32 bit UEFI

Steve Langasek steve.langasek at ubuntu.com
Wed Jan 8 00:04:05 UTC 2014

Hi Phillip,

On Mon, Dec 30, 2013 at 02:02:07PM -0500, Phillip Susi wrote:
> It seems that the number of pure 32 bit UEFI systems is growing and so
> we can't continue to ignore them.  The reason that we don't support
> UEFI on 32 bit images now is that some older systems have broken
> biosen that blow up when the el torito boot catalog contains multiple
> entries, and we don't want to have to maintain and test two separate
> images.

> What if we transition the main 32 bit image to UEFI support, and to
> support those few people that still have very aged systems that don't
> deal with it, we could have a non UEFI flavor of only the netinst
> image?  That should have minimal overhead to maintain.

This is one of those compatibility requirements about which we have little
data, to tell us when we should make the switch from maximal BIOS
compatibility to UEFI compatibility.  (Just like knowing when to switch from
32-bit by default to 64-bit by default, only worse.)

At this point, I imagine that the newest 32-bit machines that don't handle
El Torito multicatalog correctly are about a decade old; the oldest are
probably much older.  I suspect there aren't many of them left around that
are targets for new Ubuntu installs (or reinstalls).  In contrast, we know
that there are an awful lot of new UEFI-only 32-bit x86 machines being
manufactured (to my general surprise), and that users are going to want to
run Ubuntu on these.

Colin, do you recall any details of specific BIOS versions known to have
problems with El Torito multiboot?

FWIW, if we did add UEFI multiboot to i386 ISOs, we probably wouldn't
actually do a netinst as a fallback for BIOS compatibility - 'netinst' being
a Debian image type that we don't generate at all today for Ubuntu, and
which would certainly require independent QA in an Ubuntu context.  There
would be the mini.iso from
which is basically just a netboot image in ISO form; people could use that
if they wished, in an unsupported capacity.  But frankly, I expect that any
machines which are incapable of handling El Torito multiboot are equally
incapable of running Unity.  So if we were making this decision on a
per-flavor basis, I would be in favor of dropping broken-BIOS compatibility
and adding UEFI compatibility to our Ubuntu i386 ISOs.

Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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