[GTALUG] Headless laptop - controlling X settings

[Mike]

On Tue, Jan 26, 2016 at 11:10 AM, Lennart Sorensen <
lsorense at csclub.uwaterloo.ca> wrote:

> 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 /etc/X11/Xorg.conf by hand, but it's now been replaced by a twisty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.
>
>
If X is indeed running on the affected monitor, and you can get remote
authority to write to the X server driving your VGA port, you might be able
to control the output using "xrandr". It might also be possible to specify
an xrandr command line for the display manager's benefit.

X.org configuration has gone largely automatic, but it should still be
possible to constrain the monitor settings without going full-tilt into
CRTC timings...
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