[Bug 1684341] [grub2/xenial] possible regression found

[Ubuntu Foundations Team Bug Bot]

As a part of the Stable Release Updates quality process a search for
Launchpad bug reports using the version of grub2 from xenial-proposed
was performed and bug 1692181 was found.  Please investigate this bug
report to ensure that a regression will not be created by this SRU. In
the event that this is not a regression remove the "verification-failed"
tag from this bug report and add the tag "bot-stop-nagging" to bug
1692181 (not this bug). Thanks!

** Tags added: verification-failed

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https://bugs.launchpad.net/bugs/1684341

Title:
  EFI fallback binary should not be installed in --removable mode

Status in cloud-images:
  New
Status in grub2 package in Ubuntu:
  Fix Released
Status in grub2 source package in Trusty:
  Confirmed
Status in grub2 source package in Xenial:
  Fix Committed
Status in grub2 source package in Yakkety:
  Confirmed
Status in grub2 source package in Zesty:
  In Progress

Bug description:
  [Impact]
  Building some images depending on calling grub-install --removable still installs fbx64.efi; which we don't want on removable media.

  [Test case]
  On an EFI system, run 'grub-install --removable --target=x86_64-efi'. Observe whether fbx64.efi is installed to /boot/efi/EFI/BOOT. It should not.

  [Regression potential]
  If any system is depending on running grub-install with --removable, and on fbx64.efi being installed in /boot/efi/EFI/BOOT; this would cause this assumption to fail -- leading to incorrect fallback behavior when BootEntries are not present on a system.

  Failures to boot with "System BootOrder not found" errors should be
  considered a possible regression.

  Any missing files in /boot/efi/EFI/BOOT or /boot/efi/EFI/ubuntu after
  install should be considered a potential regression of this update.

  
  ----

  
  The patch I did to fix names for the new naming of shim binaries included the addition of fbx64.efi; but it was done wrong: fbx64.efi should only exist under \EFI\BOOT, it's not required in the "removable" path; except if we're trying to force installing to the removable path *too*.

  In other words:
  1) we normally don't want /EFI/ubuntu/fbx64.efi to exist;

  and
  a) on a desktop or server, we want /EFI/BOOT/fbx64.efi to exist (ie. installs without --removable, and with --force-extra-removable used when grub-install was called);
  b) on removable media, we do not want /EFI/BOOT/fbx64.efi to exist (ie. when grub-installed is called with --removable).

  Furthermore, the (a) case is probably not the typical case we want to
  run grub-install with. Calls to grub-install with --force-extra-
  removable probably should be limited to shim-signed's postinst.

  In any case, let's move the fbx64.efi installation step to
  also_install_removable() in grub-installer to avoid installing it when
  it shouldn't be.

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