I have yesterday updated packages and today the system cannot boot properly. After seeing the Kubuntu logo there is a black screen which shows repeatedly.

Stopped User Manager for UID 121.

Removed slice User Slice of gdm.

Created slice User Slice of gdm.

Starting User Manager for UID 121...

Started Session c3 of user gdm.

Started User Manager for UID 121.

Please see the screenshot below

enter image description here

  • 1
    Does your computer has NVIDIA graphics card? – Raffa Aug 5 '19 at 11:19
  • Yes, NVIDIA GeForce 9500M GS – Igor Sikora Aug 5 '19 at 11:27
  • What version of Kubuntu is installed? – Raffa Aug 5 '19 at 11:40
  • Sorry for messy answer - but Ubuntu is 18.04, after that I installed KDE on it - but I'm using Gnome environment. – Igor Sikora Aug 5 '19 at 11:49
  • 1
    OK, I will write an answer in a moment – Raffa Aug 5 '19 at 11:52

It seems your update included a new kernel with it. Your old NVIDIA driver, as it seems, is not compatible with the new kernel and you need to remove the driver for now.

Since you can not access the terminal right now. You need to boot into recovery mode and drop to a root shell to do that.

Please follow the steps below:

  1. Reboot your machine and hold the Shift key as soon as you pass the BIOS logo to access the GRUB boot menu. You might need to repeat this a few times until you succeed and see the boot menu.

  2. Select advanced options and hit Enter.

  3. Select the second option with (recovery mode) in front of it and hit Enter.

  4. Wait until the machine boots and another menu appears. Choose the option with drop to root shell prompt in it and hit Enter.

  5. Press Enter when it says press Enter for maintenance.

  6. Once you are presented with a command prompt, write the following command and hit Enter (this will give you read and write access to your system):

mount -o rw,remount /
  1. You will need now to purge the NVIDIA drivers from your system. To do this please write the following command and hit Enter:
apt purge nvidia-*
  1. Now you need to let ubuntu-drivers tool install the suitable driver for your card, to do so pleas write the following command and hit Enter:
ubuntu-drivers autoinstall
  1. Reboot your system.

If all goes well and your system boots normally again, you can later search for a specific compatible NVIDIA proprietary driver and install it if you wish.

  • 3
    Assuming the kernel is the culprit, you don't need to uninstall anything, just boot to an earlier kernel that is known to boot correctly, and wait for a kernel update to land to correct the problem permanently. – karel Aug 5 '19 at 12:46
  • @karel that is possible indeed if NVIDIA and display server configuration files are still intact and not modified during the update process. – Raffa Aug 5 '19 at 12:52
  • 1
    It worked, thanks! However, apparently now there are problems with internet connection, which I'll probably post later. – Igor Sikora Aug 5 '19 at 12:58
  • 1
    The sudo ubuntu-drivers autoinstall installs nVidia driver as well. I have GT620 and not much difference with nouveau and nVidia driver. I uninstalled nVidia & on reboot it defaulted to nouveau. I did not even need nomodeset which I always used to need. Then on running the autoinstall, it installed correct nVidia driver 390.xx for my older card. On reboot then it used nVidia again. – oldfred Aug 5 '19 at 15:03
  • While I performed ubuntu-drivers autoinstall, I got an error Method/usr/lib/apt/methods/http did not start correctly Method http has died unexpectedly – fsevenm Sep 11 '19 at 10:58

Try to:

  1. If possible, switch to the second terminal by pressing keys' combination: Ctrl+Alt+F2
  2. Log in
  3. Reinstall your Nvidia drivers (if you had been installed proprietary drivers) $ sudo apt purge nvidia-340 (if your driver version is 340 and is available in repositories)

    $ sudo apt-get install nvidia-340

  4. Reboot

To find what driver is available you could use command:

$ apt-cache search nvidia | grep 'binary driver'

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