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I tried the solution posted in Ubuntu 15.10 random lightdm crash but when I got to the step of reinstalling lightdm* a couple errors came up (I didn't write down what they were). Now I'm stuck in GNOME with the following issues:

  1. Removing/purging lightdm* doesn't seem to be working. Several packages say "is not installed, so not removed". Another package has unmet dependencies (plasma-workspace) but it is not going to be installed.

  2. If I try to dpkg-reconfigure gdm and set it to lightdm, when I reboot the computer tries to start in "low graphics" mode and basically fails to start lightdm. Would love some help here...

For the record, I'm running an HP Spectre x360.

john@john-desktop:~$ sudo apt-get remove lightdm*
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'liblightdm-gobject-0-0' for regex 'lightdm*'
Note, selecting 'ubuntustudio-lightdm-theme' for regex 'lightdm*'
Note, selecting 'lightdm-gtk-greeter-config' for regex 'lightdm*'
Note, selecting 'razorqt-lightdm-greeter-config' for regex 'lightdm*'
Note, selecting 'liblightdm-qt5-3-0' for regex 'lightdm*'
Note, selecting 'liblightdm-qt-3-0' for regex 'lightdm*'
Note, selecting 'mythbuntu-lightdm-theme' for regex 'lightdm*'
Note, selecting 'lightdm-gtk-greeter' for regex 'lightdm*'
Note, selecting 'gir1.2-lightdm-1' for regex 'lightdm*'
Note, selecting 'liblightdm-qt5-3-dev' for regex 'lightdm*'
Note, selecting 'lightdm-remote-session-uccsconfigure' for regex 'lightdm*'
Note, selecting 'liblightdm-qt-3-dev' for regex 'lightdm*'
Note, selecting 'lightdm-kde-greeter' for regex 'lightdm*'
Note, selecting 'lightdm-gtk-greeter-settings' for regex 'lightdm*'
Note, selecting 'ubuntu-mate-lightdm-theme' for regex 'lightdm*'
Note, selecting 'razorqt-lightdm-greeter' for regex 'lightdm*'
Note, selecting 'liblightdm-gobject-1-dev' for regex 'lightdm*'
Note, selecting 'lightdm-gtk' for regex 'lightdm*'
Note, selecting 'liblightdm-qt-1-0' for regex 'lightdm*'
Note, selecting 'lightdm-webkit-greeter' for regex 'lightdm*'
Note, selecting 'liblightdm-qt-dev' for regex 'lightdm*'
Note, selecting 'lightdm-remote-session-freerdp' for regex 'lightdm*'
Note, selecting 'liblightdm-gobject-1-doc' for regex 'lightdm*'
Note, selecting 'lightdm-greeter' for regex 'lightdm*'
Note, selecting 'lightdm' for regex 'lightdm*'
Note, selecting 'liblightdm-qt-0-0' for regex 'lightdm*'
Note, selecting 'liblightdm-gobject-1-0' for regex 'lightdm*'
Note, selecting 'liblightdm-qt-1-dev' for regex 'lightdm*'
Package 'liblightdm-qt-1-0' is not installed, so not removed
Package 'liblightdm-qt-1-dev' is not installed, so not removed
Package 'liblightdm-qt-3-dev' is not installed, so not removed
Package 'liblightdm-gobject-0-0' is not installed, so not removed
Package 'liblightdm-qt-0-0' is not installed, so not removed
Package 'lightdm-remote-session-freerdp' is not installed, so not removed
Package 'lightdm-remote-session-uccsconfigure' is not installed, so not removed
Package 'lightdm-gtk' is not installed, so not removed
Note, selecting 'qlubuntu-default-session' instead of 'razorqt-lightdm-greeter-config'
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 sddm-theme-breeze : Depends: plasma-workspace but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

