Use Ubuntu graphical desktop without monitor at boot

Question

I have two computers: one running Windows XP and one running Ubuntu 12.04. They are connected to my monitor via a VGA switchbox. What I would like to do is be able to boot Ubuntu without a monitor, but then be able to switch back to it, and still have a graphical desktop running. I have read about creating a headless Ubuntu server, but the guides I have found all seem to involve disabling the graphical session altogether. How can I set this up?

EDIT:

My Ubuntu computer is a HP Pavilion a1120n.

Solution

Ubuntu has a great "FEATURE" (ok, it actually sucks) that disables/stops booting your system (and/or) graphical system if there is no monitor. The devs weren't smart enough to allow the system to remember the last monitor attached and/or switch to a different display automatically if you start headless and then attach a different different monitor than before.

This post will help you out (best I can do):

How to remove the graphical user interface?

Look for the answer with lots of updvotes.

You can also do this if that answer doesn't work all the way:

Create an override file for you display manager in /etc/init/ and place the word 'manual' in it. So if you have 'lightdm' you would create a 'lightdm.override' with the single word 'manual' in it, and put it in the '/etc/init/' directory. You will need to use 'sudo' to create and edit the file. Same with the grub file in the link I provided.

You can start the xserver/GUI manually:

sudo service lightdm start

and to stop it:

sudo service lightdm stop

Comments

[SirCharlo]

I just set this up with Xubuntu.. Actually, there was exactly no setup required on the Xubuntu side of things. It just works. The thing I had to change was a setting in the BIOS that, when enabled, was stopping at every boot to complain about having no screen.

[Aaron Hill]

I looked in my BIOS, and noticed a setting that controls whether the BIOS or the operating system handles Plug and Play devices necessary for boot, which was set to the operating system. Should I change this?

[SirCharlo]

To be clear, you've already tried booting with no monitor and it failed? If so, once it fails, plug in the monitor and read the error on screen. It'll help you find the cause of any underlying issue.

[Aaron Hill]

If I try to boot without a monitor plugged in, the screen will be black when I plug it in. It doesn't respond to any keys I press on the keyboard, and the Num Lock, Caps Lock, and Scroll Lock lights don't come on when I press those keys.

[ish]

Can you try switching the Grub options as in this answer: askubuntu.com/questions/161297/…

[Aaron Hill]

Thanks izk, it worked! Can you post that as an answer so that I can accept it?