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I have been facing this since I changed my monitor from a CRT to LCD.

Ubuntu version: Ubuntu 9.04 kernel 2.6.28-11-generic

This is quite old machine, I am trying to access it after years - then I understood my monitor was not working - so I replaced it and then this issue started occurring.

There are two OS installed - Windows and Ubuntu. This error:

"Can not display this video mode optimum resolution 1024x768 60Hz"

occurs only for Ubuntu. Windows works perfectly fine.

I followed the following thread to resolve this issue : "Can not display this video mode" error during boot, followed by empty desktop

I faced some other difficulties while doing that as well:

  1. When I run gksu gedit /etc/default/grub, I get this error:

    gksu Gtk-WARNING **: cannot open display: :0

    I solved this by using vi (I also had to use sudo -H)

    sudo -H vi /etc/default/grub

    I observed that this was a new blank file and so I added

    GRUB_GFXMODE=640x480

    to it.

  2. After saving the file, when I tried to run sudo update-grub2 It said update-grub2 command not found. So I ran sudo update-grub and it worked fine.

I have tried these resolutions:

  • 640x480
  • 1024x768
  • 1280x800

None worked and I am still getting the same error.

Improve this question
4
  • Yeah, the lack of update-grub2 had me thinking this was either a version of Ubuntu from before 12.04 or something that wasn't Ubuntu. Rather than investing time with trying to fix this old, very unsupported version of Ubuntu, I would suggest grabbing a Live USB with 20.04 LTS or 20.10, copying any files you might want to keep, then re-installing the OS if you wish to use it.
    – user1091774
    Feb 26, 2021 at 7:45
  • What resolution did the CRT operate at, when Linux was running? Also, just to clarify, what is the actual error that you are seeing (the quotes are empty in your question, and one quote is missing in the title, so it is a bit confusing)? Is it " Can not display this video mode" or is it "Can not display this video mode optimum resolution 1024x768 60Hz"? If the latter, that would seen to be an error message from the monitor rather than Ubuntu. Please edit your question and quote the error message exactly as it appears on the screen.
    – Greenonline
    Feb 26, 2021 at 13:15
  • As the machine is an old PC, can the graphics card actually support 1024x768 at 60 Hz? If not, then it might only support 640x480 or 800x600 and so you might want to try to find an old small (14"?) LCD that runs at 640x480, and then run GRUB as it was prior to the addition of GRUB_GFXMODE=640x480. Also, what was the make/model of the CRT, as knowing that would enable us to work out which resolutions the CRT supported.
    – Greenonline
    Feb 26, 2021 at 17:00
  • 1
    Actually, its been really long that we discarded the CRT. The machine has windows too which works fine and nobody tried to use Ubuntu since many months. @Greenonline The error is "Can not display this video mode optimum resolution 1024x768 60Hz"
    – Kartiki
    Jun 11, 2021 at 11:46

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