xrandr

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Revision as of 02:10, 13 September 2013 by Whille (Talk | contribs) (Scripts)

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Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary wiki Template:Article summary end xrandr is an official configuration utility to the RandR X Window System extension. It can be used to set the size, orientation or reflection of the outputs for a screen. See Multihead for general informations.

Installation

Install the xorg-xrandr package from the official repositories.

Graphical frontends

There are some graphical frontends available for xrandr:

  • ARandR — Simple and convenient visual front end.
http://christian.amsuess.com/tools/arandr/ || arandr
  • LXrandR — The default monitor configuration tool for the LXDE desktop environment.
http://lxde.org/ || lxrandr

Testing configuration

When run without any option, xrandr shows the names of different outputs available on the system (LVDS, VGA-0, etc.) and resolutions available on each:

xrandr
Screen 0: minimum 320 x 200, current 1440 x 900, maximum 8192 x 8192
VGA disconnected (normal left inverted right x axis y axis)
LVDS connected (normal left inverted right x axis y axis)
   1440x900       59.9*+
   1280x854       59.9  
   1280x800       59.8  
...

You can use xrandr to set different resolution (must be present in the above list) on some output:

$ xrandr --output LVDS --mode 1280x800

When multiple refresh rates are present in the list (not in the example above), it may be changed by the --rate option, either at the same time or independently. For example:

$ xrandr --output LVDS --mode 1280x800 --rate 75
Note:
  • Changes you make using xrandr will only last through the current session.
  • xrandr has a lot more capabilities - see man xrandr for details.

Configuration

xrandr is just a simple interface to the RandR extension and has no configuration file. However, there are multiple ways of achieving persistent configuration:

  1. The RandR extension can be configured via X configuration files, see Multihead#RandR for details. This method provides only static configuration.
  2. If you need dynamic configuration, you need to execute xrandr commands each time X server starts. See Execute commands after X start for details. This method has the disadvantage of occurring fairly late in the startup process, thus it will not alter the resolution of the Display Manager if you use one.
  3. Custom scripts calling xrandr can be bound to events (for example when external monitor is plugged in), see acpid for details. The #Scripts section provides you with some example scripts that might be useful for this purpose.
Tip: Both KDM and GDM have startup scripts that are executed when X is initiated. For GDM, these are in /etc/gdm/, while for KDM this is done at /usr/share/config/kdm/Xsetup. This method requires root access and mucking around in system config files, but will take effect earlier in the startup process than using xprofile.

Scripts

Example 1

This script toggles between external monitor (specified by $EXT) and default monitor (specified by $IN), so that only one monitor is active at a time.

The default monitor (specified by $IN) should be connected when running the script, which is always true for a laptop.

#!/bin/bash

IN="LVDS1"
EXT="VGA1"

if (xrandr | grep "$EXT disconnected"); then
    xrandr --output $EXT --off --output $IN --auto
else
    xrandr --output $IN --off --output $EXT --auto
fi

Example 2

This script toggles only external monitor (specified by $EXT), leaves the default monitor (specified by $IN) on.

The default monitor (specified by $IN) should be connected when running the script, which is always true for a laptop.

#!/bin/bash

IN="LVDS1"
EXT="VGA1"

if (xrandr | grep "$EXT disconnected"); then
    xrandr --output $IN --auto --output $EXT --off 
else
    xrandr --output $IN --auto --primary --output $EXT --auto --right-of $IN
fi

Example 3

This script iterates through connected monitors, selects currently active (primary) monitor, turns next one on and the others off:

# get info from xrandr
connectedOutputs=$(xrandr | grep " connected" | sed -e "s/\([A-Z0-9]\+\) connected.*/\1/")
activeOutput=$(xrandr | grep -e " connected [^(]" | sed -e "s/\([A-Z0-9]\+\) connected.*/\1/") 
connected=$(echo $connectedOutputs | wc -w)

# initialize variables
execute="xrandr "
default="xrandr "
i=1
switch=0

for display in $connectedOutputs
do
	# build default configuration
	if [ $i -eq 1 ]
	then
		default=$default"--output $display --auto "
	else
		default=$default"--output $display --off "
	fi

	# build "switching" configuration
	if [ $switch -eq 1 ]
	then
		execute=$execute"--output $display --auto "
		switch=0
	else
		execute=$execute"--output $display --off "
	fi

	# check whether the next output should be switched on
	if [ $display = $activeOutput ]
	then
		switch=1
	fi

	i=$(( $i + 1 ))
done

# check if the default setup needs to be executed then run it
echo "Resulting Configuration:"
if [ -z "$(echo $execute | grep "auto")" ]
then
	echo "Command: $default"
	`$default`
else
	echo "Command: $execute"
	`$execute`
fi
echo -e "\n$(xrandr)"


Example 4 - auto set screen size of monitor

This scrip auto set best screen size, for example, if a laptop connected to monitors with different size, 1440, 1920, ...

xrandr --output VGA1 --off && xrandr --auto

change VGA1 to other type, say HDMI1 if needed.

