Hi,
I'm running Debian Squeeze on a semi-ancient Acer Aspire 5920G, having recently moved from Fedora. One of the issues that I've been struggling with is that whenever I plug in an external monitor, and then try to switch monitors (by pressing Fn+F5 in my case), the laptop monitor goes black. It doesn't seem to just be the case of the monitor because using keybindings to access the terminal, typing sudo reboot followed by my password doesn't work either (obviously this is all done in the dark, but after n attempts it becomes quite clear that it's not working). I thought that maybe Debian had bound my Fn+F5 combo to something else, but entering the monitor settings and manually "enabling" the external monitor triggers the same effect. I first thought that maybe this was the consequence of me mucking about with the proprietary video drivers, but I'm currently running the free ones and the problem persists.

Any thoughts on this would be splendid, as whenever I hit the Fn+F5 combo I always have to do a hard reboot whenever the monitor turns off, so it takes some time to go through a process of trial and error!

Cheers,
Sid

When I switch to an external, pressing the Fn key once switches to external; pressing it again turns on both; pressing it a third time turns off the external. This seems to built into the laptop itself, as it does this with several OS's.

I'm just guessing, but it could be that your laptop is too old have have that middle step. It might be worth a look at the BIOS in case it tells you something.

1 members found this post helpful.

Nah, I've used an external monitor on it for Windows, Ubuntu and Fedora; it's only with Debian that there's been an issue. The problem seems to be slightly attenuated once I disabled KMS (/etc/modprobe.d/i915-kms.conf - value changed from 1 to 0); I still can't hibernate - the laptop monitor will flash on and off with nonsense graphics (just seemingly random stripes), and I have to do a hard reboot. However, I can suspend it as well as plug in a monitor now, so all is well. Thought I'd put that on here for any future googlers. Also, if anyone happens to come across this post and knows why disabling KMS fixed both the suspend and monitor plugin bit, I'd be very happy to know why this is the case. Not too worried about the hibernate bit, but if anyone has a solution that as well, I'll be more than grateful to hear it.

Well it was a shot in the dark.

What video does it have? Perhaps it's running on a generic driver and needs a more specific one. Debian is aggressively non-free; some proprietary non-free drivers that other distros include by default need to be sought specifically for Debian.

http://www.pcworld.com/businesscente..._licenses.html

I have the acer aspire 3620 with the i915 drivers which is not well supported anymore not even for wins.
When I connect the external monitor, I would actually be happy if my monitor shut off beccause with the 2 running the video is very sluggish if it doesn't freeze up when playing movies.
Now that I see the solution frankbell offered I may try shutting down the monitor to watch movies on a bigger monitor. But all in all both monitors would work with debian.