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<h1><a href="../index.html">XSF</a> / How to use xrandr</h1>
<span id="author">Cyril Brulebois</span><br />
<span id="email"><code><<a href="mailto:kibi@debian.org">kibi@debian.org</a>></code></span><br />
<div id="toc">
<div id="toctitle">Table of Contents</div>
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</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_getting_started">Getting started</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_what_is_xrandr">What is xrandr?</h3>
<div class="paragraph"><p><code>xrandr</code> is a command-line tool to interact with the X <code>RandR</code>
extension [see <a href="https://www.x.org/wiki/Projects/XRandR">x.org</a>,
<a href="https://en.wikipedia.org/wiki/RandR">wikipedia</a>], which allows for
live (re)configuration of the X server (<em>i.e.</em> without restarting it):
It provides automatic discovery of modes (resolutions, refresh rates,
etc.) together with the ability to configure outputs dynamically
(resize, rotate, move, etc.).</p></div>
<div class="paragraph"><p><strong>FIXME: Status across drivers?</strong></p></div>
</div>
<div class="sect2">
<h3 id="_what_consequences_for_xorg_conf">What consequences for xorg.conf?</h3>
<div class="paragraph"><p>Starting with <code>squeeze</code>, removing the <code>xorg.conf</code> configuration file
entirely should work well enough, but in case that doesn’t work out,
let’s document what can be removed from it from a <code>RandR</code> point of
view.</p></div>
<div class="paragraph"><p>With the driver detecting modes automatically, several configuration
options become useless most of the time in your configuration file
(xorg.conf). You might want to remove:</p></div>
<div class="ulist"><ul>
<li>
<p>
<code>HorizSync</code> and <code>VertRefresh</code> from the <code>Monitor</code> section.
</p>
</li>
<li>
<p>
Modes from <code>Display</code> subsection in <code>Screen</code> section.
</p>
</li>
<li>
<p>
<code>ModeLine</code> from the <code>Monitor</code> section.
</p>
</li>
</ul></div>
<div class="paragraph"><p>There’s also no need to keep static dual-head configuration. Some
suggestions to get a tiny <code>xorg.conf</code>:</p></div>
<div class="ulist"><ul>
<li>
<p>
Drop dual <code>Device</code>/<code>Screen</code>/<code>Monitor</code> sections, a single one is
needed.
</p>
</li>
<li>
<p>
Drop <code>MonitorLayout</code> option and <code>Screen</code> lines from the remaining
<code>Device</code> section.
</p>
</li>
<li>
<p>
Drop the <code>ServerLayout</code> section(s).
</p>
</li>
<li>
<p>
Drop <code>RightOf</code>/<code>LeftOf</code> indication of the remaining <code>Screen</code> line
in <code>ServerLayout</code> section.
</p>
</li>
</ul></div>
<div style="page-break-after:always"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_basic_xrandr_usage">Basic xrandr usage</h2>
<div class="sectionbody">
<div class="paragraph"><p>Once the configuration file (<code>xorg.conf</code>) is removed or updated,
starting the server should enable some outputs by default. Their
top-left corners will be at the same part of the image, but their
modes will probably be different.</p></div>
<div class="paragraph"><p>All outputs may be configured through <code>xrandr</code>. To see the available
outputs, just run <code>xrandr</code>:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr
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 inverted X and Y axis (normal left inverted right x axis y axis) 261mm x 163mm
1280x800 59.8*+
1024x768 60.0
800x600 60.3 56.2
640x480 59.9
DVI1 disconnected (normal left inverted right x axis y axis)
TV1 disconnected (normal left inverted right x axis y axis)</code></pre>
</div></div>
<div class="paragraph"><p>Comments:</p></div>
<div class="ulist"><ul>
<li>
<p>
We see 4 outputs: <code>VGA1</code>, <code>LVDS1</code>, <code>DVI1</code>, <code>TV1</code>.
</p>
</li>
<li>
<p>
Only the internal panel (<code>LVDS1</code>) is connected and it supports 4
modes at 60 Hz, 1 mode at 56 Hz.
</p>
</li>
<li>
<p>
The mode marked with a star (<code>*</code>) is the current mode.
</p>
</li>
<li>
<p>
The one marked with a plus (<code>+</code>) is the preferred one. Most
monitors report a preferred mode to the driver. And the
server/driver will generally choose it by default.
