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Re: Bug#821341: debian-installer: unbootable, no gpt partition for uefi install

Hi Steve,

thanks for your reply.

> It depends very much on the machine involved, to be honest - many will
> boot UEFI from appropriately partitioned MBR-partitioned disks. It
> depends very much on the firmware of the machine here.

hmmm...I didn't wade through the 1000+ page UEFI specs myself, but this
entry on superuser.com cites them and claims that according to the
specs, a UEFI boot partition /must/ reside on a gpt disk (this makes
some sense since gpt is part of the UEFI specs afaik...):


This MSDN article states the same

"Systems that support UEFI require that boot partition must reside on a
GPT disk. Other hard disks can be either MBR or GPT."

> This is clearly difficult to do in some cases, e.g. if
> other OSes are on the system already.

I agree that if somebody's installing to drive that already has
something installed on it, than you can't just go and change the mbr to
a gpt without asking. I was doing a virgin install of a new machine
originally partitioning and formatting a new blank disk. In this case
you should definitely have at least the option of having a gpt and
probably a notification that this would be preferable.

As far as I remember, I /did/ select expert install and I didn't find an
option for choosing gpt. Are you saying there is one, and I missed it?
If so, it doesn't seem easily findable (or I'm blind, or didn't select
expert install after all...).

If it is the case that the UEFI specs actually require a gpt for efi
boot, than a gpt should be the *default* for an UEFI install imho. If
d-i detects another OS and the disk is mbr, than d-i should display a
message either asking whether the disk should be converted to mbr
stating the risks and/or state that the system likely won't be UEFI
bootable if a gpt is not selected. All this should be available even in
a non-expert install, again imho.

Also, if it is the case that the UEFI specs require a gpt for efi boot,
and some systems are uefi booting from mbrs, than those are the buggy
ones, and whether one hopes it or not, one might expect that more and
more mainboard chipsets will implement the specs correctly and not uefi
boot from non-gpt disks. I have an MSI mainboard, which I think are
pretty good, and it definitely refused to boot from an mbr disk with an
efi partition.



On 18.04.2016 16:00, Steve McIntyre wrote:
> Control: merge -1 821340
> Control: reassign 821340 partman-efi
> Control: retitle 821340 partman-efi: add extra warning about preferring GPT for USE installation
> Hi Josh,
> I'm merging this with your other bug report - they're clearly the same
> issue.
> On Sun, Apr 17, 2016 at 10:37:53PM +0200, josh wrote:
>> Package: debian-installer
>> Severity: important
>> After installation system was not bootable.
>> During the installation it said that it had detected that I had UEFI
>> booted the installation CD and proposed to make an EFI boot partion
>> which I accepted. However, after installation, Debian wasn't bootable.
>> I tracked the problem down to the fact that even though it said it was
>> installing a UEFI bootable system, the hard drive was still partitioned
>> with an MBR, which is not UEFI boot compatible. There seemed to be no
>> option for selecting/forcing gpt partitioning.
>> Using a rescue cd and converting the MBR to a gpt and then reinstalling
>> grub-uefi solved the problem without having to reinstall the system.
>> It would seem to me that if the installer detects an uefi booted system
>> and is installing an efi boot partition then it should automatically
>> partition with a gpt and not an mbr.
> Again, it should be possible to do this (select GPT) using expert mode
> rather than having to restart. Maybe we should add a warning during
> partman-efi setup that some machines won't boot in MBR mode, and offer
> to switch. This is clearly difficult to do in some cases, e.g. if
> other OSes are on the system already.

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