[Bug 2020406] Re: Release upgrade fails due to unsupported DKMS modules

[Juerg Haefliger]

So we basically have two scenarios that we need to cover:
1) upgrade of a dkms package
2) upgrade of a kernel

For #1: We are supposed to fix all dkms packages in the archive to
either a) compile properly for the new kernel or b) flag it as
unsupported so that dkms build failures are ignored. If a dkms package
upgrade results in a build failure, that's a legit failure unless it
fails for an unsupported kernel.

If a dkms package is upgraded, first the current dkms module build is
completely removed and later the upgraded dkms is rebuilt for all
installed kernels (unless it was inactive for some installed kernels or
/etc/dkms/no-autoinstall is present).

For #2: A kernel upgrade results in a rebuild of all installed (and
active) dkms modules which can fail if they are unsupported or are old
Ubuntu packages that haven't been purged. IMO this should not result in
a kernel upgrade failure but it might be too complicated to detect this
condition.

If a new kernel is installed, dkms autoinstall is called which rebuilds
all installed dkms modules for the new kernel (unless /etc/dkms/no-
autoinstall is present).

What kills us currently is #2 in combination with old and/or unsupported
DKMS packages. Using the /etc/dkms/no-autoinstall mechanism to work
around that is problematic as well because it skips the rebuild of
upgraded dkms modules and we end up with an empty output of 'dkms
status', i.e, no dkms builds at all.

ATM it's unclear to me if there's an ordering issue as well in case both
the kernel and some dkms modules are upgraded (which upgrade happens
first?). I think what we want is to always rebuild upgraded dkms modules
(so we can't use no-autoinstall) but somehow don't fail a kernel upgrade
in case of a resulting dkms build failure. Maybe downgrade that
condition to a warning rather than an upgrade failure? It really is a
dkms issue, not a kernel issue...

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https://bugs.launchpad.net/bugs/2020406

Title:
  Release upgrade fails due to unsupported DKMS modules

Status in ubuntu-release-upgrader package in Ubuntu:
  Triaged
Status in ubuntu-release-upgrader source package in Lunar:
  Triaged

Bug description:
  The kernel team takes care that any DKMS package supported by the new
  release actually compiles and works with the new kernel. We also make
  sure that DKMS packages that are obsoleted in the new release are
  updated in the current release such that they are ignored on upgrade.

  However users can have old and/or unsupported DKMS packages installed
  from different sources, not just the Ubuntu archive, which can be
  problematic. If kernel header packages are installed, the dkms post-
  install hook tries to compile all installed and enabled DKMS modules.
  On upgrade, header packages for the new kernel are installed and the
  dkms hook is invoked. If any of the installed and enabled DKMS modules
  fails to build for the new kernel, the header package installation
  fails and ultimately the whole release upgrade fails.

  To get around this problem, we propose to disable all DKMS modules
  before attempting the upgrade and re-enable them one by one afterwards
  and notify the user if any of them failed to build. Care must be taken
  that when disabling the DKMS modules, the initrds are *not* rebuilt
  (otherwise the disabled DKMS modules might be removed from the
  initrds) so that the user can fall back to a previous kernel/initrd
  should the new kernel not work for them.

  ATM, there are 46 bugs logged for the 'linux' package because of DKMS
  build failures on upgrade to Lunar:
  https://bugs.launchpad.net/ubuntu/+source/linux/+bugs?field.tag=lunar-
  upgrade-dkms-
  failure&field.omit_dupes.used=&field.status%3Alist=NEW&field.status%3Alist=INVALID&field.status%3Alist=CONFIRMED&field.status%3Alist=TRIAGED&field.status%3Alist=INPROGRESS&field.status%3Alist=FIXCOMMITTED&field.status%3Alist=INCOMPLETE_WITH_RESPONSE&field.status%3Alist=INCOMPLETE_WITHOUT_RESPONSE

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