[Bug 1675079] Re: 16.04 LTS Partition /boot fills up with Kernel images, gets underwear in a twist

[private_lock]

I'm hitting two distinct errors here:

1) Accepting the updates from the GUI-notification, all my kernels over
the past months get marked as "manual" - though I have the strong
feeling, they should be automatic and only kept until superseded by jet
more updates:

root at Meerschweinchen:/boot# apt-mark showmanual 'linux-image-.*'
linux-image-5.4.0-52-generic
linux-image-5.4.0-54-generic
linux-image-5.4.0-56-generic

2) Trying to mark an old kernel as "auto" will still not *MANUALLY* "autoremove":
root at Meerschweinchen:/boot# sudo apt-mark auto linux-image-5.4.0-51-generic
linux-image-5.4.0-51-generic wurde bereits auf automatisch installiert gesetzt.
root at Meerschweinchen:/boot# apt-mark showauto 'linux-image-.*'
linux-image-5.4.0-51-generic
linux-image-generic
root at Meerschweinchen:/boot# apt-get autoclean
Paketlisten werden gelesen... Fertig
Abhängigkeitsbaum wird aufgebaut.       
Statusinformationen werden eingelesen.... Fertig
root at Meerschweinchen:/boot# apt-get autoremove
Paketlisten werden gelesen... Fertig
Abhängigkeitsbaum wird aufgebaut.       
Statusinformationen werden eingelesen.... Fertig
0 aktualisiert, 0 neu installiert, 0 zu entfernen und 0 nicht aktualisiert.

This system is:
root at Meerschweinchen:/boot# uname -a
Linux Meerschweinchen 5.4.0-56-generic #62-Ubuntu SMP Mon Nov 23 19:20:19 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
root at Meerschweinchen:/boot# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.1 LTS
Release:        20.04
Codename:       focal

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https://bugs.launchpad.net/bugs/1675079

Title:
  16.04 LTS Partition /boot fills up with Kernel images, gets underwear
  in a twist

Status in unattended-upgrades package in Ubuntu:
  Fix Released
Status in update-manager package in Ubuntu:
  Fix Released
Status in unattended-upgrades source package in Xenial:
  Fix Released
Status in update-manager source package in Xenial:
  Fix Released
Status in unattended-upgrades source package in Artful:
  Won't Fix
Status in update-manager source package in Artful:
  Fix Released

Bug description:
  [Impact]

   * Update-manager and unattended-upgrades install many kernel packages during the lifetime of a release but does not remove them automatically leading to those packages filling disk space potentially completely filling /boot and making the system unable to install updates or even boot.
   * Stable release users are impacted by this bug for years and their systems already collected many autoremovable unused kernel packages, thus they would benefit from backporting the fix greatly.
   * The bug is fixed by removing autoremovable (not currently booted) kernel packages when running unattended-upgrades or update-manager. Update manager offers the kernel removals when there are other updates to be installed.

  [Test Case]

   1. Install kernel packages to be removed, mark them auto-installed
  and run apt's kernel hook script to make apt consider them
  autoremovable:

    sudo apt install -y linux-image-extra-4.4.0-92-generic linux-image-extra-4.4.0-93-generic
    sudo apt-mark auto linux-image-extra-4.4.0-92-generic linux-image-extra-4.4.0-93-generic
    sudo /etc/kernel/postinst.d/apt-auto-removal

   2. Also downgrade a package to be upgraded:

     sudo apt-get install -y --allow-downgrades ca-
  certificates=20160104ubuntu1

   3. (update-manager). Run update-manager and observe that kernel
  packages are offered for removal in Details of updates.

    sudo update-manager

   4. (update-manager) Click on Install Now and observe that the kernel
  packages are removed.

   3. (unattended-upgrades) Run unattended-upgrades manually and observe
  the removal of the autoremovable kernel packages:

    sudo unattended-upgrade -v

  [Regression Potential]

   The change may cause update-manager or unattanded-upgrades to remove
  used kernel packages or fail to install other package updates.

  [Other Info]

  The unattended-upgrades fix is uploaded with many other fixes and
  those may cause regressions in other areas in unattended-upgrades.

  [Original bug text]

  On a 16.04LTS system, the /boot partition will eventually fill with
  Kernel images, until the point where "apt-get autoremove" can't
  complete.

  This issue has previously been reported as fixed, but it is not fixed:
  https://bugs.launchpad.net/ubuntu/+source/unattended-upgrades/+bug/1357093

  Generally what I see is the final kernel image that fills the drive is
  incompletely installed (the header package does not make it).  "apt-
  get autoremove" tries to work, but fails.  I must manually remove
  kernel images to free enough space.

  I see this on a machine used by my elderly parents, where 'Download
  and install updates automatically' is set.  And on my home machines,
  where the setting is elsewhere.

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