3.7 Appendix: clean up the discussion of SYSLINUX for legacy boot mode

crux-wiki/Handbook3-7-Appendix

@@ -101,30 +101,31 @@ the newer GPT (GUID) partition table is supported by
 partition table looks like. An identification of the exact partition type (DOS
 or GPT) will appear next to ''Disklabel type:'' in the fdisk output.
 
--> Also inspect the @@fdisk -l@@ output to make sure that the boot flag is
-enabled on the partition where you save %fn%ldlinux.c32%% in the commands
-below. This partition must be flagged as bootable in order for the binary
-blob to proceed with loading the syslinux code.
-
 Once you determine the binary blob that will work with your partition table, run
 the commands that will copy that binary blob into the master boot record.
-'''Remember to replace ''sda'' with your actual device.'''
+'''Remember to replace ''sda'' with your actual device. The first command sets
+''INSTALLDIR'' as the path to a directory on a vfat or ext2/3/4 filesystem
+('''which must be flagged as bootable in the partition table'''). In this
+example we use a path that minimizes the hassle when toggling your BIOS between
+UEFI and legacy boot methods. A less confusing option is commented out, for
+BIOSes that truly have no UEFI capability.'''
 
+ $ INSTALLDIR=/boot/efi/EFI/BOOT       # or /boot/syslinux
  $ PTYPE=$(fdisk -l /dev/sda | grep "^Disklabel type" | cut -d " " -f3)
  $ [ "$PTYPE" = "gpt" ] && BINBLOB=gptmbr.bin || BINBLOB=mbr.bin
- $ mkdir -p /boot/efi/BOOT
- $ cd /boot/efi/BOOT
+ $ mkdir -p $INSTALLDIR
+ $ cd $INSTALLDIR
  $ cp /usr/share/syslinux/ldlinux.c32 .
- $ extlinux --install /boot/efi/BOOT/
+ $ extlinux --install $INSTALLDIR
  $ dd bs=440 count=1 conv=notrunc if=/usr/share/syslinux/$BINBLOB of=/dev/sda
  $ vi syslinux.cfg
 
--> The @@extlinux@@ command takes a ''directory of the mounted EFI system
-partition'' as its argument, rather than a device node. Upstream documentation
-begins with an example of calling the @@syslinux@@ command with the ''device
-node'' as its argument, which assumes that the EFI system partition is not
-mounted. Because you're already creating files on this partition, we demonstrate
-the command that won't require you to unmount the partition before running it.
+-> The @@extlinux@@ command takes a ''directory under a mounted partition'' as
+its argument, rather than a device node. Upstream documentation begins with an
+example of calling the @@syslinux@@ command with the ''device node'' as its
+argument, which assumes that the partition is not mounted. Because you're
+already creating files on this partition, we demonstrate the command that won't
+require you to unmount the partition before running it.
 The @@extlinux@@ command is also smart enough to set its argument (the ''install
 target'') as the directory to be searched for configuration files, so you can
 proceed to launch the editor on %fn%syslinux.cfg%% (see the next section for a
@@ -148,12 +149,10 @@ label CRUX-3.7
 @]
 
 When giving the location of a kernel image, relative paths are interpreted in
-reference to the %fn%syslinux.cfg%% file. In the example above, where
-@@extlinux@@ assigned %fn%/boot/efi/BOOT/%% as the preferred location for
+reference to the %fn%syslinux.cfg%% file. In the example above, if
+@@extlinux@@ assigned %fn%/boot/efi/EFI/BOOT/%% as the preferred location for
 %fn%syslinux.cfg%%, the kernel would have to be copied to
-%fn%/boot/efi/BOOT/vmlinuz-5.15.55%%. Saving kernels here (in the BOOT
-subdirectory of the EFI system partition) is a common practice when using the
-kernel itself as a bootloader; see the next section for more details.
+%fn%/boot/efi/EFI/BOOT/vmlinuz-5.15.55%%.
 
 [[#EFI-stub-install]]
 !! EFI Stub installation notes
@@ -186,7 +185,7 @@ you leave the boot options empty during kernel configuration, and the BIOS does
 not honor your appended options, you might have to boot from a rescue disk to
 get back into your system and fix things.
 
-* Copy your built kernel to the BOOT subdirectory of the EFI system partition
+* Copy your built kernel to a subdirectory of the EFI system partition
 (mounted at %fn%/boot/efi%%). For maximum compatibility, save it with the
 extension %fn%.efi%%.