Dual screen support?

[NickC]

Another minor problem I have is that of configuring dual screens. Having done a basic install I find that both monitors work but are simply mirrored, I can't figure out how to configure them as one continual desktop. GPU is nVidia.

Thanks

[Shador]

If you have the proprietary nvidia driver installed just run "NVIDIA X Server Settings" from the application menu.
For nouveau you need to add a file to the /etc/X11/xorg.conf.d directory with a content similar to this:

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Section "Monitor"
	Identifier "DVI-I-1"
	Option "Primary" "true"
	Option "Enabled" "true"
EndSection

Section "Monitor"
	Identifier "VGA-1"
	Option "RightOf" "DVI-I-1"
	Option "Enabled" "true"
EndSection

Run the xrandr command for a list of available outputs. This is for example the output on my laptop

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Screen 0: minimum 320 x 200, current 1280 x 800, maximum 4096 x 4096
VGA1 disconnected (normal left inverted right x axis y axis)
LVDS1 connected 1280x800+0+0 (normal left inverted right x axis y axis) 331mm x 207mm
   1280x800       60.0*+
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
TV1 disconnected (normal left inverted right x axis y axis)

VGA1 is the identifier of the external display which is not connected as you can see. LVDS1 is the one of the internal screen. Depending on your hardware you'll get different identifiers.

After changing the settings be sure to reboot. While the NVIDIA tool applies changes instantly, this allows you to check whether everything is right.

[NickC]

Thanks Shador,

Does it matter what that file is called?

I have created the following /etc/X11/xorg.conf.d/dualmon

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Section "Monitor"
   Identifier "DP-1"
   Option "Primary" "true"
   Option "Enabled" "true"
EndSection

Section "Monitor"
   Identifier "DP-2"
   Option "RightOf" "DP-2"
   Option "Enabled" "true"
EndSection

Where DP-1 & DP-2 are the monitors names from xrandr.

Rebooted but no change, screens still mirrored.

[NickC]

Found the last piece of the jigsaw, needed to name the file 10-monitor.conf. Dual screens now working correctly. Shame there isn't a graphical tool for doing this but this works.

Thanks,

[Shador]

There are, but changes are not reflected to your xorg.conf. Thus they only affect your desktop session, i.e. not login screen or your de's splash screen.

I guess the problem is that depending on the driver the xorg configuration looks different, especially for the proprietary nvidia drivers, which have their own very weird way of doing things. It's also quite dependent on the distro/version of Xorg you're running. The only unified interface available is randr but that's not persistent and must be invoked every time you login, which causes the aformentioned problem with login screen and splash.

[thenktor]

Found the last piece of the jigsaw, needed to name the file 10-monitor.conf.

All active files in /etc/X11/xorg.conf.d/ need the extension ".conf". You can simply deactivate a config if you rename it to e.g. ".off".

[NickC]

There are, but changes are not reflected to your xorg.conf. Thus they only affect your desktop session, i.e. not login screen or your de's splash screen.

Where do I find these graphical tool for doing this, the fact that they only affect my desktop session is not a problem.

[gapan]

Xfce and KDE have their own tools and they are already installed and waiting for you in the menu. LXDE and Fluxbox have lxrandr which does exactly the same. Also already installed.

[NickC]

Xfce and KDE have their own tools and they are already installed and waiting for you in the menu. LXDE and Fluxbox have lxrandr which does exactly the same. Also already installed.

In that case can anyone tell me where I find this tool in the Xfce environment? When I looked in settings -> display there was only one screen available and therefore no option to stop the two screens being mirrored.

[gapan]

That's the one. If only one screen shows up in there, then something else is wrong. What is the output of

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xrandr

?