Fix a broken desktop GUI

Question

I've been running 12.04 on a NVidia GPU. I attempted to install ATI's proprietary catalyst drivers and a second GPU. Now the X-desktop will not start.

1. How do I refresh the borked desktop?
2. Can NVidia and ATI's HD series coexist?

"Will not start" may be a misnomer. The background comes up but the (taskbar?) on the left doesn't come up and the icons on the desktop can't be clicked. After a timeout I get a password request but then the desktop no longer shows.

I found a message from modem-manager trying to start saying it can't find /var/run/dbus/system_bus_socket. That may or may not be helpful

lspci:

03:00.0 VGA compatible controller [0300]: NVIDIA Corporation GK106 [GeForce GTX 650 Ti] [10de:11c6] (rev a1) Subsystem: eVga.com. Corp. Device [3842:3650] Kernel driver in use: nvidia Kernel modules: nvidia_319_updates, nvidia_304, nvidia_304_updates, nouveau, ? nvidiafb

03:00.1 Audio device [0403]: NVIDIA Corporation GK106 HDMI Audio Controller [10de:0e0b] (rev a1) Subsystem: eVga.com. Corp. Device [3842:3650]

06:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Cedar [Radeon HD 5000/6000/7350/8350 Series] [1002:68f9] Subsystem: Hightech Information System Ltd. Device [1787:2291] Kernel modules: radeon 06:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Cedar HDMI Audio [Radeon HD 5400/6300 Series] [1002:aa68] Subsystem: Hightech Information System Ltd. Device [1787:aa68] Kernel driver in use: snd_hda_intel

Answer 1

I've fixed the problem.

According to answer #1 at Ubuntu 12.04 - default Radeon driver does not work at all there were some missing drivers.

To get hardware acceleration (tested on 12.04 Precise Pangolin), you need to add four more packages:

sudo apt-get install xvba-va-driver libva-glx1 libva-egl1 vainfo

After installing them, the desktop successfully completed initialization on my nVidia display (which has been plugged in all along). I suppose that was the "Magic" mentioned above. Both devices show up in lspci but I have not yet tried out two monitors. Moreover CTRL-ALT-F1 no longer opens a terminal so I can't say everything is perfect yet.

03:00.0 VGA compatible controller [0300]: NVIDIA Corporation GK106
[GeForce GTX 650 Ti] [10de:11c6] (rev a1)       Subsystem: eVga.com. Corp.
Device [3842:3650]      Kernel driver in use: nvidia    Kernel modules:
nvidia_319_updates, nvidia_304, nvidia_304_updates, nouveau, nvidiafb

03:00.1 Audio device [0403]: NVIDIA Corporation GK106 HDMI Audio
Controller [10de:0e0b] (rev a1)         Subsystem: eVga.com. Corp. Device
[3842:3650]

-- 06:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Cedar [Radeon HD 5000/6000/7350/8350 Series]
[1002:68f9]     Subsystem: Hightech Information System Ltd. Device
[1787:2291]     Kernel driver in use: radeon    Kernel modules: fglrx,
radeon 06:00.1 Audio device [0403]: Advanced Micro Devices, Inc.
[AMD/ATI] Cedar HDMI Audio [Radeon HD 5400/6300 Series] [1002:aa68]
        Subsystem: Hightech Information System Ltd. Device [1787:aa68]

Answer 2

Not sure about coexisting without lots of magic, but to get the nVidia stuff going again, try:

Ctrl-Alt-F1 to get to a virtual terminal (I assume you just have a blinking cursor with a failed X), log in and then run:

sudo apt-get purge nvidia* 
sudo apt-get install nvidia-current

And that should get you going again.

Answer 3

To reinstall a broken GUI-Desktop:

sudo apt update
sudo apt upgrade
sudo apt autoremove

sudo apt remove ubuntu-desktop
sudo apt autoremove
sudo apt install ubuntu-desktop

References:

Reinstall Gnome

Ubuntu boots to black screen with cursor after upgrade (from 18.04 to 20.04)

Ubuntu boots to a black screen with a blinking cursor after upgrading from 14.04 to 15.10

Press ALT + F3 or F4 or F5 to enter a Terminal.