No Display Manager in Kubuntu 16.04 After Upgrade From Kubuntu 15.10

[Stephen Morris]

On 01/06/16 08:46, Clay Weber wrote:
> On Wednesday, June 1, 2016 7:38:14 AM EDT Stephen Morris wrote:
>> Hi,
>>
>>       After receiving notification that there was an upgrade for Kubuntu
>> available (not that I actually have Kubuntu installed, I have Ubuntu
>> installed with KDE installed as an addon), I ran a sudo
>> do-release-upgrade to undertake the upgrade. This process downloaded
>> between 2500 - 2600 packages.
>>
>>       After the upgrade, when I boot into the os, the boot process wants
>> to start SDDM but the start fails, and every re-attempt to start it
>> fails. Using systemctl to attempt to start the service manually fails
>> with no meaningful messages, and systemctl status sddm.service doesn't
>> show any meaningful messages either. If I issue the command, systemctl
>> start lightdm.service, that starts the DM quite happily.
>>
>>       I have checked /etc/X11/default-display-manager and that had the
>> command /usr/bin/lightdm as the display manager to launch, but that
>> location in not the location where lightdm is installed. I have replaced
>> this command with /usr/sbin/lightdm, but on a reboot the boot process
>> still tries to unsuccessfully load SDDM. I have also noticed that the
>> location of SDDM, unlike Lightdm, is actually /usr/bin/sddm.
>>
>>       Is anyone able to shed some light on why the 16.04 boot wants to
>> always start SDDM even though the default display manager is set to
>> lightdm, and also why sddm cannot actually start? Could it be that the
>> sddm.service process is looking for sddm in /usr/sbin when it is
>> actually in /usr/bin, and if so, would a symlink in /usr/sbin back to
>> /usr/bin/sddm rectify the issue?
>>
>> regards,
>>
>> Steve
> My guess, not knowing exactly how you installed Plamsa desktop as an "addon"
> would be that though sddm was installed it may not have been registered or
> activated or whatever with systemd perhaps?  "meaningless" output might
> actually be useful here.
When I installed 15.10 I installed Ubuntu 15.10, then after installation 
I installed ODE from the repositories as opposed to actually installed 
Kubuntu 15.10. ODE was working fine in 15.10 with lightdm as the display 
manager.
>
> $ sudo systemctl start sddm
> shows nothing?
Issuing this command just produces a message that it errored with 
exit-code and status = 1/failed. It also produced messages that the wait 
time was over and it was restarting the service, then a message that 
Saddam had been stopped, followed by a message that a restart of Saddam 
was attempted to soon. All 3 messages had exactly the same timestamp.
I could write the exact messages down and add them to the mail if we 
need them. My mail system is running in Fedora, which is on the same 
physical machine as Ubuntu, and I'm tri-booting between Windows 10, 
Fedora and Ubuntu.
One thing I have also noticed is that if the command sudo systemctl 
status Saddam.service is issued the first thing it does is check 
/etc/X11/default-display-manager to see if it contain /usr/bin/Saddam 
and if so it says everything is ok and it can be used as a plugin to 
another process(I'd need to check again exactly what this process is) 
and if its not set to that it flags and error, but either way it 
indicates that Saddam can't be started.
>
> You can try this to register sddm in systemd:
>
> $ sudo systemctl enable sddm.service -f
>
> You can also Try running
>
> $ sudo dpkg-reconfigure lightdm  ## or sddm
>
> this should bring up a dialog to choose which login manager to use as default.
> You should be able to select lightdm which is the default for Ubuntu anyway.
I issued the sudo dpkg-reconfigure command and that process put 
/usr/bin/Saddam or /usr/sbin/lightdm into 
/etc/X11/default-display-manager depending on which one was selected as 
the default. Given that on my system /etc/X11/default-display-manager 
had /usr/bin/lightdm it looks to me like 16.04 has installed lightdm 
into a different location to where it was in 15.10 and the upgrade has 
set /etc/X11/default-display-manager to reflect the new location.
>
>
> I am not sure if the  /etc/X11/default-display-manager specifies what happens
> when you use the start x manually rather than what the init starts up.
I'm not explicitly using startx manually. What I have now found after 
using dpkg-reconfigure is that if the default dm is lightdm, the boot 
process tries to start Saddam regardless, attempts six times to do so 
and then gives up, dropping me into a console login prompt. If I login 
and issue sudo systemctl start lightdm.service I get th e normal lightdm 
login screen and then I can login to ODE quite happily.
If I select Saddam as the default dm in dpkg-reconfigure the boot 
process doesn't produce the errors and starts Saddam. The issue I get at 
this point seems to vary from boot to boot, the first boot produced a 
dialog saying that the graphics mode was too and I would need to 
reconfigure the options (this sounds to me like the upgrade has not 
upgraded the nvidia proprietary drivers I was using in 15.10 which were 
installed from the repository), when I pressed enter because ok was the 
only option, it then displayed a dialog with four radio buttons on it, 
but I was unable to cycle through the buttons and enter appeared to do 
nothing, so I couldn't go any further. The 2nd time I booted Saddam 
started up to the normal blank screen it displays when it is 
initializing, without any prompts of any kind, but went no further. The 
3rd time I booted it went through the same process as the 1st boot with 
the same results.
>
> I have no idea where lightdm should go, but I doubt symlinking probably will
> do nothing useful.
When I did the upgrade I specified do-release-upgrade without any 
parameters, could my issues be because I didn't explicitly tell it to do 
a workstation upgrade? If this is the case can it be redone or do I need 
to download a 16.04 DVD image and redo the install from scratch?

regards,
Steve
>