[syslinux] uefi and bios bootable optical media

Jur van der Burg jur at digiater.nl
Mon Feb 23 21:58:12 PST 2015

As I don't have much time right now I used grub2 to do the boot from dvd
via uefi. For the rest I use syslinux/extlinux.isolinux. Grub2 is a
nightmare to configure but in the end it does the job.

As sson as I've got more time I'll revisit iso9660 support for
efi in syslinux.


On 19-2-2015 0:06, Ady via Syslinux wrote:
>> We have been using syslinux (V4.05) in our product for years without a problem.
>> Since we encounter more and more systems that do a UEFI boot by default
>> we want to support that too. So I've been using syslinux V6.03 to create
>> usb sticks and harddisks to allow both bios and uefi boot which works fine.
>> The problem I run into now is that it is not possible to create a
>> dvd that is capable of booting in both ways. That is, I can create a
>> dvd, select a bootfile from efi but the boot itself fails. On vmware
>> the virtual machine powers off:
>> 5-02-17T11:35:21.009Z| vcpu-0| I120: Guest: About to do EFI boot: \efi\boot\bootx64.efi
>> 5-02-17T11:35:21.011Z| vcpu-0| I120: Msg_Post: Error
>> 5-02-17T11:35:21.011Z| vcpu-0| I120: [msg.efi.exception] The firmware encountered an unexpected exception. The virtual machine cannot boot.
>> If I specify another bootfile like shellx64.efi it will start, so
>> the process of creating the dvd and starting images is fine, the
>> issue is pure with syslinux. Bios boot from that dvd is fine fwiw.
>> Then I found this:
>>      http://www.syslinux.org/archives/2014-November/022780.html
>>   >For Syslinux (BIOS and EFI) in the .iso file:
>>   >_ the user might assume that the system can boot from optical media
>>   >not only in BIOS mode but also in UEFI mode (sadly, the latter is
>>   >currently untrue);
>> That looks to be my problem.
>>   >Realistically, less and less users are using optical media,
>>   >especially on newer computers (which are of course UEFI systems).
>>   >This means that investing resources in Syslinux development with the
>>   >specific goal of achieving bootable optical media in UEFI mode is
>>   >less "productive" than investing resources to achieve other
>>   >improvements / features. I'm not saying it won't happen - possibly by
>>   >adding some other, more-important features, then booting optical
>>   >media in UEFI mode might be also achievable.
>> Well, physical media are used less and less, I agree with that part.
>> On the other hand, a lot of installations on servers are done with
>> virtual media booting from a virtual dvd via an iso file, so it's
>> still used a lot.
>> So what can I do about this? Switch to grub? I really hate that
>> but if there's no alternative I may have to do that.
>> Or I may try to fix the issue myself. So is there anyone out there
>> that already knows a bit about this, and what the area is with the
>> pain? Or even if there's already been done some work to get it
>> to work?
>> Thanks,
>> Jur van der Burg.
> The problem is "simple": syslinux.efi v.6.03 can boot from the
> filesystems supported by SYSLINUX/EXTLINUX, and can network boot
> (similarly as PXELINUX), but currently it doesn't understand ISO9660
> (as ISOLINUX can).
> About what you could do, perhaps instead of using "iso images" in
> virtual environments, you could use network booting (similarly as
> PXELINUX for BIOS systems).
> About fixing the issue yourself, could you add support for ISO9660 in
> syslinux.efi? Patches are welcome!.
> Regards,
> Ady.
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