[Bug 1879558] Re: grub-efi-amd64 postinst fails to install GRUB if previous GRUB install is not detected

[Daniel Richard G.]

> You can just run grub-install once by hand, and it will all update
correctly afterwards.

The package already has a good debconf-driven install process for GRUB
---requiring the user to do it manually not only discards the benefit of
that, it's a delicate and error-prone operation that most users are not
accustomed to doing (hence wrapping it in debconf).

The core of the problem is the chicken-and-egg scenario of requiring
GRUB to be installed in order to install GRUB. I just want to do e.g.
"dpkg-reconfigure grub-efi-amd64" on a newborn system, and have the
instalL_devices question come up. Right now, in order to get that, I
have to fool the postinst script by running "touch
/boot/grub/x86_64-efi/core.efi" beforehand. That's not a reasonable UI.

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https://bugs.launchpad.net/bugs/1879558

Title:
  grub-efi-amd64 postinst fails to install GRUB if previous GRUB install
  is not detected

Status in grub2 package in Ubuntu:
  Opinion

Bug description:
  This concerns grub-efi-amd64 2.04-1ubuntu26 in Ubuntu focal.

  Currently, when grub-efi-amd64 (or grub-efi-amd64-signed) is installed
  or reconfigured, the following steps occur:

    1. Package postinst script runs

    2. postinst checks if /boot/grub/x86_64-efi/core.efi is present, and
  if so...

    3. "/usr/lib/grub/grub-multi-install x86_64-efi" is invoked

  The check in #2 is accompanied by this comment:

          # Check /boot/grub to see if we previously installed to an ESP. We don't
          # want to trigger the install code just by installing the package,
          # normally the installer installs grub itself first.

  I very much *want* the package install (or configuration) to do the
  GRUB install, even if GRUB was not previously installed by the Ubuntu
  installer. I am specifically concerned with the case of a system with
  grub-pc being transitioned over to grub-efi-amd64. If a standard
  system image with the former is installed onto an EFI system, then
  this conversion is needed. (There is also the case of systems that are
  themselves converted from BIOS booting to EFI.)

  I do not know the motivation for the "only install if previously
  installed" check, but if the goal is to avoid installing GRUB to a
  plain /boot/efi/ directory (one that is not a separate special EFI
  partition), then it should be enough to check that /boot/efi/ is a
  mountpoint. I think it is reasonable to expect the user to set up the
  EFI partition and mount it prior to installing the package.

  (Ideally, the package would alert the user if it cannot install GRUB
  due to /boot/efi/ not being set up correctly.)

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