Update-manager does not remove autoremovable kernel packages _before_installing new (kernel) packages

[Steve Langasek]

I happened to run apt manually on my system this morning to remove a package, and I was informed:

The following packages were automatically installed and are no longer required:
  linux-image-4.15.0-36-generic linux-modules-4.15.0-36-generic
  linux-modules-extra-4.15.0-36-generic

This was surprising, since I have run update-manager yesterday (with no intervening reboot), and unattended-upgrades is enabled, and both of those packages should have already removed this stale kernel before now.

After apt autoremove, my current installed packages are:

$ dpkg -l linux-image'*' | grep ^ii
ii linux-image-4.18.0-10-generic 4.18.0-10.11 amd64 Signed kernel image generic
ii linux-image-4.18.0-11-generic 4.18.0-11.12 amd64 Signed kernel image generic
ii linux-image-generic 4.18.0.11.12 amd64 Generic Linux kernel image
$

[Balint Reczey (rbalint)]

Could you please attach the relavant part of dpkg history log a and dpkg terminal log?

It is possible, that the last run of u-u/u-m installed kernel packages triggering /etc/kernel/postinst.d/apt-auto-removal which resulted kernels to be removed in the _next_ apt/u-u/u-m run.

[Steve Langasek (vorlon)]

History log:

Start-Date: 2018-11-14 17:21:44
Commandline: aptdaemon role='role-commit-packages' sender=':1.5400'
Install: linux-headers-4.18.0-11:amd64 (4.18.0-11.12, automatic), linux-image-4.
18.0-11-generic:amd64 (4.18.0-11.12, automatic), linux-modules-extra-4.18.0-11-g
eneric:amd64 (4.18.0-11.12, automatic), linux-modules-4.18.0-11-generic:amd64 (4
.18.0-11.12, automatic), linux-headers-4.18.0-11-generic:amd64 (4.18.0-11.12, au
tomatic)
Upgrade: evince:amd64 (3.30.1-1ubuntu1, 3.30.1-1ubuntu1.2), linux-headers-generic:amd64 (4.18.0.10.11, 4.18.0.11.12), linux-libc-dev:amd64 (4.18.0-10.11, 4.18.0-11.12), linux-libc-dev:i386 (4.18.0-10.11, 4.18.0-11.12), libevdocument3-4:amd64 (3.30.1-1ubuntu1, 3.30.1-1ubuntu1.2), linux-image-generic:amd64 (4.18.0.10.11, 4.18.0.11.12), linux-signed-image-generic:amd64 (4.18.0.10.11, 4.18.0.11.12), libpq5:amd64 (10.5-1, 10.6-0ubuntu0.18.10.1), evince-common:amd64 (3.30.1-1ubuntu1, 3.30.1-1ubuntu1.2), libevview3-3:amd64 (3.30.1-1ubuntu1, 3.30.1-1ubuntu1.2), linux-tools-common:amd64 (4.18.0-10.11, 4.18.0-11.12), postgresql-client-10:amd64 (10.5-1, 10.6-0ubuntu0.18.10.1), linux-generic:amd64 (4.18.0.10.11, 4.18.0.11.12)
End-Date: 2018-11-14 17:24:10

Start-Date: 2018-11-15 08:39:50
Commandline: apt autoremove --purge
Requested-By: vorlon (1000)
Purge: linux-modules-extra-4.15.0-36-generic:amd64 (4.15.0-36.39), linux-modules-4.15.0-36-generic:amd64 (4.15.0-36.39), linux-image-4.15.0-36-generic:amd64 (4.15.0-36.39)
End-Date: 2018-11-15 08:40:08

So yes, it's possible that this was only a candidate for autoremoval /after/ the previous run of update-manager had finished.

[Steve Langasek (vorlon)]

(In which case, I think this still warrants improvement, since AIUI the next run of update-manager will do removals after installations, which means a high water mark of 4 kernels rather than 3 which is what we want)

[Balint Reczey (rbalint)]

@vorlon: OK, let's use this bug to track the improvement for u-m.

While triaging I found LP: #1803749 , which you may have hit if you have Unattended-Upgrade::Remove-New-Unused-Dependencie set to False. Is that the case on your system?

[Steve Langasek (vorlon)]

$ grep -r Remove-New /etc/apt
/etc/apt/apt.conf.d/50unattended-upgrades://Unattended-Upgrade::Remove-New-Unused-Dependencies "false";
$

So it appears this is commented out.

[Balint Reczey (rbalint)]

In my tests u-u successfully removed the kernels as new unused packages even when hitting LP: #1803749 for the record.

[Balint Reczey (rbalint)]

@vorlon: OK, being commented out (and not set elsewhere) makes it default to True.
The misleading comment is fixed in later releases.