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I have a computer that has no monitor attached to it.

When I boot the system, X fails to start because there is no monitor detected. If I boot it with a monitor attached and after X has started, when I remove the monitor everything works fine.

Details and Background:

This computer is a kind of hardware consolidation server. It's only purpose is to run two Virtual Box VM's that run Windows XP and some important but seldom used (once or twice a month) programs. For a couple of time it has been lying in a corner with an old monitor attached to it and working great.

But space in the office was getting scarce and I moved the computer to the server room. There is no monitor attached to it there (no space), and sometimes the computer is rebooted. When it boots without monitor X is not started, the vms doesn't start and I get called to solve the problem.

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up vote 4 down vote accepted

According to this tread a possible solution for 10.04 may be to both

  • define a standard xorg.conf, and
  • prevent KMS at boot.

However solution #13 there with resistors plugged to the vga port for fake monitor is really funky.

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OMG... I have a couple of spare DVI-VGA adapters and some resistors here... and the computer video card has both VGA and DVI port. Something inside my loves to try that solution ;). – Javier Rivera Feb 16 '11 at 11:43
+1 for solution #13 – djeikyb Feb 16 '11 at 11:44
Ok, this solves the problem. No, not #13, the boring way: custom xorg.conf and disabling KMS. This is the xorg.conf that I used: , it's the same as #21 in the forum post, but using the radeon driver instead of vesa. – Javier Rivera Feb 16 '11 at 13:57

I think it's because Xorg nowdays are designed to run without a config file, that is: some kind of auto-detection. For sure, it has the "problem" that it cannot detect your monitor if it's not there ... What I would do is to create a config file for Xorg server, so you have "hard coded" config then, no need for auto detection.

Run this command from a text VT as root:

sudo Xorg -configure

It will create a config file for you, if I remember well with name something like in your home directory. Move/copy it as /etc/X11/xorg.conf, also you may need to customize it a bit. If X works properly with that configuration (try that with a monitor attached first, of course), you can try it out what happens if you remove the monitor.

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I'll try this as soon as possible and keep you updated. – Javier Rivera Feb 16 '11 at 11:41
Ah, and the other answer you got here is important: KMS can be a problem, I haven't mentioned it, since I don't use KMS, I have only machines with nvidia cards where I use nvidia's driver ... – LGB Feb 16 '11 at 12:55
Didn't work. Xorg -configure just hang the computer. It's using the radeon driver. – Javier Rivera Feb 16 '11 at 13:22
It shouldn't hang ... What way did it hang exactly? Maybe you can also check the xorg log file out in /var/log to see what happened. – LGB Feb 17 '11 at 8:44

Check out IgnoreEDID.

Option "IgnoreEDID" "TRUE"
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Where in the Xorg config should this be placed? – gertvdijk Jul 22 '13 at 11:05

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