ubuntu-touch-session is installable on amd64 but prevents graphical login

[Bradford Powell]

Installation of ubuntu-touch-session on an amd64 system goes off without a hitch. However, at next login, the sessions menu has two different "ubuntu touch" sessions available, which is strange... If one of these is selected, the password part of lightdm goes clear, but no desktop UI is presented. (Expected: login to a facny UI, or at least some error and falling back to the lightdm login screen)

Rebooting after this and trying to login with a standard "ubuntu" session results in the same behavior. This behavior persists after 'aptitude purge ubuntu-touch-session'

The package should probably be made uninstallable on desktop systems or else changed such that it doesn't prevent graphical logins.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubuntu-touch-session (not installed)
ProcVersionSignature: Ubuntu 3.11.0-12.19-generic 3.11.3
Uname: Linux 3.11.0-12-generic x86_64
ApportVersion: 2.12.5-0ubuntu1
Architecture: amd64
Date: Thu Oct 10 12:30:32 2013
InstallationDate: Installed on 2013-10-08 (1 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Beta amd64 (20130925.1)
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-touch-session
UpgradeStatus: No upgrade log present (probably fresh install)

[Bradford Powell (bradford-powell)]

After purging ubuntu-touch-session, there is no session menu at the lightdm login screen, but lightdm still tries to use ubuntu-touch-surfaceflinger as the default session, since that is what was written to the .dmrc in my home directory.

And lightdm is very persistant about keeping this around. If I delete the .dmrc, it gets rewritten at some point (possibly from /var/cache/lightdm/dmrc/$USER.dmrc (which I never would have guessed).

My workaround to get graphical login back was to install xfce4-session, so that there would be a session menu again and I could select 'ubuntu' (or xfce4, if I wanted) to be able to login.

So maybe there is a bug for lightdm as well about how it deals with the situation when the previously-selected session is no longer available. Instead of using the old .dmrc (or version in /var/cache/lightdm) it should probably just go with the session available if only one is available.