EDIT

Thanks for the help. I encountered some errors at the 'sudo dpkg --configure -a' step, and decided not to continue until I get some feedback on them. Here are the errors:

john@john-desktop:~$ sudo dpkg --configure -a
dpkg: dependency problems prevent configuration of sddm-theme-breeze:
 sddm-theme-breeze depends on plasma-workspace; however:
  Package plasma-workspace is not installed.

dpkg: error processing package sddm-theme-breeze (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of sddm:
 sddm depends on sddm-theme-breeze | sddm-theme; however:
  Package sddm-theme-breeze is not configured yet.
  Package sddm-theme is not installed.
  Package sddm-theme-breeze which provides sddm-theme is not configured yet.

dpkg: error processing package sddm (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of qlubuntu-default-session:
 qlubuntu-default-session depends on sddm; however:
  Package sddm is not configured yet.

dpkg: error processing package qlubuntu-default-session (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 sddm-theme-breeze
 sddm
 qlubuntu-default-session
john@john-desktop:~$ 

EDIT

I was able to purge the offending packages, although in the reverse order you listed them. Everything else was working fine until the echo commands:

john@john-desktop:~$ echo '[SeatDefaults]' | sudo tee /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
tee: /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf: No such file or directory
[SeatDefaults]
john@john-desktop:~$ echo 'greeter-session=unity-greeter' | sudo tee -a /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
tee: /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf: No such file or directory
greeter-session=unity-greeter

I have no lightdm.conf.d directory. I do have a lightdm-gtk-greeter.conf file and a lightdm-gtk-greeter.conf.d directory which has 01_ubuntu.conf, 30_lubuntu.conf, and 99_ubuntu-mate.conf. Should I redirect the echo commands (or just write those lines) in one of these other files? I don't know if any are equivalent to 50-unity-greeter.conf.

john@john-desktop:/etc/lightdm$ ls
lightdm.conf                lightdm-webkit-greeter.conf
lightdm-gtk-greeter.conf    mythbuntu-lightdm-gtk-greeter.conf
lightdm-gtk-greeter.conf.d  users.conf

For a better description of what happens when I try to start after switching to lightdm, it first pops up a dialogue saying that it could not properly detect my graphics and input devices, so I will have to configure those myself. When I close out of that, it then says that it will try to start in low graphics mode. I ultimately have to ctrl+alt+F2 to a new terminal and reconfigure back to gdm to get out of it.


EDIT 02-15-2016

Still looking for help here. In addition to the above, I've tried manually creating lightdm.conf.d and 50-unity-greeter.conf and then continuing with the reconfigure back to lightdm, but still no dice. When I try to start in lightdm, I still get the 'could not detect your display, graphics, and input devices' error and then asking if it should start in low-graphics mode. When I ctrl+alt+F1 to the terminal, the following is shown ...

[ OK ] Started ACPI event daemon. 
[ somenumber] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in base.adjusted_mode.crtc_clock (expected 138780, found 92519)
[ somenumber] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in base.adjusted_mode.crtc_clock (expected 138780, found 92519)
[ somenumber] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in base.adjusted_mode.crtc_clock (expected 138780, found 92519)

EDIT 02-16-2016 I followed all the instructions in EDIT 2 (in the answer section) and no errors were thrown. The Intel packages installed flawlessly with little green checkmarks for each step in their GUI. I had the right directory structure for lightdm.conf.d and the echo commands went through. Nevertheless, when I did the sudo dpkg-reconfigure lightdm command and rebooted, it once again tried to start in low-graphics mode. I appreciate all the help so far and, believe me, I wish I could mark this as resolved - but alas, I need more help. What are the next steps?


EDIT 02-19-2016

So I finally gave up and just reinstalled Ubuntu 15.10. First thing I did after the new install was to upgrade the Intel graphics drivers, as suggested below. Hopefully I will not see the crash-to-login behavior as I did before. If I do, I'll come back to this post and will try again, without using the wildcard after the lightdm package name.

I don't think I should necessarily mark this as resolved, but if one of the mods wants to mark it as inactive, that's fine. There's good info here, but I wasn't ultimately able to get down to the root of the problem I was having. Thanks, mchid, for all your help.

