Upgrades from Focal to Jammy pull in Postfix

[Robie Basak]

Steps to reproduce:

lxc launch ubuntu:focal reproducer
lxc exec reproducer bash
do-release-upgrade -d

Expected: no Postfix debconf prompt
Actual: Postfix debconf prompt

This is bad because there's a debconf prompt at all, but also that users don't really know how to respond to this one because they're not the ones demanding an MTA.

Why is Postfix being pulled in on this upgrade? After the upgrade, I see that the only thing that Recommends default-mta | mail-transport-agent is popularity-contest, so I think this package is the culprit.

In Focal, was seeded in the standard seed which is why it was installed. However, the version in Focal does not have this Recommends.

In Jammy, it is no longer seeded (https://git.launchpad.net/~ubuntu-core-dev/ubuntu-seeds/+git/platform/commit/standard?id=82c97be2eee777cb2f579474259cf86e51fe3a8f) but since it was installed previously, the upgrade causes Postfix to get installed during the upgrade process.

A possible solution is to remove the Recommends in an Ubuntu delta.

[Paride Legovini (paride)]

I think we should remove the Recommends, actually looks like we already had a delta removing it:

popularity-contest (1.70ubuntu1) groovy; urgency=low

  * Merge from Debian unstable. Remaining changes:
    - Set debconf question priority from "high" to "medium".
    - Remove mail-transport-agent recommends.

but it got lost in the 1.71ubuntu1 upload to Impish.

[Robie Basak (racb)]

Lukas FYI.

[Launchpad Janitor (janitor)]

This bug was fixed in the package popularity-contest - 1.71ubuntu3

---------------
popularity-contest (1.71ubuntu3) jammy; urgency=medium

  * Drop Recommends on "default-mta | mail-transport-agent" to prevent
    the pulling in of Postfix during a release upgrade from Focal
    (LP: #1968874).

 -- Robie Basak <email address hidden> Wed, 13 Apr 2022 13:11:12 +0100

[Robie Basak (racb)]

I missed it before, but at is also pulling in default-mta through a Recommends. Again, there was a delta in Focal, but this has been lost.

[Launchpad Janitor (janitor)]

This bug was fixed in the package at - 3.2.5-1ubuntu1

---------------
at (3.2.5-1ubuntu1) jammy; urgency=medium

  * Replace Recommends on "default-mta | mail-transport-agent" with
    Suggests to prevent this seeded package from pulling in an MTA on
    Ubuntu by default (LP: #1968874).

 -- Robie Basak <email address hidden> Thu, 14 Apr 2022 01:23:36 +0100