Syslinux - Aug 2019 - Getting classic BIOS and UEFI boot on the same disk?

I just created something very similar for one of my own projects. I have a
disk image that you can "dd" onto a hard drive or USB drive and a bash
script demonstrating how it was done here:

https://www.syslinux.org/archives/2019-July/026476.html

You don't actually need the patch for the dual BIOS/UEFI support. The patch
in the above link is just to enable the reading of config "snippits"
from a
"entries" directory. Feel free to try out the provided disk image to
see if
it meets your needs and reverse-engineer the bash script to suit your needs.


On Wed, Aug 21, 2019 at 1:34 PM William R. Somsky via Syslinux <
syslinux at syslinux.org> wrote:
>
> I'm not sure if it is useful, but with the advent of UEFI only
machines,
> we've run into a similar problem w/ out custom CentOS 7 USB
installation
> keys.
>
> Basically, we create a gpt device w/ a single FAT16 partition (this
> would be your /boot partition for a full installation) containing an
> EFI/BOOT/ directory with the syslinux-efi files and a SYSLINUX/
> directory with the syslinux-bios files.
>
> Would further info on this be helpful?
>
> - WRSomsky
>
>
> On Wed, Aug 21, 2019 at 12:57:05PM +0200, Erik Rull via Syslinux wrote:
> > Hi all,
> >
> > We're using the classic boot BIOS syslinux successfully for many
years,
> but
> > meanwhile it's getting harder to buy hardware the still supports
this
> boot
> > mode.
> > The option for us would be syslinux EFI boot.
> > To avoid too many changes we would like to generate an image for our
> different
> > hardware parts that supports both - classic BIOS boot and (U)EFI boot.
> > This would allow us to leave the BIOS in whatever state it is and the
> system
> > will simply boot.
> >
> > [[...]]
>
> --
> Dr. William R. Somsky                                      somsky at uw.edu
> Department of Physics, Box 351560                   B217 Phys-Astro Bldg
> Univ. of Washington, Seattle WA 98195-1560                  206-616-2954
> _______________________________________________
> Syslinux mailing list
> Submissions to Syslinux at syslinux.org
> Unsubscribe or set options at:
> https://lists.syslinux.org/syslinux
>

Hello Greg,

thanks a lot - I will try out your script next week.
I jut went through the script - there is a line containing:
bls1 include

I would carefully assume that this line is only valid when patching syslinux,
correct? What will happen if this is read by a non-patched syslinux? Will it
cause errors or will it simply be ignored?

Best regards,

Erik


Gregory Bartholomew wrote:
> I just created something very similar for one of my own projects. I have a
disk
> image that you can "dd" onto a hard drive or USB drive and a bash
script
> demonstrating how it was done here:
> 
> https://www.syslinux.org/archives/2019-July/026476.html
> 
> You don't actually need the patch for the dual BIOS/UEFI support. The
patch in
> the above link is just to enable the reading of config "snippits"
from a
> "entries" directory. Feel free to try out the provided disk image
to see if it
> meets your needs and reverse-engineer the bash script to suit your needs.
> 
> 
> On Wed, Aug 21, 2019 at 1:34 PM William R. Somsky via Syslinux
> <syslinux at syslinux.org <mailto:syslinux at syslinux.org>>
wrote:
> 
> 
>     I'm not sure if it is useful, but with the advent of UEFI only
machines,
>     we've run into a similar problem w/ out custom CentOS 7 USB
installation
>     keys.
> 
>     Basically, we create a gpt device w/ a single FAT16 partition (this
>     would be your /boot partition for a full installation) containing an
>     EFI/BOOT/ directory with the syslinux-efi files and a SYSLINUX/
>     directory with the syslinux-bios files.
> 
>     Would further info on this be helpful?
> 
>     - WRSomsky
> 
> 
>     On Wed, Aug 21, 2019 at 12:57:05PM +0200, Erik Rull via Syslinux wrote:
>     > Hi all,
>     >
>     > We're using the classic boot BIOS syslinux successfully for
many years, but
>     > meanwhile it's getting harder to buy hardware the still
supports this boot
>     > mode.
>     > The option for us would be syslinux EFI boot.
>     > To avoid too many changes we would like to generate an image for
our different
>     > hardware parts that supports both - classic BIOS boot and (U)EFI
boot.
>     > This would allow us to leave the BIOS in whatever state it is and
the system
>     > will simply boot.
>     >
>     > [[...]]
> 
>     -- 
>     Dr. William R. Somsky? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? somsky at
uw.edu
>     <mailto:somsky at uw.edu>
>     Department of Physics, Box 351560? ? ? ? ? ? ? ? ? ?B217 Phys-Astro
Bldg
>     Univ. of Washington, Seattle WA 98195-1560? ? ? ? ? ? ? ? ?
206-616-2954
>     _______________________________________________
>     Syslinux mailing list
>     Submissions to Syslinux at syslinux.org <mailto:Syslinux at
syslinux.org>
>     Unsubscribe or set options at:
>     https://lists.syslinux.org/syslinux
>

On Fri, Aug 30, 2019 at 12:15 PM Erik Rull <erik.rull at rdsoftware.de>
wrote:
> Hello Greg,
>
> thanks a lot - I will try out your script next week.
> I jut went through the script - there is a line containing:
> bls1 include
>
> I would carefully assume that this line is only valid when patching
> syslinux,
> correct? What will happen if this is read by a non-patched syslinux? Will
> it
> cause errors or will it simply be ignored?
>
>
That is correct. "bls1 include" would cause errors without the patch.
The
main parts of the script that would be relevant to you would be the parts
that create the partition, set its type codes, write the first-stage boot
loader to the first 440 bytes of the disk, and lay out the file system
(e.g. it demonstrates that a single /syslinux.cfg file can be shared
between both the UEFI and BIOS binaries). Much of the rest of it would be
irrelevant for your case.