Ubuntu 16.04 - Unity desktop session broken when using non-LightDM as X Display Manager

[林博仁(Buo-ren, Lin)]

As title, you'll only see your desktop file icons, no launcher and title/indicator bar are displayed.

You can only reproduce this issue when you choose non-LightDM DMs as well as the default X display manager

* SDDM: reproduced
* GDM3: not even launch-able on my system so can't verify
* LXDM: reproduced

This issue doesn't exist in Ubuntu 15.10, only in 16.04

## Workaround ##
* Switch to LightDM

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: sddm 0.13.0-1ubuntu5
Uname: Linux 4.5.0-buo-ren-vanilla-intel-ivybridge-optimized x86_64
ApportVersion: 2.20.1-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Apr 12 20:17:23 2016
InstallationDate: Installed on 2016-01-07 (95 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
SourcePackage: sddm
UpgradeStatus: Upgraded to xenial on 2016-04-07 (4 days ago)

[Launchpad Janitor (janitor)]

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

[Patola (patola)]

This entry in askubuntu seems to be related to this bug entry: http://askubuntu.com/questions/449845/problems-after-upgrading-to-14-04-only-background-and-pointer-after-login/

[Patola (patola)]

Sorry... I pasted the wrong link. The right one is this one: http://askubuntu.com/questions/760043/ubuntu-16-04-unity-desktop-environment-doesnt-load-after-fresh-install

[Torbjörn Lönnemark (tobbez)]

No, that linked issue seems to be another problem.

For this bug's issue, manually starting Unity as specified in the linked question works, while it doesn't for the person asking there (Unity crashes with an Illegal instruction).

On a side note the the desktop context menu works.

[MAWSpitau (marcel-spitau)]

Same problem here. I would like to use unity, but lightdm starts in a low grafics mode... Only sddm ist able to start the computer, but not unity. Which files, logs or what ever do you need?

[林博仁(Buo-ren, Lin) (buo-ren-lin)]

UPDATE: also reproducible on LXDM. I've mark all possibly relevant packages.

[Kanwar Singh (kssgill)]

sddm to unity broken. This temporarily gets me working:

right click and open shell
run

setsid unity

gets me back working in unity.

[Sebastien Bacher (seb128)]

that looks similar to bug #1293629, are those settings the XDG_CURRENT_DESKTOP env variable?

[MAWSpitau (marcel-spitau)]

In my case:

% echo $XDG_CURRENT_DESKTOP
Unity

[Launchpad Janitor (janitor)]

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

[Alejandro Dubrovsky (alito-organicrobot)]

For the people like me who have trouble finding how to switch to lightdm:

    sudo dpkg-reconfigure lightdm

but also remember to:

    sudo systemctl enable lightdm.service

You also might have to install lightdm before either of these if you didn't have it installed previously:

    sudo apt install lightdm

Afterwards, reboot.

[Nathan Adams (nadams)]

Alejandro's instructions did not restore Unity for me.

But to make the process easier for those that want to try, here they are in an easy to copy & paste format:

sudo apt install lightdm
sudo dpkg-reconfigure lightdm
sudo systemctl enable lightdm.service
sudo reboot

[Nathan Adams (nadams)]

I am not entirely sure what corrected the problem, but here are all of the steps I performed:

sudo apt-get install lightdm
sudo dpkg-reconfigure lightdm
sudo systemctl enable lightdm.service
sudo reboot

rm -rf .cache/compizconfig-1
rm -rf .compiz
rm -rf .Xauthority
rm -rf .config/autostart
dconf reset -f /org/compiz
setsid unity

At this point, Unity sprang to life for me.

[Robert Phair (rphair)]

I am also unhappy to confirm this problem but happy to find that this is a corroborated bug. As the OP reports, "gdm3" hangs the system before the Unity desktop comes up, and trying to use "sddm" starts an X session without any window management.

[Jim Hargrove (jhargrove)]

Megathanks to Nathan Adams for post #14 on this page. My Unity desktop had been functioning perfectly since upgrading to 16.04 nearly 10 months ago, but it suddenly broke yesterday for no reason I can fathom. (Last system action I had performed was to enable the system firewall - ufw.) I tried uninstalling and reinstalling Unity and LightDM, but neither action solved the problem

Then I entered each of Nathan's 10 lines above in a terminal, and when the last line executed, Unity sprang back to life. Thanks, Nathan!

[Mohammad Anwar Shah (mohammadanwarshah)]

I had all things done, lightdm installed, removed dotfiles, but didn't work. If I run lightdm as root, it starts and allows me to login.

Only the following command fixes it, which sets the lightdm as the default display manager. But I wanted to used sddm instead, because it works better with my non-functional laptop display.

    sudo dpkg-reconfigure lighdm

and selecting lightdm as the default.

[Mohammad Anwar Shah (mohammadanwarshah)]

Not completely non-lightdm, Unity session can be started using gdm3. Only sddm has problem starting either GNOME3 or Unity session

[Igor (cryptor1)]

@nadams
The only steps I've performed from your list to fix the issue are:

rm --recursive ~/.cache/compizconfig-1
rm --recursive ~/.Xauthority
dconf reset -f /org/compiz
setsid unity

I don't think there is a need to remove ~/.config/autostart directory

[Chris Guiver (guiverc)]

Thank you for reporting this bug to Ubuntu.

Ubuntu 16.04 (xenial) reached end-of-standard-support on April 29, 2021.

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.

[Launchpad Janitor (janitor)]

[Expired for sddm (Ubuntu) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for lxdm (Ubuntu) because there has been no activity for 60 days.]