  • Also, the Ubuntu Software center is not functioning properly - it says there is a problem with the software currently installed and asks if I want to repair it, but I've tried that and the repair fails. – beersteiner Jan 26 '16 at 20:25
  • I have updated the post, see the EDIT: – mchid Feb 9 '16 at 21:10
  • I don't see where you updated it since my last attempt. I did purge the offending packages. Then, I was able to run all of your listed commands for restoring unity-greeter without error up to the two echo ... commands. Both of those commands returned a 'No such file or directory error'. – beersteiner Feb 11 '16 at 12:43
  • I tried (1) reconfiguring lightdm anyway and chose lightdm, but lightdm wouldn't start again, so I'm still in gdm. Also, during the 'install --reinstall lightdm unity-greeter' command I'm asked to choose gdm or lightdm - I tried choosing lightdm and again, failure to start lightdm. I am happy to report, however, that my software manager seems to be functioning again and I am not getting internal errors anymore, so the system itself seems to be relatively healthy. Just can't figure out how to get unity back. – beersteiner Feb 11 '16 at 12:43
  • 1
    Possible duplicate of How to fix "The system is running in low-graphics mode" error? – mchid Feb 15 '16 at 8:51
1

Fixing a package management problem can sometimes be a bit tedious but it will all work out in the end. I'm pretty experienced at interpreting apt-get and dpkg error messages.

The problem you face right now is that your apt-get remove lightdm* command contains a wild-card * and so apt-get is trying to remove way more packages than it reasonably should. Most of the time it is best just to use the package name only when this type of situation presents itself.

Try this instead.

Run the following commands to restore the unity-greeter:

sudo apt-get clean
sudo apt-get update
sudo dpkg --configure -a
sudo apt-get -f install
sudo apt-get dist-upgrade 
sudo apt-get purge lightdm
sudo apt-get install --reinstall lightdm unity-greeter
echo '[SeatDefaults]' | sudo tee /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
echo 'greeter-session=unity-greeter' | sudo tee -a /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
sudo dpkg-reconfigure lightdm

Select lightdm and reboot.

If you are still having flickering and graphics problems, you will need to post your hardware specs like your GPU model etc.

Please post any errors, thanks!


EDIT:

Purge the offending packages like so and then continue with the instructions above:

sudo dpkg -P sddm-theme-breeze
sudo dpkg -P sddm
sudo dpkg -P qlubuntu-default-session

Please post any errors.


EDIT 2

First, fix your drivers:

sudo apt-get install gdebi
wget https://download.01.org/gfx/ubuntu/15.10/main/pool/main/i/intel-linux-graphics-installer/intel-linux-graphics-installer_1.2.1-0intel2_amd64.deb
sudo gdebi intel-linux-graphics-installer_1.2.1-0intel2_amd64.deb
wget --no-check-certificate https://download.01.org/gfx/RPM-GPG-KEY-ilg -O - | sudo apt-key add -
wget --no-check-certificate https://download.01.org/gfx/RPM-GPG-KEY-ilg-2 -O - | sudo apt-key add -
sudo intel-linux-graphics-installer &

Follow the instructions and click to install the packages. When it is done, reboot.

Next, get rid of that mythbuntu lightdm theme and reinstall all the regular stuff:

sudo apt-get purge mythbuntu-lightdm-theme
sudo apt-get install --reinstall lightdm unity-greeter ubuntu-desktop

Finally, make sure you have the proper files:

echo '[SeatDefaults]' | sudo tee /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
echo 'greeter-session=unity-greeter' | sudo tee -a /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
sudo dpkg-reconfigure lightdm

If you get an error for no file exists, run the following command and then run the echo commands again:

sudo mkdir /etc/lightdm/lightdm.conf.d

Finally, make sure lightdm is set as the default:

sudo dpkg-reconfigure lightdm

Use arrow keys to highlight lightdm if not highlighted and then press TAB and then press ENTER.

When all is said and done, reboot.

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