When I used Windows 7 on the same PC, I didn't have this problem. Now I can't start my server if monitor is not connected. When I turn it on without monitor, I can't hear HDD loading and also can't connect via SSH. I tried to add nomodeset to my /etc/default/grub, and then grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg, but it doesn't fix anything. Booting with keyboard doesn't work, monitor is a rootcause.

What can I do?

  • What is displayed when you connect the monitor after it has failed to boot?
    – Fabby
    Feb 17 '19 at 14:02
  • when i connect monitor after boot, monitor doesn't show anything at all, i thing its a bug of hdmi
    – stiv
    Feb 17 '19 at 14:08
  • Try booting it with just a keyboard attached, does it boot? Feb 17 '19 at 14:24
  • Did you update the firmware between upgrading from W7 to CentOS?
    – Fabby
    Feb 17 '19 at 14:36
  • no, hardware and bios are the same absolutely
    – stiv
    Feb 17 '19 at 14:43

You could try these dummy plugs as options:


  • HW problem, HW solution: +1 although technically off topic.
    – Fabby
    Feb 17 '19 at 15:42
  • This is software problem, because Windows7 works correctly on same hardware.
    – stiv
    Feb 17 '19 at 16:13
  • Windows talks directly to the BIOS these days and does things to make using it easier, without notifying the user what it did. So there is no telling what it did or is doing. Feb 18 '19 at 4:25

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