[Bug 1642298] Re: Grub package upgrades overwrites NVRAM, causing MAAS boot order to be overwritten.

[Blake Rouse]

I think this is more of a GRUB issue overall instead of a MAAS issue
directly. True it affects MAAS and we can do the debconf selections to
work around this issue but overall for quality of Ubuntu I do not
believe this is the proper fix.

I will give an example without MAAS.

1. First the user installs Ubuntu on a partition on their local disk, EFI is updated so Ubuntu can boot.
2. Second the user installs Windows on another partition. EFI is updates so Windows can boot and its first.
3. User reboots into Ubuntu, runs apt-get, and grub updates changing the boot order so now that Ubuntu boots first.
4. User reboots their machine and Ubuntu boots but the user expected Windows to boot.

Overall this is a bad experience to the user.

I think the grub code should be smart about this:

First check if the grub.efi loader already exists in efibootmgr. If it
does not exists add it to the loader and set it to boot first. If it
does exist record its current place in the boot order, update the loader
and reset the boot order to its previous location.

That change would fix this for any user that uses Ubuntu as well as MAAS
users.

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https://bugs.launchpad.net/bugs/1642298

Title:
  Grub package upgrades overwrites NVRAM, causing MAAS boot order to be
  overwritten.

Status in curtin:
  Confirmed
Status in MAAS:
  Confirmed
Status in grub2 package in Ubuntu:
  Fix Released
Status in grub2 source package in Trusty:
  Triaged
Status in grub2 source package in Xenial:
  Triaged
Status in grub2 source package in Yakkety:
  Triaged

Bug description:
  [Impact]
  Typically when you install Ubuntu on an EFI system, it installs a new default EFI boot entry that makes the system reboot directly into the OS. During MAAS installs, curtin is careful to disable that behavior. MAAS requires the default boot entry to remain PXE, so that it can direct the system to boot from disk or network as necessary. curtin does this by passing --no-nvram to grub-install when installing the bootloader.

  *Update*: newer curtin releases actually allow the creation of a new
  boot entry, but updates the boot menu to make PXE the default. That
  change is orthogonal to this bug.

  ***However***, this doesn't stop a new default boot entry from being
  added after deploy. If the user installs a grub package update or
  manually runs 'grub-install', booting from disk will become the
  default, and MAAS will lose control of the system.

  [Proposed Solution (er... glorified workaround)]
  The GRUB package in zesty now has support for setting the --no-nvram flag *persistently*. This is implemented via a debconf template (grub2/update_nvram). If curtin sets this flag to "false" during install, post-deploy grub updates will also pass the --no-nvram flag when running grub-install.

  This isn't a perfect solution - users can still call grub-install
  manually and omit this flag.

  [Test Case]
   - MAAS deploy an EFI system.
   - After deploy, login and run 'sudo apt --reinstall install grub-efi-$(dpkg --print-architecture)
   - Reboot and observe that the system does not PXE boot.

  [Regression Risk]
   - The GRUB implementation does not change the defaults of the package. The user would need to opt-in to the "grub2/update_nvram=false". This option is also only presented to users who specifically request a low debconf priority (e.g. expert mode installs).
   - XXX curtin risk XXX

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