Provided by: pulseaudio_0.9.14-0ubuntu20_i386
pulseaudio - The PulseAudio Sound System
PulseAudio is a networked low-latency sound server for Linux, POSIX and
-h | --help
Show version information.
Load the daemon configuration file daemon.conf (see below),
parse remaining configuration options on the command line and
dump the resulting daemon configuration, in a format that is
compatible with daemon.conf.
List available loadable modules. Combine with -v for a more
List available audio resamplers.
Identify stale PulseAudio POSIX shared memory segments in
/dev/shm and remove them if possible. This is done implicitly
whenever a new daemon starts up or a client tries to connect to
a daemon. It should normally not be necessary to issue this
command by hand. Only available on systems with POSIX shared
memory segments implemented via a virtual file system mounted to
/dev/shm (e.g. Linux).
Start PulseAudio if it is not running yet. This is different
from starting PulseAudio without --start which would fail if PA
is already running. PulseAudio is guaranteed to be fully
initialized when this call returns. Implies --daemon.
-k | --kill
Kill an already running PulseAudio daemon of the calling user
(Equivalent to sending a SIGTERM).
Return 0 as return code when the PulseAudio daemon is already
running for the calling user, or non-zero otherwise. Produces no
output on the console except for errors to stderr.
Run as system-wide instance instead of per-user. Please note
that this disables certain features of PulseAudio and is
generally not recommended unless the system knows no local users
(e.g. is a thin client). This feature needs special
configuration and a dedicated UNIX user set up. It is highly
recommended to combine this with --disallow-module-loading (see
-D | --daemonize[=BOOL]
Daemonize after startup, i.e. detach from the terminal.
Fail startup when any of the commands specified in the startup
script default.pa (see below) fails.
Try to acquire a high Unix nice level. This will only succeed if
the calling user has a non-zero RLIMIT_NICE resource limit set
(on systems that support this), or we’re called SUID root (see
below), or we are configure to be run as system daemon (see
--system above). It is recommended to enable this, since it is
only a negligible security risk (see below).
Try to acquire a real-time scheduling for PulseAudio’s I/O
threads. This will only succeed if the calling user has a non-
zero RLIMIT_RTPRIO resource limit set (on systems that support
this), or we’re called SUID root (see below), or we are
configure to be run as system daemon (see --system above). It is
recommended to enable this only for trusted users, since it is a
major security risk (see below).
Disallow module loading after startup. This is a security
feature since it disallows additional module loading during
runtime and on user request. It is highly recommended when
--system is used (see above). Note however, that this breaks
certain features like automatic module loading on hot plug.
Terminate the daemon when idle and the specified number of
Unload autoloaded modules when idle and the specified number of
Unload autoloaded samples from the cache when the haven’t been
used for the specified number of seconds.
If an argument is passed, set the log level to the specified
value, otherwise increase the configured verbosity level by one.
The log levels are numerical from 0 to 4, corresponding to
error, warn, notice, info, debug. Default log level is notice,
i.e. all log messages with lower log levels are printed: error,
-v Increase the configured verbosity level by one (see --log-level
above). Specify multiple times to increase log level multiple
Specify the log target. If set to auto (which is the default),
then logging is directed to syslog when --daemonize is passed,
otherwise to STDERR.
--p | --dl-search-path=PATH
Set the search path for dynamic shared objects (plugins).
Use the specified resampler by default (See --dump-resample-
methods above for possible values).
Create a PID file. If this options is disabled it is possible to
run multiple sound servers per user.
Do not install CPU load limiter on platforms that support it. By
default, PulseAudio will terminate itself when it notices that
it takes up too much CPU time. This is useful as a protection
against system lockups when real-time scheduling is used (see
below). Disabling this meachnism is useful when debugging
PulseAudio with tools like valgrind(1) which slow down
PulseAudio clients and the server can exchange audio data via
POSIX shared memory segments (on systems that support this). If
disabled PulseAudio will communicate exclusively over sockets.
