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I'm running Ubuntu 14.04 on a DELL R320. I have no 3rd party drivers enabled. Machine boots normally, but when the login screen loads, it flashes momentarily and disappears and the monitor says "Input not supported". When I was building the machine, I've set the desktop at 1024x768 which is definitely supported by the monitor I'm using.

I've tried modifying /etc/default/grub to set GRUB_GFXMODE=1024x768 (and running update-grub after), with no change.

Firstly, is there some log files I can check to try to figure out what's going wrong?

This is new territory for me, and I've read a bit about X.org... should I be changing anything there?

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is it GRUB_GFXMODE=1024x768 or #GRUB_GFXMODE=1024x768 ? –  JoKeR Jun 3 '14 at 15:06
did you also try to input 800x600 just to check. –  JoKeR Jun 3 '14 at 15:10
Yes, the line is uncommented. I've tried 1024x768, 800x600, and 640x480, all with the same result. (Boot display is OK, but disappears as soon as login screen shows). I luckily can still SSH in from another machine (allowing for these config changes). It's almost like there's a resolution change happening when the login screen loads... is that still controlled by GRUB? Or does GRUB stop when the desktop GUI loads? –  PanicRev Jun 3 '14 at 16:36
could you please add the output lspci -nnk | grep -iA2 VGA I'd like to know if you're using the proprietary driver, this command will show you your structure and what kernel driver for video is active. –  JoKeR Jun 4 '14 at 18:02
all logs are kept in /var/log for example var/log/Xorg.log.0 –  JoKeR Jun 4 '14 at 18:14

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