through a couple functions:
+
+=over 4
+
+=item * read_FOOBAR()
+
+read the config file(s) of the FOOBAR bootloader, returning a $bootloader object
+
+=item * install_FOOBAR($bootloader, $all_hds)
+
+usually call write_FOOBAR() & install_raw_FOOBAR() if existing, aka:
+
+=over 4
+
+=item * updating config files
+
+=item * then reinstalling the bootloader
+
+=back
+
+=item * install_raw_FOOBAR()
+
+Optionnal: Low level installation of the stage1 of the bootloader, usually embedding it in MBR or on ESP, ... (eg: running lilo or /boot/grub*/install.sh)
+
+=item * write_FOOBAR($bootloader, $all_hds)
+
+update the config files, ie when a kernel was installed or removed.
+when_config_changed_FOOBAR() is called right after in case something is needed when config is done (eg: lilo needs to be reinstalled)
+
+=item * when_config_changed_FOOBAR()
+
+Run needed action when config has changed or when initrds were regenerated, ...
+Usually nothing for intelligent bootloaders such as grub-legacy or grub2.
+But eg: lilo needs to rewrite its stage1 (thus it needs to rerun lilo).
+
+=back
+
 =head1 Functions
 
 =over
@@ -2419,6 +2463,8 @@ Calls the C<$action> function with @para parameters:
 
 If needed, the function name will be resolved to call a boot loader specific function (eg: for LILO/GRUB/...)
 
+This Swiss army knife function is heavily used by eg /sbin/bootloader-config
+
 =cut
 
 sub action {
-- 
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