desktop manager fail after a dist-upgrade

[pierrO]

Hi,
When I have rebooted after upgrading to Xenial Xerus ; in recovery mode, the system warned me of a problem loading lightdm.
I can use a shell and give the startx command which launches lxdm that I had installed before.
I do not know how to print the warning messages.
Thank for your help.

[GreyGeek]

That's often a problem with upgrading to a new release, old configurations and files are often left behind because of a variety of reasons, many not in control, or can be controlled by the installer. Lightdm was used by 14.04. 16.04 uses sddm (simple desktop display manager).
Also, 16.04 besides switching to Plasma5, has also switched from Upstart & sysVinit to Systemd.

You should disable lightdm and enable sddm.
Lightdm is controlled by Upstart, not sysVinit. So

echo "manual" | sudo tee -a /etc/init/gdm.override

The splash screen can cause some problems, so I would suggest you to
disable it. Edit the /etc/default/grub file and replace the line
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
with
GRUB_CMDLINE_LINUX_DEFAULT="quiet".

Then generate a new Grub2 config file:
sudo update-grub

After you boot up don't use startx. Instead, enable ssdm:
sudo systemctl enable sddm
sudo systemctl enable graphical.target
Then reboot.

[pierrO]

Dear GreyGeek, I have created the gdm.override file with the unique word "manual", and I have followed your instructions but on reboot, the warning messages still saying it failed to use lightdm. Then a message tell me to execute :

systemctl status lightdm.service
systemctl status gpu-manager.service

After that the system pursues the boot procedure, until he gives a message :
A start job is running for Hold until boot process finishes up
A time counter begins and never stop after 8 min.

And I must reboot with Ctrl+Alt+Suppr, because I have not access to a shell. Now I must suspend my tests, but if you have an idea to follow it would be cool for me.

[GreyGeek]

From grub select the recovery option and from there the root with shell option.

Run
journalctl -a -r
which will list all the journal entries in reverse order, listing the most recent first. Look for times which correspond to when your last boot up hung. The last process listed before your boot to root may be the culprit.

I suspect that something is blocking sddm from loading.

[pierrO]

Gpu ?

I have a problem with the root's shell in recovery mode, when I use tabs for completion, the screen is recovered by the recovery menu. Is there a link between this and that ?
So I used the recovery mode and resume and access to bash.
journalctl -a -r gives this information informations about lightdm and gpu-manager :

zeus gpu-manager[1147]: update-alternatives: erreur: pas d'alternatives pour i386-linux-gnu_gfxcore_conf
zeus gpu-manager[1147]: /etc/modprobe.d is not a file
zeus gpu-manager[1147]: /etc/modprobe.d is not a file
zeus gpu-manager[1147]: /etc/modprobe.d is not a file
zeus gpu-manager[1147]: /etc/modprobe.d is not a file
zeus gpu-manager[1147]: /etc/modprobe.d is not a file
zeus systemd[1]: Starting Detect the available GPUs and deal with any system changes...
zeus systemd[1]: Stopped Light Display Manager.
zeus systemd[1]: lightdm.service: Service hold-off time over, scheduling restart.
zeus systemd[1]: Started Manage, Install and Generate Color Profiles.
zeus dbus[846]: [system] Successfully activated service 'org.freedesktop.ColorManager'
zeus systemd[1]: lightdm.service: Failed with result 'exit-code'.
zeus systemd[1]: lightdm.service: Unit entered failed state.
zeus systemd[1]: Failed to start Light Display Manager.
zeus systemd[1]: lightdm.service: Main process exited, code=exited, status=1/FAILURE
zeus systemd[1]: Starting Light Display Manager...
zeus systemd[1]: Started Detect the available GPUs and deal with any system changes.
zeus gpu-manager[1102]: update-alternatives: erreur: pas d'alternatives pour i386-linux-gnu_gfxcore_conf
zeus gpu-manager[1102]: /etc/modprobe.d is not a file
zeus gpu-manager[1102]: /etc/modprobe.d is not a file
zeus gpu-manager[1102]: /etc/modprobe.d is not a file
zeus gpu-manager[1102]: /etc/modprobe.d is not a file
zeus gpu-manager[1102]: /etc/modprobe.d is not a file
zeus systemd[1]: Starting Detect the available GPUs and deal with any system changes...
zeus systemd[1]: Stopped Light Display Manager.
zeus systemd[1]: lightdm.service: Service hold-off time over, scheduling restart.
zeus systemd[1]: Started LSB: automatic crash report generation.
zeus apport[1046]: ...done.
zeus systemd[1]: lightdm.service: Failed with result 'exit-code'.
zeus systemd[1]: lightdm.service: Unit entered failed state.
zeus systemd[1]: Failed to start Light Display Manager.
zeus systemd[1]: lightdm.service: Main process exited, code=exited, status=1/FAILURE
zeus systemd[1]: Started LSB: daemon to balance interrupts for SMP systems.
zeus irqbalance[1044]: ...done.
zeus apport[1046]: * Starting automatic crash report generation: apport
zeus systemd[1]: Started LSB: Set the CPU Frequency Scaling governor to "ondemand".
zeus irqbalance[1044]: * Starting SMP IRQ Balancer: irqbalance
zeus systemd[1]: Starting Light Display Manager...



