path: root/docs/man/kmscon.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
          "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  Written 2012 by David Herrmann <dh.herrmann@googlemail.com>
  Dedicated to the Public Domain
-->

<refentry id="kmscon">
  <refentryinfo>
    <title>kmscon</title>
    <productname>kmscon</productname>
    <date>December 2012</date>
    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>David</firstname>
        <surname>Herrmann</surname>
        <email>dh.herrmann@googlemail.com</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>kmscon</refentrytitle>
    <manvolnum>1</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>kmscon</refname>
    <refpurpose>KMS/DRM based System Console</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>kmscon <arg choice="opt" rep="repeat">OPTIONS</arg></command>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>kmscon -l <arg choice="opt" rep="repeat">OPTIONS</arg> -- /bin/login <arg choice="opt" rep="repeat">/bin/login-OPTIONS</arg></command>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>
    <para>kmscon is a KMS/DRM-based system console with an integrated terminal
          emulator for linux operating systems. It was designed as a replacement
          for the linux kernel console and virtual terminals.</para>

    <para>When run in default mode, kmscon allocates a virtual terminal and
          provides a terminal emulator on it. It can thus be used as replacement
          for the linux console and
          <citerefentry><refentrytitle>agetty</refentrytitle><manvolnum>1</manvolnum></citerefentry>
          on virtual terminals.
          Compared to the linux console, kmscon provides a rich set of enhanced
          features including full internationalized keyboard support, full UTF-8
          input/font support, hardware-accelerated rendering, multi-seat
          support and more.</para>

    <para>When run in listener mode, kmscon watches the system for new seats and
          automatically provides a system console on it.</para>

    <para>Default configuration directory is <filename>/etc/kmscon/</filename>
          and the main configuration file is called
          <filename>/etc/kmscon/kmscon.conf</filename>. You can provide an
          additional configuration file for each seat via
          <filename>/etc/kmscon/{seatname}.kmscon.conf</filename>.
          Any command-line option that can be passed to kmscon can also be put
          into those configuration files. Command-line options overwrite
          configuration file options. And per-seat configuration files overwrite
          the global configuration file.</para>
  </refsect1>

  <refsect1>
    <title>Options</title>
    <para>Boolean options take no arguments. If the default value is true, then
          you can disable the option by prefixing it with
          <emphasis>no-</emphasis>.</para>

    <para>General Options:</para>

    <variablelist>
      <varlistentry>
        <term><option>-h</option></term>
        <term><option>--help</option></term>
        <listitem>
          <para>Prints a short help text and exits. (default: off)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-v</option></term>
        <term><option>--verbose</option></term>
        <listitem>
          <para>Be more verbose. (default: off)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--debug</option></term>
        <listitem>
          <para>Print debug messages. Works only if kmscon was compiled with
                debug mode enabled. (default: off)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--silent</option></term>
        <listitem>
          <para>Suppress notices and warnings. (default: off)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--configdir {/path/to/config/dir/}</option></term>
        <listitem>
          <para>Specify path to config directory. (default: /etc/kmscon/)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--listen</option></term>
        <listitem>
          <para>Run kmscon in listen-mode. See section below for more
                information. (default: off)</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Seat Options:</para>

    <variablelist>
      <varlistentry>
        <term><option>--vt {/path/to/vt}</option></term>
        <listitem>
          <para>Use this VT. If not specified, kmscon tries to find a VT by
                itself. On seats without VTs, kmscon simply activates itself
                automatically without using any VT. Please note that you cannot
                use this option if kmscon runs on multiple seats
                (see <option>--seats</option>). To avoid this, specify this
                option in a seat configuration
                <filename>/etc/kmscon/{seat}.kmscon.conf</filename>.</para>
          <para>You must not run multiple applications on a single VT,
                otherwise, you might get an unresponsive system. Also note, by
                default, kmscon tries to use it's controlling terminal as VT and
                if that fails, it tries to allocate a new unused VT.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--switchvt</option></term>
        <listitem>
          <para>If kmscon is started on a VT that is currently not active, this
                option makes kmscon activate this VT during startup. The same
                way, during shutdown kmscon will reactivate the VT that was
                previously active. (default: on)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--seats {list,of,seats}</option></term>
        <listitem>
          <para>List of seats kmscon will run on. Use 'all' to make kmscon run
                on all seats. Use 'all,' to make kmscon run on a seat called
                'all' (empty entries are ignored). Use 'current' to make kmscon
                run on the current seat. (default: "current")</para>

