unattended do-release-upgrade to cosmic asks about /etc/gdm3/custom.conf

[Paul Larson]

I'm trying to do some automated testing that involved upgrading a system from bionic to cosmic, so I need it to not ask for user input.

Before running do-release-upgrade, the system got a fresh dist-upgrade and reboot.

To avoid interactive responses, I'm using:
$ sudo do-release-upgrade -d -f DistUpgradeViewNonInteractive

Part way through the upgrade, I do get prompted for something though:
Setting up gdm3 (3.30.1-1ubuntu1) ...

Configuration file '/etc/gdm3/custom.conf'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ? Your options are:
    Y or I : install the package maintainer's version
    N or O : keep your currently-installed version
      D : show the differences between the versions
      Z : start a shell to examine the situation
 The default action is to keep your current version.
*** custom.conf (Y/I/N/O/D/Z) [default=N] ?

I also found this in /var/log/dist-upgrade/main.log:
2018-10-12 16:36:44,910 WARNING got a conffile-prompt from dpkg for file: '/etc/gdm3/custom.conf'
2018-10-12 16:36:49,915 ERROR error 'a bytes-like object is required, not 'str'' when trying to write to the conffile

Shouldn't the '-f DistUpgradeViewNonInteractive' have prevented this from getting asked?

[Jeremy Bícha (jbicha)]

Maybe we should set the dpkg options --force-confdef,confnew

https://bazaar.launchpad.net/~ubuntu-core-dev/ubuntu-release-upgrader/trunk/view/head:/DistUpgrade/DistUpgradeViewNonInteractive.py#L74

https://manpages.debian.org/unstable/dpkg#OPTIONS

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Paul Larson (pwlars)]

I think that will work. I tried enabling these settings and it completed this time