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[PATCH 5/7] docs/grub: document --emu-512b install option

From: Mihai Moldovan
Subject: [PATCH 5/7] docs/grub: document --emu-512b install option
Date: Sun, 24 May 2020 13:43:06 +0200

 docs/grub.texi | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/docs/grub.texi b/docs/grub.texi
index 1ce9993a5..f071487d6 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -6433,6 +6433,21 @@ validate the contents of the bootloader embedding area, 
or in more
 modern systems with GPT-style partition tables (@pxref{BIOS
 installation}) where GRUB does not reside in any unpartitioned space
 outside of the MBR.  Disable the Reed-Solomon codes with this option.
+@item --emu-512b
+By default on x86 BIOS systems, @command{grub-install} assumes a 512
+bytes sector size when generating and writing the core image. This
+option makes grub use the disk's native sector size for addressing the
+core image's blocks and a 512 bytes read block size, as often found
+with old/buggy system firmware. To that effect, the core image is
+spread out so that each read block starts on a proper hardware sector.
+Additionally, it enables read block and sector size autodetection in
+the @samp{biosdisk} access module by setting the
+@samp{biosdisk_autodetect_sector_size} variable to @samp{1}. You should
+@emph{only} use this option if you @emph{know} that your system
+firmware is buggy and can't handle disks with sector sizes bigger than
+512 bytes correctly and your machine is trying to boot off such a disk.
+It @emph{will} otherwise break normal operation.
 @end table
 @node Invoking grub-mkconfig

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