[syslinux] Changes to get CD to boot on EFI System.

Ady ady-sf at hotmail.com
Sat Apr 2 00:49:49 PDT 2016

> Hi,
> H. Peter Anvin wrote:
> > Look for a "legacy boot" option; otherwise you need the CD-ROM to have
> > the EFI version of Syslinux or another bootloader on it
> The "another bootloader" is clear to me.
> But what are the prescriptions for preparing a SYSLINUX EFI System
> Partition that boots out of a CD ?
> (Those built according to
>    http://www.syslinux.org/wiki/index.php?title=Install#UEFI
>  are known not to be able to do this.)
The "Install" wiki page does not include information about booting 
optical media in UEFI mode by means of any Syslinux variant at this 
point. This status might change in the future, if some Syslinux variant 
gets such capacity.

> Do you know examples (ready ISOs or production software for ISOs)
> which use SYSLINUX for EFI together with ISOLINUX and do not
> have to contain a full-fledged operating system in the ESP ?
> Have a nice day :)
> Thomas
I certainly do not know of any published ISO image that is capable of 
booting optical media in UEFI mode and that the main bootloader for 
such capability is part of the Syslinux family.

Furthermore, I very much doubt that there is any ISO image, publicly 
available or not, that can boot optical media in UEFI mode by means of 
Syslinux for EFI as of today. I hope this status will change at some 

I also doubt that Peter has ever tested this feature. This is my guess, 
not a fact I know about, but I think that, if Peter would had ever 
tested this supposed capability, he would not be insinuating anything 
near such statement.

More guesses: I think there is no active developer related to The 
Syslinux Project that has built ISO images for quite some time, except 
for Thomas attempting to test (and trying to support users). I have 
built ISO images, but I am not a developer and I certainly do not claim 
that Syslinux for EFI is capable of booting optical media in UEFI mode 
in any way at this point.

BTW, I doubt that syslinux.efi (renamed as "EFI/BOOT/BOOT<arch>.EFI") 
is capable of booting optical media in UEFI mode at this point, whether 
with the whole full-fledged OS embedded within the FAT image (popularly 
known as "efiboot.img"), or even with no OS at all (i.e. just getting 
to the syslinux.efi boot prompt and nothing else, not even a cfg file). 
I will be glad to be proven wrong.

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