login screen not loading after kernel upgrade

[snerk]

after the recent kernel update to 3.13.0-27-generic my login screen no longer loads, instead im left with a text mode environment where i can log in and run 'startx' to get to my desktop. this is rather annoying. booting into the old kernel which is 3.13.0-24 all is fine...any clues?

trusty/64bit

[Snowhog]

From the "text mode environment" type:

sudo apt-get install -f
sudo apt-get update
sudo apt-get dist-upgrade

When it finishes, type:

sudo shutdown -r now

[snerk]

snowhog, thanks for the suggestion but that did nothing, theres no updates or dist-upgrades to be done
im still stuck with the text mode login

[Snowhog]

Okay, from the "text mode environment" type:

sudo apt-get install --reinstall kdm

[snerk]

kdm isnt installed , its lightdm, and as i said, when im booting into the older kernel lightdm/login screen appears as it should

[Snowhog]

Sorry. Then run:

sudo apt-get install kdm

Why? Because components of kdm are used by lightdm. If those componets were removed (by an update), then lightdm can be affected.

When kdm is installed (when lightdm is already installed), you will be asked which DM you want to use as default. Select lightdm.

[snerk]

thanks again, installing kdm seems to have done the trick!

[Snowhog]

[SteveRiley]

Why? Because components of kdm are used by lightdm. If those componets were removed (by an update), then lightdm can be affected.

That's very interesting. If LightDM needs those same components, then they should also be reinstalled by
sudo apt-get install --reinstall lightdm lightdm-kde-greeter
If not, then that would indicate a problem with LightDM's packaging.

Alternately, I wonder if something in the postinst script in KDM's package "resets" a borked configuration. If that's the case, then again, the script in LightDM's package should also have the same effect.

[Snowhog]

My commentary was 'largely' based on the fiasco when LightDM was introduced to Kubuntu 'as the default DM'. When that first occured, KDM was preemptively removed by the update in favor of LightDM. But it resulted in an incomplete installation of the components needed by LightDM, components that were part of the KDM installation. Now, all of that 'may' have been resolved, and no longer an issue. But, given that, in the OP's case, installing KDM 'fixed' his problem, well....

[SteveRiley]

Yeah, I remember reading about that. I always replace LightDM with KDM whenever I set up a Kubuntu build, though. Yes, KDM may be old and crufty and slated to be replaced by SDDM eventually. But until the switch happens, I prefer to use the default display manager provided by KDE, not some third party hack, lol.

[SteveRiley]

SDDM stuff moved to new thread: https://www.kubuntuforums.net/showthread.php?65646

[snerk]

exact same thing happened again after upgrading to 3.13.0-29
reinstalling lightdm and kdm seems to have done the trick