          <para>If kmscon runs on multiple seats, all seats are independent of
                each other. You can either run a different kmscon process on
                ecah seat or make a single kmscon process run on multiple seats.
                In the latter case, global state can be shared to reduce memory
                consumption (like glyph-caches).</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Session Options:</para>

    <variablelist>
      <varlistentry>
        <term><option>--session-max {num}</option></term>
        <listitem>
          <para>Change the maximum number of sessions that are allowed on each
                seat. Use '0' for no limit. (default: 50)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--session-control</option></term>
        <listitem>
          <para>Allow keyboard-shortcuts to control the session manager. This
                allows the use to create new sessions, kill sessions and switch
                sessions via keyboard input. (default: off)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--terminal-session</option></term>
        <listitem>
          <para>Start a terminal session after setup is done.
                (default: on)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--cdev-session</option></term>
        <listitem>
          <para>Start cdev-VT-emulation session after setup is done. This is
                limited to
                <option>--listen</option> mode. (default: off)</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Terminal Options:</para>

    <variablelist>
      <varlistentry>
        <term><option>-l</option></term>
        <term><option>--login</option></term>
        <listitem>
          <para>Specify the application that is started on new terminal
                sessions. This takes no argument but instead everything left
                after all options have been parsed is used as argument to this
                option. Note that nothing after two dashes <option>--</option>
                is parsed as regular option by kmscon.
                (default: /bin/login -p)</para>

          <para>This example starts '/bin/bash -i' on each new terminal session:
                ./kmscon --login --debug --no-switchvt -- /bin/bash -i</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-t {term}</option></term>
        <term><option>--term {term}</option></term>
        <listitem>
          <para>This changes the <varname>$TERM</varname> environment variable
                that is set on new terminal sessions.
                (default: xterm-256color)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--reset-env</option></term>
        <listitem>
          <para>Reset environment before spawning the child process.
                (default: on)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--palette {name}</option></term>
        <listitem>
          <para>Change the default color-palette. This shouldn't be used
                anymore. Dynamic color palettes should be implemented
                instead.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--sb-size {size}</option></term>
        <listitem>
          <para>Maximum scrollback-buffer line count. (default: 1000)</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Input Options:</para>

    <variablelist>
      <varlistentry>
        <term><option>--xkb-model {model}</option></term>
        <listitem>
          <para>Keyboard model. This should normally not be changed.
                (default: {xkb default})</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--xkb-layout {layout}</option></term>
        <listitem>
          <para>Keyboard layout. (default: {xkb default})</para>
          <para>German keyboard example: --xkb-layout=de</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--xkb-variant {variant}</option></term>
        <listitem>
          <para>Keyboard variant. (default: {xkb default})</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--xkb-options {options}</option></term>
        <listitem>
          <para>Keyboard options. (default: {xkb default})</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--xkb-repeat-delay {delay}</option></term>
        <listitem>
          <para>Delay after key was pressed until key-repeat starts (in
                milliseconds). (default: 250)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--xkb-repeat-rate {rate}</option></term>
        <listitem>
          <para>Time between two key-repeats (in milliseconds).
                (default: 50)</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Grabs / Keyboard-Shortcuts:</para>
    <para>All keyboard shortcuts (here: grabs) in kmscon can be modified with
          these options. The argument to such an option is a list of
          comma-separated
          keyboard-shortcuts that should trigger the specified action. To
          disable a shortcut, pass an empty argument (empty list). A keyboard
          shortcut exists of a list of modifiers followed by a single key. All
          modifiers must be down when the key is pressed for the shortcut to be
          detected. A modifier is sorrounded by '&lt;' and '&gt;' (like
          '&lt;shift&gt;'). A key is the name of a keysym (like 'a' or
          'Return'). Keysyms are case-sensitive and kmscon will suggest a keysym
          name if you entered a wrong case. However, kmscon can not always guess
          the right case as lower-case-only keysyms are ambiguous.</para>

    <para>If a key generates multiple keysyms in your keyboard layout, you can
          match these keys by concatenating the keysyms with a '+' (like
          'H+E+L+L+O'). This does not mean that all the listed keys must be
          pressed! It's rather a way to match multi-keysym keys.</para>

    <para>Valid modifiers are: Shift, Control/Ctrl, Alt, Logo (Windows/Apple
          key)</para>

