[Bug 1848856] Re: Upgrade from 19.04 to 19.10 with zfs on root fails with grub syntax error

[Didier Roche]

Thanks for digging into this and finding your root cause!

I'm really wondering what is causing this additional \r on that variable
compared to a standard installation, with multiple kernels and initrds,
which doesn't get this \r. Do you have any specific grub configuration
in /etc/default/grub* or anything in /boot which can lead to this? Could
be mirror-related, where grub_probe --target device returns this \r.
What's the value of $initrd_device?

The reason is that I would like to add this case to the testsuite to
ensure we don't regress it in the future and so, trying to find the root
cause (we can mock grub_probe in our testsuite to return what you got
exactly).

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https://bugs.launchpad.net/bugs/1848856

Title:
  Upgrade from 19.04 to 19.10 with zfs on root fails with grub syntax
  error

Status in grub2 package in Ubuntu:
  Confirmed

Bug description:
  At the end of the upgrade from 19.04 to 19.10, the post process of the
  update-grub reports:

  Syntax error at line 185
  Syntax errors are detected in generated GRUB config file.
  Ensure that there are no errors in /etc/default/grub
  and /etc/grub.d/* files or please file a bug report with
  /boot/grub/grub.cfg.new file attached.
  run-parts: /etc/kernel/postinst.d/zz-update-grub exited with return code 1
  dpkg: error processing package linux-image-5.3.0-18-generic (--configure):
   installed linux-image-5.3.0-18-generic package post-installation script subprocess returned error exit status 1
  Errors were encountered while processing:
   friendly-recovery
   grub-efi-amd64
   grub-efi
   grub-efi-amd64-signed
   shim-signed
   linux-image-5.3.0-18-generic

  The system used https://github.com/zfsonlinux/zfs/wiki/Ubuntu-18.04
  -Root-on-ZFS to add zfs on root to a 19.04 system.

  The syntax error in grub.cfg.new is an extra } on line 185.  However,
  comparing the grub.cfg.new to the previously generated grub.cfg under
  19.04, there is a significant quantity of configuration missing.

  Manually running update-grub generates the same error.
  /etc/default/grub is the only file changed from default installation
  to include zswap.  This file was not changed prior to upgrade.

  The error is reported during the processing of
  /etc/grub.d/10_linux_zfs which is dated October 11.  I attempted the
  upgrade on 10/18 and have done multiple updates to get the latest
  kernel and remove old kernels prior to the upgrade.  So, I believe the
  problem is with one of the upgrade modules.

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