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When my update failed going from 14.04 to 15.10, I tried formatting and doing a fresh install of 15.10

That didn't work (I'll explain now) so I tried Ubuntu-MATE 15.04 fresh install, coz I thought if I'm gonna resintall linux, might aswell try a different desktop, and maybe an older version will work. Anyway what's been happening is that when I choose ubuntu from GRUB menu, most of the time I just get a black screen with no backlight, but sometimes it boots. (And when I have the black screen I can change the volume on the keyboard and hear a sound. Strange isn't it?)

When I boot in recovery mode I found an error message that I think I managed to replicate with 

dmesg | egrep "drm|radeon"

Here is the output:

[   12.519822] [drm] Initialized drm 1.1.0 20060810
[   12.980446] [drm] VGACON disable radeon kernel modesetting.
[   12.980478] [drm:radeon_init [radeon]] *ERROR* No UMS support in radeon module!
[   13.007473] [drm] VGACON disable radeon kernel modesetting.
[   13.007502] [drm:radeon_init [radeon]] *ERROR* No UMS support in radeon module!

I have no idea what this means.

P.S, I Already tried removing the proprietary drivers, and installing the open source radeon drivers, and reinstalling the desktop and changing from lightdm to gdm incase it was lightdm not working.

mdemont
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  • What if you boot with kernel parameter nomodeset? Or boot into recovery mode and select "resume" in the menu. – Byte Commander Nov 17 '15 at 09:17
  • Thanks, Byte Commander, Booting into recovery mode seems to work. Can you tell me more about this nomodeset? Consider me a total linux newbie who just moved from Windows. – mdemont Nov 17 '15 at 13:33
  • Look at http://askubuntu.com/a/38834/367990 - the first answer by fossfreedom shows you how to set that parameter in the GRUB boot menu temporarily and the second answer by coldfish tells you how to set that permanently. Please note that it's probably not the best thing regarding performance, you may notice a strong slow-down. But it can give you a better chance to fix the real driver issues. – Byte Commander Nov 17 '15 at 13:55
  • @ByteCommander thanks for the info. Would booting from recovery mode every time save me from losing performance? Because then I wouldn't mind. – mdemont Nov 17 '15 at 15:29
  • Not really. That recovery/resume is also implicitly setting the nomodeset parameter. The final solution for this is to find a suitable driver module for your card. But just try it. If you don't feel any or much performance loss, you can of course keep your system as it is without bothering. – Byte Commander Nov 17 '15 at 16:52
  • @ByteCommander, thanks a lot for all your help. I was going nuts trying to fix this problem ;D – mdemont Nov 17 '15 at 21:41
  • Just to add information about this problem for other viewers. I do feel a huge performance loss with the nomodeset parameter and my PC gets really hot and unexpectedly turns off. @ByteCommander I looked around and I'm not even sure what a driver module is. For reference my card is "Trinity [Radeon HD 7640G]". Also I don't understand why it was working fine with an older version of ubuntu? Aren't updates supposed to make the system better? :| – mdemont Nov 20 '15 at 11:55
  • Updates bring the system up to date. That unfortunately also means that very old driver modules are removed from the HWE (hardware enablement stack), that means simply that very old cards are not natively supported any more. Maybe you should stay with 14.04 then, which is supported until 2019 or buy a newer graphics card. I unfortunately can't help you with finding a proprietary driver module that supports your card. According to http://www.notebookcheck.net/AMD-Radeon-HD-7640G.69836.0.html it was announced in 2012 though so that would not really be that old in my personal opinion... :-/ – Byte Commander Nov 20 '15 at 12:09
  • @ByteCommander yeah that's exactly what I am doing right now.. I'm just going back to 14.04, why not. Thanks again for all the help. – mdemont Nov 20 '15 at 15:54

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