How to fix bad display driver?

Question

I stupidly installed, on my 15.10 Ubuntu installation, Kubuntu from the command line while ignoring the warnings of broken packages or errors that happened during the install.

When I rebooted my computer, I was greeted with a super striped screen, almost like the internal hardware is bad. I know the hardware isn't bad since I'm currently running Kde, installed from an ISO, on a flashdrive on the laptop to write this. The screen looks like this:

If the picture is grainy, please ignore, the screen is accurate though in how it looks. I'm still having graphics issues so many icons and pictures right now are incredibly grainy. As if they've jumped out of the original Starcraft.

The screen above was actually my desktop as I was still able to press my windows key, open a terminal, and shut the system down from the command line. So the system is booting up fine, the graphics driver just seems to be freaking out. Also being able to press the windows key to open up the menu leads me to believe I was still booting into the default Ubuntu environment since, right now in KDE, my windows key does nothing.

During the installation I remember there being two errors that stood out:

1. The installation couldn't install something related to accounts
2. The reasoning behind the failure was a broken pipe in said accounts package

Now those errors don't really jump out as being the cause of my graphical issues so I'm incredibly confused on whats going on.

Solution

If you have access to TTY, could you post the output of:

ps ax | grep dm

Then go with:

1. Reboot and press Shift to get Grub menu.
2. Select Recovery Mode → dpkg (Repair broken packages), Reboot
3. Not yet, again reboot and press Shift to get Grub menu.
4. Select (upstart mode). (let me know)
5. Not yet, again reboot and press Shift to get Grub menu.
6. Select Recovery Mode → dpkg (Repair broken packages)

7. Drop to Shell, then run:

   sudo apt-get remove sddm
   sudo dpkg-reconfigure lightdm
   

   and set lightdm as default, then reboot.

Comments

[snorp]

This is a tad unclear to me. Did you have Ubuntu 15.10 running with Unity then decided to install Kubuntu (Plasma Desktop) on top of that? What is your hope here? Restore Ubuntu's Unity, or Restore Kubuntu's Plasma Desktop? Also, did you have an proprietary drivers? When you say you're using KDE now, how did you install that, were you able to drop to console (ctrl + alt + f1)?

[Funkyguy]

@snorp I did have unity, then install the plasma desktop. I just want to get it back to a usable state, i don't care which desktop at this point. I was using the AMD open source drivers, not proprietary. I am "using" KDE now, it is running off of a flash drive and then I boot into that

[snorp]

Have you tried dropping to console (ctrl + alt + f1 [or any f key other than f7])? If that works you could start by simply removing plasma and reinstalling unity. I can write this out if you would like but first it's useful to know if you can get to a console to interact with the live system or if you'll need to run off live media.

[user.dz]

To anyone trying to understand what's going on, this case seems to have same cause to my case here askubuntu.com/questions/697529/… but the effect is different, he got scrambled screen while I got black, white or flickering screen.