Re: How to boot a 32-bit Ubuntu on a 64-bit EFI machine?

[Ulf Zibis]

Am 16.09.21 um 23:34 schrieb Ulf Zibis:
> Am 16.09.21 um 18:55 schrieb Andrei Borzenkov:
> > The only similar error message in upstream grub is
> > "kernel does not support 64-bit addressing"
>
> Thanks!
>
> I now additionally have installed Ubuntu-64 16.04.1 without connection to the 
> internet, to prevent from installing a newer GRUB version than from the install 
> ISO medium.
>
> So now I have grub-efi-and64 in version 2.02~beta2-36ubuntu3.1 to boot with.
>
> With this version I'm able to boot Ubuntu-32 18.04.1 and Ubuntu-32 16.04.7 with 
> a very recent kernel.

So, I've become a little smarter now ...

On the Ubuntu 16.04.1 install media the packages grub-efi-amd64* are in version 
2.02~beta2-36ubuntu3.1.

With this *all 32-bit versions* (16.04.1, 16.04.7_ESM, 18.04.1 and 18.04.6) of 
Ubuntu *can be started perfectly*.

But if I want at least the last security update (without "optional" updates) 
from xenial-security (and stay at 2.02*), I have to establish an Internet connection in 
the live system.

Then I get version 2.02~beta2-36ubuntu3.27.
With that *GRUB gets stuck with a blank screen* when trying to start a 32-bit Ubuntu. (In 
one case also with "loading initial RAM disk ...".)

On the Ubuntu 18.04.4 install media the packages grub-efi-amd64* are in version 
2.02-2ubuntu8.14.
*All 32-bit versions* of Ubuntu *can also be started* with this.

And with an established internet connection I get: 2.04-1ubuntu44.1.2.
With that *GRUB then gets stuck**with "kernel doesn't support 64-bit CPUs"* 
when trying to start a 32-bit Ubuntu.

How it behaves with Ubuntu 18.06.4 or even Ubuntu 20.04.1, I have not tested.

> So I still suspect, that the reason for my problem is the kernel version.

I also have scanned the sources of the Ubuntu flavour of GRUB and did not find a message 
matching to "kernel doesn't support 64-bit CPUs".

So your assumption, that this message is generated by the kernel, seems 
probable. The miracle is, why older versions of GRUB do not trigger it, but 
newer versions do.

-Ulf