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Arronical
Asked: 2016-09-17 03:41:52 +0800 CST

What could prevent an Ubuntu server from booting without a VGA connected monitor?

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I've had a strange issue with an Ubuntu 14.04 server installation recently, and would like some pointers to diagnose the cause of the problem.

The OS will not boot unless a monitor is connected via the VGA port.

I believe that the boot process may be stalled at the grub menu, as the server turn off immediately when the power button is pressed, whereas power off when the OS is running takes a few seconds through the normal ACPI process.

As the OS isn't starting, there are no logs to guide me through a debugging process. What can I do to begin to understand where the problem lies?

boot

4 Answers

  1. Make a backup of /etc/default/grub and then edit the file with ...

    sudo nano /etc/default/grub

    and then find the line ...

    GRUB_CMDLINE_LINUX_DEFAULT

    and remove quiet and splash if they are there (doubt that they are cuz otherwise it would never work) and add ...

    nomodeset

    From comments for you this would be

      GRUB_CMDLINE_LINUX_DEFAULT="biosdevname=0 nomodeset"

    You will need to do a 

    sudo update-grub

    to reload grub. A reboot should let the system pass grub without a monitor.

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  2. This is quite likely a hardware issue and not related to the OS

    Many older motherboards, especially non-server ones require a connected monitor on boot during the P.O.S.T sequence otherwise the motherboard will halt during the boot sequence never reaching the boot loader.

    This often unfortunately holds true even if you enable the Don’t halt on Error option in the Bios.

    Since a small amount of current is sent through the pins to check for connectivity you can make a dummy connector by simply connecting three 50-100O Ohm resistors between the pins shown below

    enter image description here

    That's how I solved this issue with a "server" I had ;)

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  3. For HDMI you can buy a HDMI dummy plug,Headless Ghost, Display Emulator from Amazon or elewhere. HDMI Headless Plug

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  4. @Rinzwind's answer worked for me in part. I also had to uncomment GRUB_TERMINAL=console in /etc/default/grub to have a headless ubuntu server install on my system.

    Note this change made it so that my computer no longer booted with a monitor plugged in(!) Make sure your system is ssh ready before making this change.

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