[Bug 1898022] Re: grub upgrade 18.04->20.04 loses dual-boot to W10

[udippel]

I have three identical helix 2. They all came with Windows preinstalled.
And I could add 18.04 LTS without problem, including getting the grub
boot menu presented without any further action. Only with a later LTS
update did it disappear. So to me this is a regression. I don't want to
indulge into a discussion if it is a necessary or unnecessary
regression. To me, personally, it is disappointing.

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR='Kubuntu'
GRUB_CMDLINE_LINUX_DEFAULT='quiet splash resume=UUID=b2e084d0-2cce-4cad-ba48-ed13be62e0b0'
GRUB_CMDLINE_LINUX=""

$ sudo update-grub
Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-6.8.0-45-generic
Found initrd image: /boot/initrd.img-6.8.0-45-generic
Found linux image: /boot/vmlinuz-6.8.0-41-generic
Found initrd image: /boot/initrd.img-6.8.0-41-generic
Found memtest86+ 64bit EFI image: /memtest86+x64.efi
Warning: os-prober will be executed to detect other bootable partitions.
Its output will be used to detect bootable binaries on them and create new boot entries.
Found Windows Boot Manager on /dev/sda2@/EFI/Microsoft/Boot/bootmgfw.efi
Adding boot menu entry for UEFI Firmware Settings ...
done


** Attachment added: "grub.cfg as requested"
   https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1898022/+attachment/5823695/+files/grub.cfg

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https://bugs.launchpad.net/bugs/1898022

Title:
  grub upgrade 18.04->20.04 loses dual-boot to W10

Status in grub2 package in Ubuntu:
  Incomplete

Bug description:
  (Summary says it:)

  Upgraded by dual-boot kubuntu 18.04 to kubuntu 20.04. After the restart, dual-boot was gone, and it boots directly into kubuntu. 
  I guess it is a problem with grub, because the boot menu doesn't show. However, the 'lenovo' shows trice, while it used to show once with 18.04; followed by the grub boot menu. 

  I guess that the MBR was written into haywire?

  ProblemType: Bug
  DistroRelease: Ubuntu 20.04
  Package: grub-efi-amd64-bin 2.04-1ubuntu26.4
  ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
  Uname: Linux 5.4.0-48-generic x86_64
  ApportVersion: 2.20.11-0ubuntu27.9
  Architecture: amd64
  CasperMD5CheckResult: skip
  CurrentDesktop: KDE
  Date: Thu Oct  1 11:34:39 2020
  InstallationDate: Installed on 2019-03-14 (566 days ago)
  InstallationMedia: Kubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
  SourcePackage: grub2
  UpgradeStatus: Upgraded to focal on 2020-09-29 (1 days ago)

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