With systemctl status gpu-manager.service I obtain :
● gpu-manager.service - Detect the available GPUs and deal with any system changes
Loaded: loaded (/lib/systemd/system/gpu-manager.service; enabled; vendor preset: enabled)
Active: inactive (dead) since jeu. 2016-10-06 10:04:43 CEST; 14min ago
Process: 1224 ExecStart=/usr/bin/gpu-manager --log /var/log/gpu-manager.log (code=exited, status=0/SUCCESS)
Main PID: 1224 (code=exited, status=0/SUCCESS)

oct. 06 10:04:43 zeus systemd[1]: Starting Detect the available GPUs and deal with any system changes...
oct. 06 10:04:43 zeus gpu-manager[1224]: /etc/modprobe.d is not a file
oct. 06 10:04:43 zeus gpu-manager[1224]: /etc/modprobe.d is not a file
oct. 06 10:04:43 zeus gpu-manager[1224]: /etc/modprobe.d is not a file
oct. 06 10:04:43 zeus gpu-manager[1224]: /etc/modprobe.d is not a file
oct. 06 10:04:43 zeus gpu-manager[1224]: /etc/modprobe.d is not a file
oct. 06 10:04:43 zeus gpu-manager[1224]: update-alternatives: erreur: pas d'alternatives pour i386-linux-gnu_gfxcore_conf
oct. 06 10:04:43 zeus systemd[1]: Started Detect the available GPUs and deal with any system changes.
oct. 06 10:04:43 zeus systemd[1]: gpu-manager.service: Start request repeated too quickly.
oct. 06 10:04:43 zeus systemd[1]: Failed to start Detect the available GPUs and deal with any system changes.

and with systemctl status lightdm.service :
● lightdm.service - Light Display Manager
Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; vendor preset: enabled)
Active: inactive (dead) (Result: exit-code) since jeu. 2016-10-06 10:04:43 CEST; 12min ago
Docs: man:lightdm(1)
Process: 1250 ExecStart=/usr/sbin/lightdm (code=exited, status=1/FAILURE)
Process: 1246 ExecStartPre=/bin/sh -c [ "$(basename $(cat /etc/X11/default-display-manager 2>/dev/null))" = "lightdm" ] (code=exited, status=0/SUCCESS)
Main PID: 1250 (code=exited, status=1/FAILURE)

oct. 06 10:04:43 zeus systemd[1]: lightdm.service: Unit entered failed state.
oct. 06 10:04:43 zeus systemd[1]: lightdm.service: Failed with result 'exit-code'.
oct. 06 10:04:43 zeus systemd[1]: lightdm.service: Service hold-off time over, scheduling restart.
oct. 06 10:04:43 zeus systemd[1]: Stopped Light Display Manager.
oct. 06 10:04:43 zeus systemd[1]: lightdm.service: Start request repeated too quickly.
oct. 06 10:04:43 zeus systemd[1]: Failed to start Light Display Manager.

%%%%%%%%%%%
What are GPUs ?

[pierrO]

I have installed lightdm-gtk-greeter, after reboot a shell opened, I update packages with some linked to lightdm, and when the reboot was done I had a login screen.
But I can not choose any other desktop manager than Lxde, OpenBox and a third but not KDE.
In Lxde, I can launch Kde applications, I installed the meta package kde which was extraneously uninstalled. On the control panel of Kde, the screen connexion is fixed on SDDM, and not the login screen I saw.

[pierrO]

[Solved]

OK, I have updated the system, installed lightdm-gtk-greeter, the meta package of KDE which was extraneously not installed. After reboot I obtain a login screen and choose the Plasma Desktop (I searched KDE name in vain) and WHAOU a new KDE desktop !!!

[GreyGeek]

Good!
On the reboot you let extraneous msgs deflect you from enabling seem and the graphical.target and then rebooting again.
I suspect that if you check the default-display-manager again you will find that your box is still using lightdm It's little gotcha's like that which cause me to favor a clean install over an upgrade. Your installation may continue to work well, or not, depending on past changes you made in configuration or sources of installed packages.


Sent from my iPhone using Tapatalk

[pierrO]

How can I check and choose the default desktop manager ?

[GreyGeek]

How can I check and choose the default desktop manager ?

You can check it with this command:
:~$ cat /etc/X11/default-display-manager
I've never changed it so I'd have to do some research to find out how. Google "how to set kubuntu display manager" and see what you can find.

[pierrO]

You suspected right ! lightdm is still the desktop manager.

[vinnywright]

try running

sudo dpkg-reconfigure sddm

VINNY

[pierrO]

OK Fine Thank you