[GTALUG] Headless laptop - controlling X settings

Lennart Sorensen lsorense at csclub.uwaterloo.ca
Tue Jan 26 11:10:08 UTC 2016

On Mon, Jan 25, 2016 at 08:38:00PM -0500, Giles Orr wrote:
> I have an old laptop (an Acer Travelmate 270 to be exact) that has no
> screen.  The screen busted years ago, and I simply removed it.  This
> wasn't a big problem until a couple days ago: I'd hook it up to an
> external screen via the VGA out, and everything was fine.  But a
> couple days ago, I upgraded from Debian wheezy to Debian jessie, and
> after the upgrade the external monitor now claims the provided signal
> is "Out of Range."  This doesn't appear to be the same as "No signal"
> because after several minutes it switches off (about when the screen
> blanking would kick in) and pressing a keyboard button brings back the
> "Out of Range" signal.  I can ssh into the machine, so there's an
> option to fix it.  I could potentially install Ubuntu or re-install
> wheezy, but I'd prefer to fix this if possible.  How do I tell X to
> detect and use the monitor over the external VGA connector - and only
> that connector, ignoring the now-missing internal screen candidate?
> And failing that, how can I force 1024x768 (which is what was working
> fine with wheezy) with mirroring across both outputs?
> Thanks.
> P.S. I was clever enough to try ssh with X-forwarding and then running
> arandr and eventually xrandr, but they work with the X server they can
> talk to ... which is your local machine, not the remote you've sshed
> into.  Even had that worked, I wouldn't know what settings to put into
> what file: it was bad enough back in the days of editing
> /etc/X11/Xorg.conf by hand, but it's now been replaced by a twisty
> maze of start-up scripts that are supposed to detect everything for
> you that mostly work but which have remained stubbornly opaque to me
> when they fail ...

Pointing the environment XAUTHORITY and DISPLAY at the local machine
should allow you to run xrandr remotely.

DISPLAY=:0.0 and XAUTHORITY=~/.Xauthority or maybe something in /tmp
depending on the displaymanager tends to work.

Len Sorensen

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