Display manager defaults to lightdm on upgrade

[Robie Basak]

When I upgraded Artful earlier today using "sudo apt upgrade", I was prompted to pick between gdm3 and lightdm. lightdm was selected by default. I suspect that if I'd been running non-interactively, lightdm would have been selected, which is incorrect for our transition to GNOME.

This machine was originally installed using an early Artful daily. I've been upgrading it regularly. Previously I had the system break due to some Unity components getting unseeded and thus autoremoved, which I reverted by downgrading ubuntu-desktop (and the seeds were fixed). On some subsequent upgrade my desktop switched from Unity to GNOME smoothly (except needing synaptics removing manually, which is known). I do not recall which display manager I was seeing at the time (though I do recall that the lock screen became the more minimal GNOME one). Then, today, on upgrade, I got asked about the display manager switch.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: ubuntu-session 3.24.1-0ubuntu11
ProcVersionSignature: Ubuntu 4.10.0-26.30-generic 4.10.17
Uname: Linux 4.10.0-26-generic x86_64
ApportVersion: 2.20.5-0ubuntu5
Architecture: amd64
CurrentDesktop: GNOME
Date: Mon Jul 10 13:03:47 2017
InstallationDate: Installed on 2017-05-11 (59 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170507)
SourcePackage: gnome-session
UpgradeStatus: No upgrade log present (probably fresh install)

[Robie Basak (racb)]

This is the situation now:

robie@xps:~$ grep 'XSession=ubuntu' /var/lib/AccountsService/users/*
XSession=ubuntu
robie@xps:~$ echo $?
0

[Robie Basak (racb)]

Note that I did select gdm3 manually at the prompt, so that is correct now.

[Ken VanDine (ken-vandine)]

Looking at your log i see:

Setting up ubuntu-session (3.24.1-0ubuntu8) ...

The script to handle the migration was added in ubuntu-session 3.24.1-0ubuntu11, which was published on 2017-07-06 (later than your upgrade log). Perhaps it had been held in artful-proposed for a couple days.

[Robie Basak (racb)]

According to my history.log, I upgraded from ubuntu-session 3.24.1-0ubuntu8 to 3.24.1-0ubuntu9 on 2017-07-03. Then from 3.24.1-0ubuntu9 to 3.24.1-0ubuntu11 on 2017-07-10 (today). I think you're looking at an older part of my log?

I only had the display manager prompt on upgrade today, defaulting to lightdm.

So it seems that I did have the migration script on upgrade today, but it didn't do the right thing (today). It could be that stepping through 3.24.1-0ubuntu8 and 3.24.1-0ubuntu9 on the way to 3.24.1-0ubuntu11 triggers the issue, though I have no particular reason to believe that. But if that is what triggers it, it's still a bug as other users might step through the same way too.

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.

Ubuntu 17.10 (artful) reached end-of-life on July 19, 2018.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test. If you then find the bug is still present in the newer Ubuntu version, please add a comment here telling us which new version it is in.