    <variablelist>
      <varlistentry>
        <term><option>--grab-scroll-up {grab}</option></term>
        <listitem>
          <para>Scroll up in scrollback buffer by one line.
                (default: &lt;Shift&gt;Up)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-scroll-down {grab}</option></term>
        <listitem>
          <para>Scroll down in scrollback buffer by one line.
                (default: &lt;Shift&gt;Down)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-page-up {grab}</option></term>
        <listitem>
          <para>Scroll up in scrollback buffer by one page.
                (default: &lt;Shift&gt;Prior/PageUp)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-page-down {grab}</option></term>
        <listitem>
          <para>Scroll down in scrollback buffer by one page.
                (default: &lt;Shift&gt;Next/PageDown)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-session-next {grab}</option></term>
        <listitem>
          <para>Switch to next session.
                (default: &lt;Ctrl&gt;&lt;Logo&gt;Right)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-session-prev {grab}</option></term>
        <listitem>
          <para>Switch to previous session.
                (default: &lt;Ctrl&gt;&lt;Logo&gt;Left)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-session-dummy {grab}</option></term>
        <listitem>
          <para>Switch to dummy session (black screen).
                (default: &lt;Ctrl&gt;&lt;Logo&gt;Escape)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-session-close {grab}</option></term>
        <listitem>
          <para>Close current session (press twice to kill it).
                (default: &lt;Ctrl&gt;&lt;Logo&gt;BackSpace)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--grab-terminal-new {grab}</option></term>
        <listitem>
          <para>Create new terminal session next to current session.
                (default: &lt;Ctrl&gt;&lt;Logo&gt;Return)</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Video Options:</para>

    <variablelist>
      <varlistentry>
        <term><option>--drm</option></term>
        <listitem>
          <para>Use DRM devices as display devices, too. fbdev devices are
                always used, but DRM devices are only used if this option is on.
                (default: on)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--hwaccel</option></term>
        <listitem>
          <para>Use 3D hardware acceleration. Note that this should be used in
                conjunction with <option>--drm</option>. On newer hardware, this
                can speed up rendering by multiple orders of magnitude. However,
                on older hardware this might even slow down rendering speed.
                (default: off)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--gpus {all,aux,primary}</option></term>
        <listitem>
          <para>GPU selection algorithm. If 'all' then all found GPUs are used.
                If 'aux' then primary and auxiliary GPUs are used. If 'primary'
                then only primary GPUs are used. Primary GPUs are the default
                GPU on a seat. There is always only one primary GPU on a seat.
                Auxiliary GPUs are hotpluggable GPUs that provide additional
                independent displays. (default: all)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--render-engine {engine}</option></term>
        <listitem>
          <para>Select console render engine. Available engines are 'bblit',
                'bbulk' and 'gltex'. (default: detect by GPU type)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--render-timing</option></term>
        <listitem>
          <para>Display timing information of the render engines. This should
                only be used to debug render engines. (default: off)</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Font Options:</para>

    <variablelist>
      <varlistentry>
        <term><option>--font-engine {engine}</option></term>
        <listitem>
          <para>Select font-engine. Available engines are 'pango', 'freetype2',
                'unifont' and '8x16'. (default: pango)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--font-size {points}</option></term>
        <listitem>
          <para>Font size in points. (default: 15)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--font-name {name}</option></term>
        <listitem>
          <para>Font name. (default: monospace)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--font-dpi {dpi}</option></term>
        <listitem>
          <para>DPI used for font-rendering. Per monitor DPI values overwrite
                this global default. (default: 96)</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Default Mode</title>
    <para>In default mode, kmscon acts as a replacement for
          <citerefentry><refentrytitle>agetty</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
          kmscon opens a virtual terminal and
          provides a system console on it. It replaces the linux-console on this
          VT. You can select the virtual terminal
          via the <option>--vt</option> option. kmscon will seamlessly integrate
          into existing setups so you can use X, Wayland or any other Graphics
          Systems simultaneously. You can even use the linux-console on all the
          other virtual terminals.</para>

    <para>By default, kmscon runs on
          <emphasis>seat0</emphasis> but you can change the seat via the
          <option>--seats</option> option. For seats without virtual terminals,
          kmscon will automatically activate itself and run exclusively on that
          seat. If the virtual terminal or the seat that kmscon
          runs on is gone, kmscon will automatically exit. See the
          <emphasis>Listener-Mode</emphasis> to avoid this.</para>

    <para>kmscon spawns
          <citerefentry><refentrytitle>login</refentrytitle><manvolnum>1</manvolnum></citerefentry>
          on each new terminal. After a session exits, kmscon automatically
          respawns the next session. You can change the program that is spawned
          with the <option>--login</option> option. To stop kmscon, send SIGTERM
          to the kmscon process.</para>

