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<!-- $Id: pulseaudio.1.xml.in 2024 2007-11-05 23:56:00Z lennart $ -->
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This file is part of PulseAudio.
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PulseAudio is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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PulseAudio is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
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Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with PulseAudio; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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<manpage name="pulseaudio" section="1" desc="The PulseAudio Sound System">
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<cmd>pulseaudio [<arg>options</arg>]</cmd>
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<cmd>pulseaudio <opt>--help</opt></cmd>
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<cmd>pulseaudio <opt>--version</opt></cmd>
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<cmd>pulseaudio <opt>--dump-conf</opt></cmd>
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<cmd>pulseaudio <opt>--dump-modules</opt></cmd>
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<cmd>pulseaudio <opt>--dump-resample-methods</opt></cmd>
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<cmd>pulseaudio <opt>--cleanup-shm</opt></cmd>
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<cmd>pulseaudio <opt>--kill</opt></cmd>
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<cmd>pulseaudio <opt>--check</opt></cmd>
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<p>PulseAudio is a networked low-latency sound server for Linux, POSIX and Windows systems.</p>
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<p><opt>-h | --help</opt></p>
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<optdesc><p>Show help.</p></optdesc>
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<p><opt>--version</opt></p>
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<optdesc><p>Show version information.</p></optdesc>
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<p><opt>--dump-conf</opt></p>
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<optdesc><p>Load the daemon configuration file
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<file>daemon.conf</file> (see below), parse remaining
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configuration options on the command line and dump the resulting
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daemon configuration, in a format that is compatible with
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<file>daemon.conf</file>.</p></optdesc>
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<p><opt>--dump-modules</opt></p>
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<optdesc><p>List available loadable modules. Combine with
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<opt>-v</opt> for a more elaborate listing.</p></optdesc>
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<p><opt>--dump-resampe-methods</opt></p>
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<optdesc><p>List available audio resamplers.</p></optdesc>
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<p><opt>--cleanup-shm</opt></p>
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<optdesc><p>Identify stale PulseAudio POSIX shared memory
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segments in <file>/dev/shm</file> and remove them if
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possible. This is done implicitly whenever a new daemon starts
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up or a client tries to connect to a daemon. It should normally
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not be necessary to issue this command by hand. Only available
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on systems with POSIX shared memory segments implemented via a
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virtual file system mounted to <file>/dev/shm</file>
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(e.g. Linux).</p></optdesc>
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<p><opt>-k | --kill</opt></p>
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<optdesc><p>Kill an already running PulseAudio daemon of the
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calling user (Equivalent to sending a SIGTERM).</p></optdesc>
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<p><opt>--check</opt></p>
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<optdesc><p>Return 0 as return code when the PulseAudio daemon
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is already running for the calling user.</p></optdesc>
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<p><opt>--system</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Run as system-wide instance instead of
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per-user. Please not that this disables certain features of
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PulseAudio and is generally not recommended unless the system
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knows no local users (e.g. is a thin client). This feature needs
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special configuration and a dedicated UNIX user set up. It is
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highly recommended to combine this with
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<opt>--disallow-module-loading</opt> (see below).</p></optdesc>
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<p><opt>-D | --daemon</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Daemonize after startup, i.e. detach from the
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terminal.</p></optdesc>
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<p><opt>--fail</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Fail startup when any of the commands specified in
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the startup script <file>default.pa</file> (see below)
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<p><opt>--high-priority</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Try to acquire a high Unix nice level. This will
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only succeed if the calling user has a non-zero RLIMIT_NICE
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resource limit set (on systems that support this), or we're
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called SUID root (see below), or we are configure to be run as
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system daemon (see <arg>--system</arg> above). It is recommended
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to enable this, since it is only a negligible security risk (see
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below).</p></optdesc>
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<p><opt>--realtime</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Try to acquire a real-time scheduling for
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PulseAudio's I/O threads. This will only succeed if the calling
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user has a non-zero RLIMIT_RTPRIO resource limit set (on systems
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that support this), or we're called SUID root (see below), or we
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are configure to be run as system daemon (see
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<arg>--system</arg> above). It is recommended to enable this
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only for trusted users, since it is a major security risk (see
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below).</p></optdesc>
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<p><opt>--disallow-module-loading</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Disallow module loading after startup. This is a
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security feature since it disallows additional module loading
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during runtime and on user request. It is highly recommended
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when <arg>--system</arg> is used (see above). Note however, that
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this breaks certain features like automatic module loading on hot
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<p><opt>--exit-idle-time</opt><arg>=SECS</arg></p>
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<optdesc><p>Terminate the daemon when idle and the specified
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number of seconds passed.</p></optdesc>
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<p><opt>--module-idle-time</opt><arg>=SECS</arg></p>
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<optdesc><p>Unload autoloaded modules when idle and the
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specified number of seconds passed.</p></optdesc>