</p>
</li>
</ul></div>
<div class="paragraph"><p><strong>FIXME: Mention output name conventions?</strong></p></div>
<div class="paragraph"><p>When manipulating <code>VGA1</code> output properties, you should use:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --output VGA1 <options></code></pre>
</div></div>
<div class="sect2">
<h3 id="_adding_removing_heads_dynamically">Adding/removing heads dynamically</h3>
<div class="paragraph"><p>The old days where you had to restart X when plugging a new monitor
are gone. With <code>RandR</code> 1.2, you can plug/unplug monitors whenever you
want. Running the following line will query all outputs and enable
them with their default mode:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --auto</code></pre>
</div></div>
<div class="paragraph"><p>You may also disable one output using:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --output LVDS1 --off</code></pre>
</div></div>
<div class="paragraph"><p>This may be useful for some buggy application that don’t support
multiple outputs well. Also, due to CRTC limitations (see the Caveats
section below), it is often required to disable one output before
enabling another since most hardware only support 2 at the same time.</p></div>
</div>
<div class="sect2">
<h3 id="_changing_the_mode">Changing the mode</h3>
<div class="paragraph"><p>With the above <code>xrandr</code> output, you may change the <code>LVDS1</code> mode to
<code>1024x768</code> using:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --output LVDS1 --mode 1024x768</code></pre>
</div></div>
<div class="paragraph"><p>The refresh rate may also be changed, either at the same time or
independently:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --output LVDS1 --mode 1024x768 --rate 75
$ xrandr --output LVDS1 --rate 75</code></pre>
</div></div>
<div class="paragraph"><p>To get back to the default mode:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --output LVDS1 --auto</code></pre>
</div></div>
<div style="page-break-after:always"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_placing_outputs_in_a_virtual_screen">Placing outputs in a virtual screen</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_a_bit_of_configuration_for_non_kms_setups">A bit of configuration for non-KMS setups:</h3>
<div class="paragraph"><p>Let’s have a look at the maximal virtual screen size, we see
<code>4096x4096</code> in this example:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr|head -1
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 4096 x 4096</code></pre>
</div></div>
<div class="paragraph"><p>With KMS (<strong>FIXME: Link to a page which explains what KMS is</strong>),
there’s no need to specify any <code>Virtual</code> option. With DRI and without
KMS, that might be needed. Indeed, drivers will often create a default
virtual screen with small dimensions, for instance <code>1600x1200</code>, to
reduce memory consumption.</p></div>
<div class="paragraph"><p>If you plan to use multiple outputs displaying different zones, you
should configure your <code>xorg.conf</code> by adding a <code>Virtual</code> line to the
<code>Display</code> subsection in the <code>Screen</code> section.</p></div>
<div class="listingblock">
<div class="content">
<pre><code>Section "Screen"
…
SubSection "Display"
Depth 24
Virtual 3000 2000
EndSubSection
EndSection</code></pre>
</div></div>
</div>
<div class="sect2">
<h3 id="_place_outputs">Place outputs</h3>
<div class="paragraph"><p>Outputs are placed using the following options:
<code>--right-of</code>/<code>--left-of</code>/<code>--above</code>/<code>--below</code>. For instance, to place
the <code>VGA1</code> output virtually-right of the internal panel (<code>LVDS1</code>):</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --output VGA1 --right-of LVDS1</code></pre>
</div></div>
<div class="paragraph"><p>Note that hardware and memory limitations may severely restrict the
size of your virtual screen, see the Caveats section below.</p></div>
<div style="page-break-after:always"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_adding_new_modes">Adding new modes</h2>
<div class="sectionbody">
<div class="paragraph"><p>Under some circumstances, some modes might be missing. For instance,
if the monitor does not report correct EDID information. Or if the
output didn’t have a CRTC available at startup because another output
was using it and you disabled it in the meantime.</p></div>
<div class="paragraph"><p>If a mode exist, you may add it to one output with:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --addmode VGA1 800x600</code></pre>
</div></div>
<div class="paragraph"><p>If the mode does not exist, you may first create it by passing a modeline:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ xrandr --newmode <ModeLine></code></pre>
</div></div>
<div class="paragraph"><p>You may create a modeline using the <code>gtf</code> or <code>cvt</code> tools (shipped in
the <code>xserver-xorg-core</code> package).</p></div>
</div>
</div>
</div>
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Last updated
2020-10-09 09:18:55 UTC
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