    <para>Keyboard input is done by <emphasis>libxkbcommon</emphasis>. This
          provides the same features as the X11 Keyboard System but without any
          dependencies on X11 libraries. See the
          <emphasis>--xkb-{option}</emphasis> options for ways to change the
          keyboard layout, model, repeat rates and more. For instance
          <option>--xkb-layout=de</option> changes the keyboard layout to
          German.</para>

    <para>kmscon uses KMS/DRM to access graphics devices (like the X-Server
          does). Compared to the linux console this allows kmscon to provide
          much better font-rendering and enhanced monitor control. However, for
          backwards compatibility, kmscon can also use fbdev devices.
          Hotpluggable graphics devices are marked as auxiliary devices, primary
          GPUs on a seat are marked as primary. Other GPUs stay unmarked. By
          default kmscon uses all graphics devices but you can make it use only
          primary or auxiliary devices with the <option>--gpus</option>
          option.</para>
  </refsect1>

  <refsect1>
    <title>Listener Mode</title>
    <para>If started in listen-mode (<option>--listen</option>) kmscon will run
          as system daemon and provide a system console on each seat that shows
          up if that seat does not have virtual terminals. On seats with virtual
          terminals you should run kmscon in default mode.</para>

    <para>Several options are exclusively limited to listen-mode, other than
          these, kmscon behaves the same way as in default-mode.</para>
  </refsect1>

  <refsect1>
    <title>Sessions</title>
    <para>If kmscon is active on a seat, the internal session-manager is woken
          up. At most times, only the terminal-session is active, but kmscon can
          also support any other session type. You can switch between sessions
          with keyboard-shortcuts and you can create/destroy sessions during
          runtime.</para>

    <para>Dummy sessions simply show a black screen and are used if no other
          session is available. Otherwise, dummy sessions are hidden from the
          user so they cannot switch to it.</para>

    <para>Terminal sessions provide a terminal emulator. They are the main
          session type and provide all the terminal-emulation
          functionality.</para>

    <para>CDev sessions provide a way to hook-up external applications as kmscon
          sessions. They provide fake virtual terminals on seats that don't have
          them so you can switch between multiple graphics applications/servers
          without needing VTs. See <emphasis>Virtual Terminals</emphasis>
          below.</para>
  </refsect1>

  <refsect1>
    <title>Virtual Terminals</title>
    <para>Historically, linux provides virtual terminals (VT) only on seat
          <emphasis>seat0</emphasis>. This is because only one VT can be active
          at a time but in multi-seat environments you want multiple active VTs,
          one per seat. It is easy to run kmscon on seat0 on a VT, however, if
          you want to run kmscon on another seat, there are no VTs. This means,
          you can only run one application that uses graphics devices on these
          seats. In most environments this is the X-Server. But if you want to
          run kmscon together with the X-Server (or any other graphics server),
          you need a mechanism to notify these servers when they are active.
          This is done via VT APIs on seat0. But note that if the kernel is
          compiled without CONFIG_VT (which controls whether VTs are available),
          then even seat0 does not have VTs.</para>

    <para>On seats without VTs we need a replacement API. However, a new
          API would require modifying every application that uses the VT API to
          also support the new replacement if you want to run it on those seats.
          Therefore, kmscon provides a backwards-compatible API. It uses the
          linux CUSE API to create VTs for all seats that have no VTs. You need
          to pass <option>--cdev-session</option> to kmscon to enable this.
          kmscon will then create one cdev (<emphasis>c</emphasis>haracter
          <emphasis>dev</emphasis>ice) for each seat and calls it
          <filename>/dev/ttyF{seatname}</filename> ('F' for 'fake'). This
          character device provides the same API as a VT so your X-Server (or
          even kmscon in default-mode) can use it instead of a real VT.</para>

    <para>In contrast to real VTs, each application that opens this fake VT will
          get a different VT assigned. So you can use multiple X-Servers all
          opening <filename>/dev/ttyF{seatname}</filename> and they will each
          show up as different kmscon session. But note that not all TTY ioctls
          are available on fake VTs. kmscon only emulates the API that is
          currently used by most VT users. If you want to run an application
          that needs more functionality, please open a bug-report.</para>

    <para>Switching VTs is done by signaling the active process to go asleep and
          signaling the new VT to wake up. If kmscon emulates VTs, it needs to
          be able to send these signals to the processes running on fake VTs. In
          most situations this means kmscon must have root priviledges.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>kmscon.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>console</refentrytitle><manvolnum>4</manvolnum></citerefentry>
    </para>
  </refsect1>
</refentry>