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I've been using Ubuntu(12.10) for a long time, and recently, my Ubuntu went through yet another update.

The whole update prompt showed up, following by a password prompt, and finally the good ol' progress bar...

Everything went well, and later on, I shut down my computer.

The next day, I turned my PC on, went to the login screen. I went ahead, and logged in, but after that, all I could see was a black screen, and my cursor!

I checked the forums, and got various tips, none of which worked...

Now I'm stuck with an Ubuntu installation that's completely useless.

One more thing:

I even tried logging in through Guest, but same problem! :\

My Computer Specs: Motherboard: Intel DG41WV Processor: Intel Core 2 Quad Q6600 @ 2.40GHz Graphics: Intel G41 Express Chipset RAM: Dual Channel, DDR3 2*2GB (4096 MBytes) HDD: Seagate 500GB SATA (Sorry, can't get more on this)

---- DETAILED INFO ----

To be a little more precise about my problem, after I log in, I can see a black screen and my cursor. Plus, importantly, I was able to see a login screen, hence I'm sure Ubuntu is rendering properly, and also pretty sure that there's no problem with the drivers (Otherwise I shouldn't even get a login screen, right?).

Anywho, another (probably) important thing is that, after logging in, I can hit <1> and get up a recovery console.

The only thing that doesn't load is my actual GUI desktop

Then, I ran unity from the recovery console, it went through a few commands, got stuck at OpenGL for a few seconds, then zoomed throught many more lines of code, and ended up with this:

ERROR 2012-01-03 20.51.23 unity.launcher.Icon TrashLauncherIcon.cpp:62 Could not create file monitor for trash url: Operation not supported

* glibc detected compiz: malloc(): memory corruption: 0x09c861d6 **

After that. back at <7> : Desktop Background + Cursor

So back to the terminal again, I had to hit Ctrl+C to get back again,

now, I typed unity again, and this was the output:

WARNING: no DISPLAY variable set, setting it to :D

compiz (core) - Info: Loading plugin: core

compiz (core) - Info: Starting plugin: core

unity-panel-service: no process found

so now I did a "sudo service lightdm restart" :

X10: fatal IO error 4 (Interrupted system call) on X server ":0"

after 131 requests (130 known processed) with 0 events remaining.

lightdm stop/waiting

lightdm start/running, process 2852

Im back at the login screen, and I login again, now Im back to black screen (Yes, I lost the Desktop Background as well)

So, once again, I try unity (same response as last time):

WARNING: no DISPLAY variable set, setting it to :D

compiz (core) - Info: Loading plugin: core

compiz (core) - Info: Starting plugin: core

unity-panel-service: no process found

And still a black screen! :\

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1  
Have any active PPAs that we might need to be aware of? –  Bruno Pereira Jan 14 '13 at 10:29
    
"I checked the forums, and got various tips, none of which worked..." Why don't you concisely summarize those so that people don't "resuggest" them only to be told that that doesn't help? –  user25656 Jan 14 '13 at 10:36
    
Can you try booting using the classic DM? –  To Do Jan 14 '13 at 11:27
    
Hey Bruno... Umm, I'm not sure exactly what you might NEED to be aware of.... I've got a few repositories added, and i have apps from these that work perfectly.... However, You should know, this happened after an update... –  Pranay Prakash Jan 14 '13 at 13:17
    
@vasa1, I've gone through quite a few, I've lost track of which ones and what the tips were... Besides, I'm pretty sure even If I have seen a tip before, I must have messed it up last time, so here I can get some feedback too... –  Pranay Prakash Jan 14 '13 at 13:21

5 Answers 5

try

ctrl-alt-f2

login

type:

sudo update-grub
sudo reboot
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Just for completeness, this problem also occurs when you mistakenly installed the "nvidia-319-updates" package, but you do not have an nVidia graphics chip on your system. In my case this package was an indirect dependency from package "libopencv-dev".

So, when you're running on an ATI or Intel grpahics chip for example, and you installed openCV (package libopencv-dev), OpenGL gets broken and you'll get a black screen with mouse cursor after logging in. To resolve in this case, just remove nvidia's packages:

sudo apt-get remove nvidia-*

See this bug on launchpad for more details

share|improve this answer
    
Or a host machine with an NVIDIA card running a VM. –  Ian Mallett Apr 19 at 22:09

I had the same problem, and a shorter fix worked for me:

unity --reset

Followed by:

sudo service lightdm restart

Trouble is, you lose settings such as icon sizes, etc. These can be easily reconfigured using MyUnity or UbuntuTweak (from the software center).

(However, the problem comes back every time I connect an extra display to my laptop before booting. But that's a different problem, I presume. Discussed here: Ubuntu 12.04 Unity: Black screen with cursor only, when external display is connected before booting laptop)

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Haha, you're early! :P Nah, your solution: that's the first thing I tried. Didn't work for me though :( –  Pranay Prakash Jul 20 '13 at 22:36
    
Good to know. That means that while our symptoms are the same, the problems are not completely related. Or at least, are caused by different things. –  rudolfbyker Jul 22 '13 at 7:13
    
Well, they both do seem to be problems with unity. That's for sure! :P –  Pranay Prakash Jul 22 '13 at 9:44
up vote 3 down vote accepted

I've successfully solved the problem. Well, what I did was this:

sudo apt-get install ppa-purge
sudo ppa-purge ppa:unity-team/staging

sudo apt-get update
sudo apt-get install --reinstall ubuntu-desktop
sudo apt-get install unity

That, followed by a reboot, is the recipe for a fix! :D

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1  
Could you please ELI5 what this does? –  king_julien Sep 6 '13 at 17:38
2  
Well, this didn't work for me. –  king_julien Sep 6 '13 at 17:45

Maybe you need to reset compiz and Unity config files.

You can try a soft reset (only Unity/Compiz files, but I didn't test this): http://www.webupd8.org/2012/10/how-to-reset-compiz-and-unity-in-ubuntu.html

There's a hard reset: http://askubuntu.com/a/244064/123806

But it will erase config of some apps. Try it as a test user, go to tty1 (Ctrl+Alt+F1):

sudo adduser test

Return to tty7 (Ctrl+Alt+F7) and try login. If works, we confirm it's just a problem in your config file. Else follow the link above. (after tests, "sudo deluser test" and "sudo rm -Rf /home/test" will erase).

If Ctrl+Alt+T doesn't work...

First login and get blank screen, then Ctrl+Alt+F1, backup and remove your config file:

cp .config/dconf/user .config/dconf/user.bkp
rm .config/compiz-1/compizconfig/config .config/dconf/user

We need to remove both files at same time.

Ctrl+Alt+F7 and the expected is Unity will open.

share|improve this answer
    
Hey, thanks for the reply. However none of the methods worked. The soft reset throws a dconf bus error. The hard reset method: after making a new account, same problem there, except the desktop background shows up now as well. –  Pranay Prakash Jan 17 '13 at 16:05
    
Thanks, removing the config files worked for me (on 13.10). –  tectux Aug 21 at 12:32

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