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<p><opt>--scache-idle-time</opt><arg>=SECS</arg></p>
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<optdesc><p>Unload autoloaded samples from the cache when the
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haven't been used for the specified number of
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seconds.</p></optdesc>
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<p><opt>--log-level</opt><arg>[=LEVEL]</arg></p>
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<optdesc><p>If an argument is passed, set the log level to the
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specified value, otherwise increase the configured verbosity
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level by one. The log levels are numerical from 0 to 4,
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corresponding to <arg>error</arg>, <arg>warn</arg>,
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<arg>notice</arg>, <arg>info</arg>, <arg>debug</arg>. Default
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log level is <arg>notice</arg>, i.e. all log messages with lower
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log levels are printed: <arg>error</arg>, <arg>warn</arg>,
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<arg>notice</arg>.</p></optdesc>
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<optdesc><p>Increase the configured verbosity level by one (see
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<opt>--log-level</opt> above). Specify multiple times to
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increase log level multiple times.</p></optdesc>
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<p><opt>--log-target</opt><arg>={auto,syslog,stderr}</arg></p>
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<optdesc><p>Specify the log target. If set to <arg>auto</arg>
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(which is the default), then logging is directed to syslog when
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<opt>--daemonize</opt> is passed, otherwise to
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STDERR.</p></optdesc>
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<p><opt>--p | --dl-search-path</opt><arg>=PATH</arg></p>
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<optdesc><p>Set the search path for dynamic shared objects
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(plugins).</p></optdesc>
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<p><opt>--resample-method</opt><arg>=METHOD</arg></p>
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<optdesc><p>Use the specified resampler by default (See
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<opt>--dump-resample-methods</opt> above for possible
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values).</p></optdesc>
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<p><opt>--use-pid-file</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Create a PID file. If this options is disabled it is possible to run multiple sound servers per user.</p></optdesc>
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<p><opt>--no-cpu-limit</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>Do not install CPU load limiter on platforms that
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support it. By default, PulseAudio will terminate itself when it
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notices that it takes up too much CPU time. This is useful as a
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protection against system lockups when real-time scheduling is
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used (see below). Disabling this meachnism is useful when
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debugging PulseAudio with tools like <manref name="valgrind"
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section="1"/> which slow down execution.</p></optdesc>
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<p><opt>--disable-shm</opt><arg>[=BOOL]</arg></p>
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<optdesc><p>PulseAudio clients and the server can exchange audio
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data via POSIX shared memory segments (on systems that support
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this). If disabled PulseAudio will communicate exclusively over
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sockets. Please note that data transfer via shared memory
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segments is always disabled when PulseAudio is running with
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<opt>--system</opt> enabled (see above).</p></optdesc>
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<p><opt>-L | --load</opt><arg>="MODULE ARGUMENTS"</arg></p>
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<optdesc><p>Load the specified plugin module with the specified
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arguments.</p></optdesc>
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<p><opt>-F | --file</opt><arg>=FILENAME</arg></p>
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<optdesc><p>Run the specified script on startup. May be
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specified multiple times to specify multiple scripts to be run
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in order. Combine with <opt>-n</opt> to disable loading of the
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default script <file>default.pa</file> (see below).</p></optdesc>
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<optdesc><p>Open a command interpreter on STDIN/STDOUT after
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startup. This may be used to configure PulseAudio dynamically
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during runtime. Equivalent to
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<opt>--load</opt><arg>=module-cli</arg>.</p></optdesc>
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<optdesc><p>Don't load default script file
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<file>default.pa</file> (see below) on startup. Useful in
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conjunction with <opt>-C</opt> or
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<opt>--file</opt>.</p></optdesc>
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<section name="Files">
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<p><file>~/.pulse/daemon.conf</file>,
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<file>@pulseconfdir@/daemon.conf</file>: configuration settings
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for the PulseAudio daemon. If the version in the user's home
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directory does not exist the global configuration file is
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loaded. See <manref name="pulse-daemon.conf" section="5"/> for
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more information.</p>
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<p><file>~/.pulse/default.pa</file>,
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<file>@pulseconfdir@/default.pa</file>: the default configuration
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script to execute when the PulseAudio daemon is started. If the
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version in the user's home directory does not exist the global
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configuration script is loaded. See <manref name="default.pa"
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section="5"/> for more information.</p>
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<p><file>~/.pulse/client.conf</file>,
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<file>@pulseconfdir@/client.conf</file>: configuration settings
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for PulseAudio client applications. If the version in the user's
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home directory does not exist the global configuration file is
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loaded. See <manref name="pulse-client.conf" section="5"/> for
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more information.</p>
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<section name="Signals">
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<p><arg>SIGINT, SIGTERM</arg>: the PulseAudio daemon will shut
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down (Same as <opt>--kill</opt>).</p>
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<p><arg>SIGHUP</arg>: dump a long status report to STDOUT or
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syslog, depending on the configuration.</p>
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<p><arg>SIGUSR1</arg>: load module-cli, allowing runtime
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reconfiguration via STDIN/STDOUT.</p>
