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Suppose I have a Linux Xen machine with multiple graphics adapters + an onboard graphics adaptor.

Suppose they are all PCIe adapters.

I am guessing that the Linux kernel decides to use whichever graphics adapter it finds first to use as it's VGA output when booting?

Is there a way to direct this output to a specific adapter through a kernel boot option?

Reason: I'm wanting to keep onboard graphics as the console output for Linux (it is ubuntu server - not running X). The other graphics adaptors will be passed through to multiple Xen guests.

Note: It doesn't make any difference as to whether a monitor or dummy VGA plug is attached. Linux grabs one of the cards regardless of the state of any connected device. What I'm wanting to do is to tell the kernel I want you to use the adaptor at xx:xx.0 pci address or something.

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On second thought, I think this may be controlled by the BIOS –  Matt Sep 5 '11 at 10:28
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2 Answers

up vote 1 down vote accepted

Usually, you should be able to select a 'BOOT VGA' in the BIOS, there you should be able to select 'onboard' or 'external'.

Usually linux should use the VGA adapter selected by the BIOS as the default.

The other cards can then be used by running Xorg on them later

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Ya I've had a similar problem to this. You may not like the solution, but I swear it worked for me!!

In my case I ended up using a hardware VGA plug with 3 resistors. I made it by cutting a standard vga cable about 1.5 inches from one end of the cable. Then I stripped out the wires and soldered on 75 ohm resistors across the correct wires. After testing the ohms with a meter I globed hot glue over the whole thing. I don't have a picture but it's pretty simple.

Here are 2 guides that cover this procedure:

http://soerennielsen.dk/mod/VGAdummy/index_en.php

http://www.geeks3d.com/20091230/vga-hack-how-to-make-a-vga-dummy-plug/

Finally, I remember some random post about certain motherboards having an option for this in the BIOS...mine did not.

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Thanks, but that's not quite what I was after. I'll edit my question. –  Matt Aug 31 '11 at 0:25
    
Please don't sign your posts (your sig block gets added automatically anyway) and please stop posting links to your podcast site. The content may be excellent (I don't know, I've never listened), but it's still unsolicited self-promotion a.k.a. spam. Don't do it. If you want to advertise here, you can pay for it like the rest of the advertisers do. –  EEAA Nov 15 '11 at 6:22
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