[Novalug] two monitors on the same box

Nino R. Pereira ninorpereira@gmail.com
Sat Nov 26 14:39:52 EST 2011


Hi,

one of the issues I got some good input on at the last Saturday meeting
was how to get two monitors on the same box.

I now have two of them connected, one 22 inch, the other 24 inch. The
22 inch is connected to the older type video output plug, with 3 rows
of round pins and maybe 25 in total, the 24 inch one through the more modern
plug with lots of small rectangular plugs, with three orientations
(these plugs must have names, but I don't know those).

Both monitors show the same image. When I go to

system > preferences > monitors

I see a GUI called 'Monitor Preferences' that shows a pink 'Mirror Screens'
inside a brownish plane. There's a tick box that says 'Same image in all 
monitors'.
When I untick this, I get the two monitors individually, the 22" one 
pink with a
bluish border, the 24" one green without a border. I click on the green one,
and I get a border but otherwise nothing changes.

I see the resolution: the 22" one is 1680x1050, the 24" one is 1920x1200.
I can keep these on, or click them off. Then, the respective panel
becomes black but otherwise nothing happens: I didn't select 'Apply' 
just yet.

This is where the problem is: when I select 'Apply', it asks me politely
that 'the virtual resolution must be set in your configuration file in order
to apply your settings", and it recommends that I do that. So I say 'yes'.
I'm told that this requires privileges, and I'm asked for the superuser's
password.

Now, I normally use 'sudo' so this would be my normal password. But, there's
also the superuser password, which I can check is correct by doing 'su'.
I try both passwords, neither works.

I've also tried to type 'xrandr' and looked at the options, but
those are a little scary. Since I don't want to end up with a black
monitor I didn't exercise this one. 'xrandr' knows about the monitors,
because it gives

VGA-0 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 
474mm x 296mm
and
DVI-0 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 
518mm x 324mm

where the old connector is apparently 'VGA-0' and the new connector 
apparently 'DVI-0:
the latter is not working at its recommended resolution, but it doesn't 
tell you
how to correct the problem.

Can anyone tell me what the problem might be? Is there a file that this
program looks at before it can find the password?

Thank you,

Nino





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