Using xrandr with VNC

Tango-view-refresh-red.pngThis article or section is out of date.Tango-view-refresh-red.png

Reason: the -s option is for version 1.1 (Discuss in Talk:Xrandr#)

Tango-edit-clear.pngThis article or section needs language, wiki syntax or style improvements.Tango-edit-clear.png

Reason: duplicates #Adding undetected resolutions (Discuss in Talk:Xrandr#)

If you are using a VNC server that supports xrandr, you can change the vnc resolution on the fly, for example by running xrandr -s 1920x1200. tigervnc is an example of a client that supports xrandr.

If you run xrandr from a VNC session, you will get a list of currently configured modes. Each of these modes can be activated with the xrandr -s <width>x<height> command; however, if the mode you want does not exist in the list, you must first add it. As an example, we will add resolution 1024x600:

First run cvt to get the correct modeline for the resolution you want to add:

$ cvt 1024 600
# 1024x600 59.85 Hz (CVT) hsync: 37.35 kHz; pclk: 49.00 MHz
Modeline "1024x600_60.00"   49.00  1024 1072 1168 1312  600 603 613 624 -hsync +vsync

Use that modeline output to run the commands below:

$ xrandr --newmode "1024x600"   49.00  1024 1072 1168 1312  600 603 613 624 -hsync +vsync
$ xrandr --addmode default "1024x600"

Doing the above will give you the ability to change to 1024x600 by running xrandr -s 1024x600, but it will only last for the current x session. To ensure that you can use the newly added resolution each time you start vncserver, add the above commands to ~/.vnc/xstartup.

Troubleshooting

Adding undetected resolutions

Due to buggy hardware or drivers, your monitor's correct resolutions may not always be detected by xrandr. For example, the EDID data block queried from the monitor may be incorrect. However, we can add the desired resolutions to xrandr.

First we run gtf or cvt to get the Modeline for the resolution we want:

For some LCD screens (samsung 2343NW), the command "cvt -r" (= with reduced blanking) is to be used.

$ cvt 1280 1024
# 1280x1024 59.89 Hz (CVT 1.31M4) hsync: 63.67 kHz; pclk: 109.00 MHz
Modeline "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync
Note: If the Intel video driver xf86-video-intel is used, it may report the desired resolution along with its properties in /var/log/Xorg.0.log — use that first if it is different from the output of gtf or cvt. For instance, the log and its use with xrandr:
[    45.063] (II) intel(0): clock: 241.5 MHz   Image Size:  597 x 336 mm
[    45.063] (II) intel(0): h_active: 2560  h_sync: 2600  h_sync_end 2632 h_blank_end 2720 h_border: 0
[    45.063] (II) intel(0): v_active: 1440  v_sync: 1443  v_sync_end 1448 v_blanking: 1481 v_border: 0
xrandr --newmode "2560x1440" 241.50 2560 2600 2632 2720 1440 1443 1448 1481 -hsync +vsync

Then we create a new xrandr mode. Note that the Modeline keyword needs to be ommited.

$ xrandr --newmode "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync

After creating it we need an extra step to add this new mode to our current output (VGA1). We use just the name of the mode, since the parameters have been set previously.

$ xrandr --addmode VGA1 1280x1024_60.00

Now we change the resolution of the screen to the one we just added:

$ xrandr --output VGA1 --mode 1280x1024_60.00

Note that these settings only take effect during this session.

If you are not sure about the resolution you will test, you may add a sleep 5 and a safe resolution command line following, like this :

$ xrandr --output VGA1 --mode 1280x1024_60.00 && sleep 5 && xrandr --newmode "1024x768-safe" 65.00 1024 1048 1184 1344 768 771 777 806 -HSync -VSync && xrandr --addmode VGA1 1024x768-safe && xrandr --output VGA1 --mode 1024x768-safe

Also, change VGA1 to corret output name.

Resolution lower than expected

Tip: Try #Adding undetected resolutions first, if it doesn't work, you may try this method.

If you video card is recognized but the resolution is lower than you expect, you may try this.

Background: ATI X1550 based video card and two LCD monitors DELL 2408(up to 1920x1200) and Samsung 206BW(up to 1680x1050). Upon first login after installation, the resolution default to 1152x864. xrandr does not list any resolution higher than 1152x864. You may want to try editing /etc/X11/xorg.conf, add a section about virtual screen, logout, login and see if this helps. If not then read on.

Change xorg.conf

/etc/X11/xorg.conf
Section "Screen"
        ...
        SubSection "Display"
                Virtual 3600 1200
        EndSubSection
EndSection

About the numbers: DELL on the left and Samsung on the right. So the virtual width is of sum of both LCD width 3600=1920+1680; Height then is figured as the max of them, which is max(1200,1050)=1200. If you put one LCD above the other, use this calculation instead: (max(width1, width2), height1+height2).

See also