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<p><arg>SIGUSR2</arg>: load module-cli-protocol-unix, allowing
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runtime reconfiguration via a AF_UNIX socket. See <manref
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name="pacmd" section="1"/> for more information.</p>
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<section name="UNIX Groups and users">
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<p>Group <arg>pulse-rt</arg>: if the PulseAudio binary is marked
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SUID root, then membership of the calling user in this group
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decides whether real-time and/or high-priority scheduling is
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enabled. Please note that enabling real-time scheduling is a
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security risk (see below).</p>
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<p>Group <arg>pulse-access</arg>: if PulseAudio is running as a system
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daemon (see <opt>--system</opt> above) access is granted to
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members of this group when they connect via AF_UNIX sockets. If
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PulseAudio is running as a user daemon this group has no
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<p>User <arg>pulse</arg>, group <arg>pulse</arg>: if PulseAudio is running as a system
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daemon (see <opt>--system</opt> above) and is started as root the
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daemon will drop priviliges and become a normal user process using
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this user and group. If PulseAudio is running as a user daemon
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this user and group has no meaning.</p>
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<section name="Real-time and high-priority scheduling">
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<p>To minimize the risk of drop-outs during playback it is
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recommended to run PulseAudio with real-time scheduling if the
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underlying platform supports it. This decouples the scheduling
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latency of the PulseAudio daemon from the system load and is thus
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the best way to make sure that PulseAudio always gets CPU time
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when it needs it to refill the hardware playback
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buffers. Unfortunately this is a security risk on most systems,
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since PulseAudio runs as user process, and giving realtime
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scheduling priviliges to a user process always comes with the risk
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that the user misuses it to lock up the system -- which is
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possible since making a process real-time effectively disables
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<p>To minimize the risk PulseAudio by default does not enable
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real-time scheduling. It is however recommended to enable it
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on trusted systems. To do that start PulseAudio with
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<opt>--realtime</opt> (see above) or enabled the appropriate option in
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<file>daemon.conf</file>. Since acquiring realtime scheduling is a
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priviliged operation on most systems, some special changes to the
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system configuration need to be made to allow them to the calling
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user. Two options are available:</p>
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<p>On newer Linux systems the system resource limit RLIMIT_RTPRIO
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(see <manref name="setrlimit" section="2"/> for more information)
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can be used to allow specific users to acquire real-time
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scheduling. This can be configured in
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<file>/etc/security/limits.conf</file>, a resource limit of 9 is recommended.</p>
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<p>Alternatively, the SUID root bit can be set for the PulseAudio
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binary. Then, the daemon will drop root priviliges immediately on
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startup, however retain the CAP_NICE capability (on systems that
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support it), but only if the calling user is a member of the
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<arg>pulse-rt</arg> group (see above). For all other users all
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capababilities are dropped immediately. The advantage of this
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solution is that the real-time priviliges are only granted to the
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PulseAudio daemon -- not to all the user's processes.</p>
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<p>Alternatively, if the risk of locking up the machine is
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considered too big to enable real-time scheduling, high-priority
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scheduling can be enabled instead (i.e. negative nice level). This
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can be enabled by passing <opt>--high-priority</opt> (see above)
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when starting PulseAudio and may also be enabled with the
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approriate option in <file>daemon.conf</file>. Negative nice
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levels can only be enabled when the appropriate resource limit
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RLIMIT_NICE is set (see <manref name="setrlimit" section="2"/> for
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more information), possibly configured in
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<file>/etc/security/limits.conf</file>. A resource limit of 31
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(corresponding with nice level -11) is recommended.</p>
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<section name="Environment variables">
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<p>The PulseAudio client libraries check for the existance of the
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following environment variables and change their local configuration accordingly:</p>
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<p><arg>$PULSE_SERVER</arg>: the server string specifying the server to connect to when a client asks for a sound server connection and doesn't explicitly ask for a specific server.</p>
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<p><arg>$PULSE_SINK</arg>: the symbolic name of the sink to connect to when a client creates a playback stream and doesn't explicitly ask for a specific sink.</p>
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<p><arg>$PULSE_SOURCE</arg>: the symbolic name of the source to connect to when a client creates a record stream and doesn't explicitly ask for a specific source.</p>
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<p><arg>$PULSE_BINARY</arg>: path of PulseAudio executable to run when server auto-spawning is used.</p>
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<p><arg>$PULSE_CLIENTCONFIG</arg>: path of file that shall be read instead of <file>client.conf</file> (see above) for client configuration.</p>
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<p>These environment settings take precedence -- if set -- over the configuration settings from <file>client.conf</file> (see above).</p>
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<section name="Authors">
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<p>The PulseAudio Developers <@PACKAGE_BUGREPORT@>; PulseAudio is available from <url href="@PACKAGE_URL@"/></p>
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<section name="See also">
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<manref name="pulse-daemon.conf" section="5"/>, <manref name="default.pa" section="5"/>, <manref name="pulse-client.conf" section="5"/>, <manref name="pacmd" section="1"/>
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