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Changing the Screen Resolutions

xrandr

Supported Card Drivers

First step is just to type xrandr to see if it is supported, if xrandr is not supported check the xorg version and driver used.

To change the resolution of your primary screen assuming your card can support it, for example:

xrandr --output VGA --mode 1440x900

Dual Monitors and xrandr

xorg.conf is deprecated, if you use free drivers. If you have an xorg.conf stanza under /etc/X11/xorg.conf.d, because you use proprietary drivers for your graphics card, you should save it now before proceeding.

xorg.conf, if present at all, is now modular, for example, each module contains everything referring a "device" for instance, the display or a mouse.

With xrandr you can configure your primary and secondary screen without restarting X, (hotplug). xrandr replaces xinerama and mergedFB. With xrandr 1.2 enabled, the "old way configuration" in xorg.conf ( xinerama and mergedFB) may not work anymore.

Supported Card Drivers

Preparation for xrandr configurations of a PC with Dualhead

Note: Ideally, if you are running 2 monitors from a PC all the time, your xorg.conf should be altered to be permanently to reflect that mode.

A laptop/notebook needs to be dynamically configured (as opposed to a PC with 2 monitors) and when you reboot you will need to start over, unless you set up the dual-head with whatever parameters you use in xrandr, then you copy/paste that in a script to ~/.kde/Autostart/.

Getting familiar with xrandr

First step is just to type xrandr in a shell as user to get familiar with the output:

xrandr
Screen 0: minimum 320 x 200, current 2048 x 768, maximum 2048 x 768
VGA-0 connected 1024x768+0+0 (normal left inverted right x axis y axis) 304mm x 228mm
   1024x768       60.0*+   75.1     70.1     60.0*    59.9
   832x624        74.6
   800x600        72.2     75.0     60.3     56.2
   640x480        75.0     72.8     66.7     60.0
   720x400        70.1

Here you see that only vga, for the PC (see Appendix A for output name explanation). You see the resolutions that are supported by that screen and (which is important for dual head) the maximum screen size (here 2048x768).

Now connect your other external screen and run xrandr again:

$ xrandr
Screen 0: minimum 320 x 200, current 2048 x 768, maximum 2048 x 768
VGA-0 connected 1024x768+0+0 (normal left inverted right x axis y axis) 304mm x 228mm
   1024x768       60.0*+   75.1     70.1     60.0*    59.9
   832x624        74.6
   800x600        72.2     75.0     60.3     56.2
   640x480        75.0     72.8     66.7     60.0
   720x400        70.1
DVI-0 connected 1024x768+1024+0 (normal left inverted right x axis y axis) 310mm x 230mm
   1024x768_85.00   85.0*+
   1024x768       85.0 +   84.9     74.9     75.1     70.1     60.0     43.5
   832x624        74.6
   800x600        84.9     72.2     75.0     60.3     56.2
   640x480        84.6     75.0     72.8     66.7     60.0
   720x400        87.8     70.1
S-video disconnected (normal left inverted right x axis y axis)

Here you see that a DVI screen is connected as well, and it supports resolutions from 720x400 to 1024x768 at given refresh rates.

Configuration scenarios

Basic syntax

xrandr --output <output> --rate <rate> --mode <mode> --left-of|--right-of|--above|--below|--same-as <output>

Where:

  • <output> is output name (see Appendix A)
  • <rate> is refresh rate given by xrandr output (optional)
  • <mode> is resolution given by xrandr output (optional)
Change resolution of primary screen
xrandr --output VGA --mode 1024x768
Clone

As many external screens / video projectors do not run on 1280x800 but on e.g. 1024x768, choose this as an example:

xrandr --output VGA --mode 1024x768 --output LVDS --mode 1024x768

To turn off secondary screen and get back normal resolution on primary screen just do a:

xrandr --output VGA --off --output LVDS --mode 1280x800
Multiple display desktop

As intel GMA <=945GM/GMS looses 3d support with a virtual screen >2048x2048, you cannot put both screens next to each other in high resolution, both at 1024x768 work well:

xrandr --output LVDS --mode 1024x768 --output VGA --mode 1024x768 --left-of LVDS

To disable multi screen just disable secondary screen and change resolution of primary screen back (if needed):

xrandr --output VGA --off (--output LVDS --mode 1280x800)

Another option is to put the secondary screen above/below the primary:

xrandr --output LVDS --mode 1280x800 --output VGA --mode 1280x1024 --above LVDS

The result is a virtual screen resolution of 1280x1824 which is below 2048x2048 Another solution could be to rotate the screen:

xrandr --verbose --output LVDS --mode 1280x800 --output VGA  --mode 1024x768 --rotate left --left-of LVDS

NOTE: This only works if you can rotate your physical screen as well

Example of a permanently configured PC with dual monitors with xrandr with code snippet in /etc/X11/xorg.conf.d/30-screen.conf:
#30-screen.conf
Section "Monitor"
	Identifier      "DVI-0"
	Option          "Primary"       "true"
EndSection

Section "Monitor"
	Identifier      "DVI-1"
	Option          "RightOf"       "DVI-0"
EndSection

Section "Device"
	  Identifier     "ATI Radeon HD 2600"
	  Option         "Monitor-DVI-0" "DVI-0"
	  Option         "Monitor-DVI-1" "DVI-1"
EndSection

Note

  • Virtual screen is limited to 2048x2048 for intel, Though it's possible to set a higher virtual resolution you will loose DRI support. There does not seem to be limits for nvidia/ati.
  • TV Out does not work with ATI
  • if DDC probing does no work correctly with ATI (Xorg.0.log: (WW) RADEON(0): DDC2/I2C is not properly initialised), you might not be able to overide the values with modelines
  • When trying to setup a big desktop (dual-head) and xrandr says the resolution you're requesting is bigger than the one xrandr can support, You should use "Virtual" and the wanted resolution. (Look for the Screen Section in Apendix A)
  • For any video card, but intel, the virtual resolution should be big enough for both monitor's resolution. example: monitor1= 1024x768 and monitor2=1280x1024, then the virtual screen should be (1024+1280)x(1024>768) -> 2304x1024
Appendix A
Intel
Output names:
* LVDS: internal laptop panel
* TMDS-1: external DVI port
* VGA: external VGA port
* TV: external TV output
ATI
Output names:
* LVDS: internal laptop panel
* DVI-0: first external DVI port
* DVI-1: second external DVI port (if present)
* VGA-0: first external VGA port
* VGA-1: second external VGA port (if present)
* S-video
Nvidia
nv driver supports RandR1.2 on G80 boards
Output names:
* LVDS: internal laptop panel
* DVI0: first external DVI port
* DVI1: second external DVI port (if present)
Links

http://wiki.debian.org/XStrikeForce/HowToRandR12

http://bgoglin.livejournal.com/9846.html

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=420419

http://www.thinkwiki.org/wiki/Xorg_RandR_1.2

Dual Monitors (using binaries)

For proprietary drivers read the documentation from your graphic card manufacturer.

nvidia

Use the nvidia xorg configurator http://www.sorgonet.com/linux/nv-online/ and alter your xorg files accordingly.

Native ATI - radeon

NOTE: You will need to get the configuration information of the second monitor. To do this, you need to unplug one monitor and boot the liveCD to generate xorg.conf, copy it, then do the same with the other one.

For full configuration information see http://ftp.x.org/pub/X11R6.9.0/doc/html/radeon.4.html

Page last revised 08/01/2012 1800 UTC