[Bug 1642298] Re: UEFI Xenial install sets computer to boot from hard disk

[Andres Rodriguez]

Hey guys.

Sorry for joining the party late. But let me see if I understand the
full extent of the problem here.

0. A machine PXE boots off MAAS, installs Ubuntu in it, grub gets
installed and configured without updating the NVRAM.

1. The machine reboots, PXE's, boots from local disk, and finishes
installation (an unnecessary step).

2. An upgrade of <grub2 package> overwrites NVRAM to boot from disk.

3. A reboot boots from disk directly and not from network.

4. If we re-deploy, the machine is told to PXE boot via the BMC.

5. If we re-deploy the machine, the machine PXE boots off MAAS again and
installs. The machine reboots and boots off the disk.

Now, the above only becomes a real problem when. The machine does not
support changing the boot order remotely via IPMI or other power
management mechanism.

 - That, however, is a certification problem. MAAS expects to be able to
control the boot order of the machine. If this is not possible, it is a
certification challenge.

That said, regardless of being able to set the boot order or not, I see
a completely different problem:

1. The administrator configured their BIOS with a specific boot order.
2. The administrator installs ubuntu, expecting their BIOS boot order configuration to remain (somewhat) unchanged (specially when it is set to boot from network first).
3. The software (grub2) overrides the BIOS' boot order to boot from disk. This overrides the fact that the administrator set the BIOS boot order to PXE first.

So, based on this, the REAL bug that needs to be fixed is that grub
needs to somewhat respect the boot order set in the BIOS. For example:

1. If BIOS Boot order before Ubuntu install is: 1. PXE, 2. HDD1, 3. HDD2
2. And we install Ubuntu on HDD2, then grub needs to /somewhat/ preserve the boot order and make it so: 1. PXE, 2. HDD2, 3. HDD1.

To conclude:
1. The real bug is in grub, and this needs to be addressed to properly preserve the boot order in a sane way if PXE/Network boot is set as the first boot type on the BIOS boot order.

2. If we want to make work arounds in the meantime, I think it is
acceptable to say that curtin should tell grub to disable nvram updating
by default, and only enabled it if the users wishes so, so we can
respect what was set on the firmware.

Either way, IMHO, the real solution is to fix grub.



** Changed in: maas
       Status: Triaged => Incomplete

** Changed in: maas
   Importance: High => Undecided

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

Title:
  UEFI Xenial install sets computer to boot from hard disk

Status in curtin:
  Confirmed
Status in MAAS:
  Incomplete
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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