Bug#919791: [grub-efi-amd64-bin] After upgrading grub-efi-amd64-signed GRUB was no longer bootable and I was thrown to UEFI settings

[Steve McIntyre]

On Sat, Jan 19, 2019 at 06:37:59PM +0200, Mikaela Suomalainen wrote:
>
>Today I installed updates normally, visited Windows 10 (slow ring)
>which offered only a Windows Defender definition update and rebooted
>to see that my GRUB was no longer functional. When Debian is the only
>enabled boot option in UEFI and I boot this laptop, I am thrown
>directly into UEFI setup.
>
>I didn't know what to do and wasn't willing to deal with GRUB, so I
>sought information about alternatives, found EFIStub on Debian Wiki,
>setup it following https://wiki.debian.org/EFIStub and booted my
>system using it. Then I went to #debian-next where three other people
>were also having trouble with grub, I was directed to #debian-boot
>where I was asked to report this.
>
>I selected this package as the bug target as this is the only package
>I have upgraded according to `grep grub /var/log/dpkg.log|grep
>2019-01-19`.
>
>This device is ASUS X550JX.

Hi Mikaela,

This is worrying behaviour, definitely. Updating Windows should *not*
be affecting your system in this way, clearly. I'm not 100% sure, but
what you're describing sounds like it *could* be a problem with UEFI
Secure Boot. We don't (quite) have Secure Boot working in Debian, so
you would have had to disable it to get Debian working in the first
place.

Has the Windows update somehow re-enabled Secure Boot? Could you check
in yor firmware/BIOS settings please?

-- 
Steve McIntyre, Cambridge, UK.                                steve at einval.com
"This dress doesn't reverse." -- Alden Spiess