containerd / docker.io LP: #1870514

[Steve Langasek]

Please note that 'upgrade' and 'install' are not valid arguments to a
postinst script, so the code shown there will never be run.

https://www.debian.org/doc/debian-policy/ch-maintainerscripts.html#summary-of-ways-maintainer-scripts-are-called

The argument is always 'configure', and you need to check the contents of $2
to detect whether it is an upgrade or a fresh install.


On Thu, Dec 03, 2020 at 09:55:07PM -0500, Sergio Durigan Junior wrote:
> On Thursday, December 03 2020, Bryce Harrington wrote:
> 
> > I'm about to EOD, so in hopes of keeping activity on the bug cross
> > timezones Rick suggested identifying some specific tasks that'd help
> > move the football down the field on Proposal X.
> 
> Thanks for the email, Bryce.
> 
> > Sergio:
> >
> > Thanks again for demoing the docker commands you were using to test.
> > I've put them in the [Test Case] section of the doc.  Unfortunately I
> > get an error running the `docker run` command gives me a permission
> > denied error for OCI runtime create.  Obviously my non-docker-fu is
> > making me do something wrong.  Can you look at the test case and adjust
> > it to give a more accurately paint-by-number set of docker commands?
> 
> I could not find anything wrong with your docker commands, and I was
> able to properly start the redis service here using them.  I don't know
> if you're using a container to do this, but I'd recommend using a VM
> because of the proper separation between cgroups et al.
> 
> > ------------------------------------------------------------------------
> >
> > Sergio demoed to me what he and Paride discovered while examining
> > docker.io's prerm file (/var/lib/dpkg/info/docker.io.prerm).  Debhelper
> > automatically adds a command to stop the docker service
> > unconditionally:
> >
> >     # Automatically added by dh_systemd_start/13.2.1ubuntu1
> >     if [ -d /run/systemd/system ]; then
> >             deb-systemd-invoke stop 'docker.service' 'docker.socket' >/dev/null || true
> >     fi
> >     # End automatically added section
> >
> > This means three things.  1) Proposal A can be crossed off, 2) we might
> > potentially be able to address the problem in docker.io's maintscripts
> > better than in containerd's maintscripts by replacing this debhelper
> > logic with some conditionals like done for Proposal X, and 3) since the
> > user's installed docker.io's prerm gets run before any new package's
> > maintscripts, this means all our proposals suffer the same problem that
> > all of them will result in docker.service getting this 'stop' command at
> > least one time.
> 
> About (2), if we edit docker.io's d/rules and add:
> 
>   override_dh_systemd_start:
>           dh_systemd_start --package=docker.io -r
> 
> then docker.io's prerm script will have:
> 
>   # Automatically added by dh_systemd_start/13.2.1ubuntu1
>   if [ -d /run/systemd/system ] && [ "$1" = remove ]; then
>           deb-systemd-invoke stop 'docker.service' 'docker.socket' >/dev/null || true
>   fi
>   # End automatically added section
> 
> which is what we actually want: prerm will only stop docker.service if
> the user is removing the package, but not if it's being updated.
> 
> Of course, this doesn't really help mitigate (3), but it does mean that
> we won't really need to mess with the maintscript just to get this part
> working.
> 
> -- 
> Sergio
> GPG key ID: E92F D0B3 6B14 F1F4 D8E0  EB2F 106D A1C8 C3CB BF14
> 
> -- 
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> ubuntu-server at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/ubuntu-server
> More info: https://wiki.ubuntu.com/ServerTeam

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                   https://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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