I have a bootable external USB drive with Ubuntu 12 LTS, which I move between two PCs. On one machine I see the normal progression from BIOS boot device menu -> GRUB menu -> normal system splash screen. On the other one, though, I go from BIOS menu -> "No video signal" -> splash screen, that is, the monitor turns off while the GRUB menu should be displayed, and then turns back on after GRUB times out.

Can anyone suggest what's going on here, and where I should look for a solution?

Thanks, Darwin

  • Put the monitor that works on the installation that doesnt, and vice versa. If the same error occurs you have a failing Graphics adapter
    – eyoung100
    Commented Nov 8, 2015 at 3:50
  • I would, except the one that works is a laptop. Commented Nov 8, 2015 at 3:52
  • So test the monitor that isn't working by plugging it into the external VGA port on your laptop. If the montitor wakes, you have a hardware failure on the machine that isn't displaying grub
    – eyoung100
    Commented Nov 8, 2015 at 3:58
  • I'll try that later tonight. Commented Nov 8, 2015 at 3:59
  • 1
    Hmmm, that only leaves a bad resolution setting. See How do I safely change grub2 screen resolution? Skip Step 1. Set the resolution in Step 2 to 640x480, then update-grub your preferred way. If 640x480 works go up to the next known resolution, i.e. 1024x768. Keep increasing til the screen goes black then go one step backwards. Note that if 640x480 goes black, your graphics card is failing to boot in real-mode a.k.a plain VESA
    – eyoung100
    Commented Nov 23, 2015 at 3:53

1 Answer 1



The OP is having resolution problems. The issue here for me (according to comments) was that as a blank slate, I have to determine if the problem exists in the hardware or software.


After the OP ruled out hardware problems, it was easy to detemine the issue was with software, in this case GRUB2. Using the following answer:

How do I safely change grub2 screen resolution?

I advised the OP to skip Step 1, due to the fact that we cannot see the GRUB2 Console, therefore, we must manually setup a repetitive process to manually determine the highest supported resolution:

  1. Start at the lowest supported resolution. On most newer Graphics Hardware the lowest resolution is 640x480.
  2. Set the following variable in /etc/default/grub using your preferred text editor. GRUB_GFXMODE
  3. Run update-grub. Please note that the command may be different if your distribution is not Ubuntu based.
  4. Reboot
  5. Your GRUB2 menu should now be seen in 640x480
  6. Repeat steps 1 - 4, increasing the resolution from 640x480 to the point where the screen goes black. Use the well known resolutions such as 1024x768, 1280x1024, etc. You may also refer to this table: Screen Resolution Statistics, starting at the lowest resolution in the 4:3 category, and manually working towards 5:4 then 8:5 and finally 16:9.
  7. Once Steps 1 - 4 turns black again, you've reached an unsupported resolution.
  8. Repeat Steps 1 - 4 one more time, backing up one resolution.

You may want to add a comment to your grub config file so that this never happens again. To verify that you're running the maximum supported resolution you can now use the vbeinfo command, since you can now use the GRUB2 command prompt.

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