[Bug 1838525] Re: LVM setup fails to install grub on virtio storage

[Christian Ehrhardt ]

Hrm, no much output of long debugging :-/
Failing to see where/why/how the difference dconf choices are populated differently for sata-vs-virtio I started to compare things with disco ...

As expected it works there and grub-installer is called with /dev/vda as
argument.

Next I went into comparing the d-i components between disco and eoan but
other than the name change in bug 1782507 nothing seemed too related.
And this change came after this bug here reported (per paride since June
18, 2019)

Next I analyzed grub-probe behavior in the three environments eoan-sata, eoan-virtio and disco-virtio.
But this part always behaves the same reporting the volume group.

So it really seems to come down finding why d-i populated the values
differently as Rafael already assumed.

P.S. along the debugging I wondered for further work about d-i coming in
components. Is there a good way/scripts that one could use exchange
those e.g. the older/newer partman-lvm and then rebuild the ISO?

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Title:
  LVM setup fails to install grub on virtio storage

Status in debian-installer package in Ubuntu:
  New
Status in grub-installer package in Ubuntu:
  Triaged
Status in debian-installer source package in Eoan:
  New
Status in grub-installer source package in Eoan:
  Triaged
Status in debian-installer package in Debian:
  New

Bug description:
  The Eoan debian-installer ISO fails to install GRUB on LVM installs
  with virtio storage, as it runs grub-install with /dev/mapper as a
  target (a directory), even if instructed to target a device.

  The following steps to reproduce have been prepared running the
  20190730 build, but this has been broken since about June 18, 2019.
  Steps to reproduce:

  $ md5sum eoan-server-amd64.iso
  f591e30485e5f0b5117f6c116e538c42  eoan-server-amd64.iso
  $ qemu-img create -f raw disk1.img 8G
  Formatting 'disk1.img', fmt=raw size=8589934592
  $ kvm -m 1024 -boot d -cdrom eoan-server-amd64.iso -drive file=disk1.img,if=virtio

  Proceed with all the defaults. In the "Partition disk" step select
  "Guided - use entire disk and set up LVM". Go ahead accepting the
  defaults. At the "Install the GRUB boot loader" step select "/dev/vda"
  as the target device. The installer will actually run `grub-install
  --force /dev/mapper` and fail after a while. The wrong command is
  visible both in the d-i screen and by running `ps` on a different
  console.

  Full installer syslog: http://paste.ubuntu.com/p/qtZy86dTp6/

  It's interesting how this doesn't happen when not using virtio. If
  from the commands above the "if=virtio" option is dropped then
  everything works as expected. In this case the target block device is
  called /dev/sda instead of /dev/vda.

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