[syslinux] What's the best way to get Syslinux to boot efi?

[David Juhl]

What is top posting? And thanks for the help.

On Fri, Aug 19, 2016, 8:08 PM Ady Ady via Syslinux <syslinux at zytor.com>
wrote:

>
> > Sorry thinking about this problem at work, I'm using my cellphone. Won't
> > get home until 1am.
> >
> > I run Gentoo.
> > https://wiki.gentoo.org/wiki/Syslinux#Setup_on_EFI_systems
> >
> > is my distribution instructions on installing Syslinux.
> >
> > http://www.syslinux.org/wiki/index.php?title=Install#UEFI
> > are your instructions.
> >
> > I have tried both instructions only to get a blank or black screen.
> >
> > Trying to make a bootable usb that will boot with efi so I can run
> > efibootmgr.
> >
> > Just wondering which is correct, or should I uninstall gentoo's Syslinux,
> > download it and compile it, and follow your website's instructions. Not
> > having much luck in their forums.
>
>
> The instructions in the respective wiki pages are not conflicting each
> other; you just need to read them carefully.
>
> The instructions in Gentoo's wiki suggest mounting the "EFI System
> Partition" on a specific path ("/boot/efi"), and then it is suggested
> to create a (sub)directory on it.
>
> If your OS (Gentoo) on which you are executing the instructions is
> already booted in UEFI mode, the (sub)directory that is being suggested
> is "EFI/syslinux/". That is:
>
>  <root_of_the_ESP>/EFI/systlinux/
>
> Since the root of the ESP was mounted as "/boot/efi", then the path at
> this time in your OS is seen as:
>
>  /boot/efi/EFI/syslinux/
>
> Later in the instructions, this new (sub)directory ("EFI/syslinux/") is
> used in the 'efibootmgr' command (with backslash "\", instead of slash
> "/"). ---> The "efibootmgr" command is the problematic instruction for
> this case!
>
> The instructions referring to the 'efibootmgr' command in this specific
> Gentoo wiki page are not for a different (USB) removable device, but
> rather for adding "syslinux.efi" as an alternative UEFI bootloader for
> the _same_ ESP of the current OS in which you are executing the
> command. To be clear, I am not saying that the specific efibootmgr
> command in this specific Gentoo wiki page is correct or incorrect, but
> rather that, as-is, it is not intended for installing syslinux.efi on a
> _different_ (removable, USB device) ESP.
>
> The same Gentoo wiki page suggests an alternative: use the "default"
> (as per the UEFI specifications) (sub)directory for your syslinux.efi,
> and this is where it matches the instructions of the Syslinux wiki.
>
> The "default" (sub)directory is:
>
>  <root_of_the_ESP>/EFI/BOOT/
>
> In this case, the "root_of_the_ESP" is not the one in your current OS /
> device, but the ESP in your USB device. Additionally, Gentoo's wiki
> page uses "Boot" instead of "BOOT" (all upper-case). Strictly speaking,
> the UEFI specifications uses "BOOT"; I am not sure whether this small
> inaccuracy in Gentoo's wiki page has a practical negative effect in
> real-world cases.
>
> In line with using the "default" UEFI directory as alternative method,
> also the default name for the UEFI bootloader is suggested in Gentoo's
> wiki page. For the "x86_64" architecture, this is "bootx64.efi", and
> again this coincides with Syslinux's wiki page. The result for this
> particular case is:
>
>  <root_of_the_ESP_in_the_USB_device>/EFI/BOOT/BOOTX64.EFI
>
> or, as it is expressed in the Syslinux wiki page:
>
>  EFI_SYSTEM_PARTITION/EFI/BOOT/BOOTX64.EFI
>
> (please note that in the Syslinux wiki page the "EFI_SYSTEM_PARTITION"
> is in italics).
>
> As explained in both wiki pages, the rest of the Syslinux-related files
> should be copied to the same location. That means that your
> "syslinux.cfg", "ldlinux.e64", and any required c32 module for the same
> "efi64" architecture should be copied to the same location (including
> lib*.c32):
>
>  <root_of_the_ESP_in_the_USB_device>/EFI/BOOT/
>
> Now, with the instructions (hopefully) being clarified, there are
> additional things to be noted. First, UEFI implementations are not
> "perfect". For instance, some UEFI firmware might use a different
> default path, such as "EFI/Microsoft/Bootmgr.efi" or simuilar, instead
> of the default path according to the UEFI specs. This is just one
> example, and many other issues can be found in real-world cases. There
> isn't much that The Syslinux Project can do about it.
>
> Additionally, the Syslinux wiki pages should not be expected to explain
> "anything and everything about booting", whether it would be regarding
> traditional PC-BIOS or regarding UEFI.
>
> Moreover, bugs and potential improvements in syslinux.efi are a
> certainty (and this includes building issues). It would be useful for
> the The Syslinux Project to know if there is a system that is
> UEFI-bootable by means of a different bootloader but fails to boot with
> syslinux.efi.
>
> Please also note that Syslinux configuration examples are usually
> focused on BIOS systems. For UEFI, it is very possible that the paths
> expressed in your own syslinux.cfg might need some tweaking; such as
> changing things like "/boot/" to "/EFI/BOOT/" or similar.
>
> Regards,
> Ady.
>
> PS: When replying, please avoid top-posting. TIA.
>
>
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