Please note that data transfer via shared memory segments is
always disabled when PulseAudio is running with --system enabled
-L | --load="MODULE ARGUMENTS"
Load the specified plugin module with the specified arguments.
-F | --file=FILENAME
Run the specified script on startup. May be specified multiple
times to specify multiple scripts to be run in order. Combine
with -n to disable loading of the default script default.pa (see
-C Open a command interpreter on STDIN/STDOUT after startup. This
may be used to configure PulseAudio dynamically during runtime.
Equivalent to --load=module-cli.
-n Don’t load default script file default.pa (see below) on
startup. Useful in conjunction with -C or --file.
~/.pulse/daemon.conf, /etc/pulse/daemon.conf: configuration settings
for the PulseAudio daemon. If the version in the user’s home directory
does not exist the global configuration file is loaded. See pulse-
daemon.conf(5) for more information.
~/.pulse/default.pa, /etc/pulse/default.pa: the default configuration
script to execute when the PulseAudio daemon is started. If the version
in the user’s home directory does not exist the global configuration
script is loaded. See default.pa(5) for more information.
~/.pulse/client.conf, /etc/pulse/client.conf: configuration settings
for PulseAudio client applications. If the version in the user’s home
directory does not exist the global configuration file is loaded. See
pulse-client.conf(5) for more information.
SIGINT, SIGTERM: the PulseAudio daemon will shut down (Same as --kill).
SIGHUP: dump a long status report to STDOUT or syslog, depending on the
SIGUSR1: load module-cli, allowing runtime reconfiguration via
SIGUSR2: load module-cli-protocol-unix, allowing runtime
reconfiguration via a AF_UNIX socket. See pacmd(1) for more
UNIX GROUPS AND USERS
Group pulse-rt: if the PulseAudio binary is marked SUID root, then
membership of the calling user in this group decides whether real-time
and/or high-priority scheduling is enabled. Please note that enabling
real-time scheduling is a security risk (see below).
Group pulse-access: if PulseAudio is running as a system daemon (see
--system above) access is granted to members of this group when they
connect via AF_UNIX sockets. If PulseAudio is running as a user daemon
this group has no meaning.
User pulse, group pulse: if PulseAudio is running as a system daemon
(see --system above) and is started as root the daemon will drop
priviliges and become a normal user process using this user and group.
If PulseAudio is running as a user daemon this user and group has no
REAL-TIME AND HIGH-PRIORITY SCHEDULING
To minimize the risk of drop-outs during playback it is recommended to
run PulseAudio with real-time scheduling if the underlying platform
supports it. This decouples the scheduling latency of the PulseAudio
daemon from the system load and is thus the best way to make sure that
PulseAudio always gets CPU time when it needs it to refill the hardware
playback buffers. Unfortunately this is a security risk on most
systems, since PulseAudio runs as user process, and giving realtime
scheduling priviliges to a user process always comes with the risk that
the user misuses it to lock up the system -- which is possible since
making a process real-time effectively disables preemption.
To minimize the risk PulseAudio by default does not enable real-time
scheduling. It is however recommended to enable it on trusted systems.
To do that start PulseAudio with --realtime (see above) or enabled the
appropriate option in daemon.conf. Since acquiring realtime scheduling
is a priviliged operation on most systems, some special changes to the
system configuration need to be made to allow them to the calling user.
Two options are available:
On newer Linux systems the system resource limit RLIMIT_RTPRIO (see
setrlimit(2) for more information) can be used to allow specific users
to acquire real-time scheduling. This can be configured in
/etc/security/limits.conf, a resource limit of 9 is recommended.
Alternatively, the SUID root bit can be set for the PulseAudio binary.
Then, the daemon will drop root priviliges immediately on startup,
however retain the CAP_NICE capability (on systems that support it),
but only if the calling user is a member of the pulse-rt group (see
above). For all other users all capababilities are dropped immediately.
The advantage of this solution is that the real-time priviliges are
only granted to the PulseAudio daemon -- not to all the user’s
Alternatively, if the risk of locking up the machine is considered too
big to enable real-time scheduling, high-priority scheduling can be
enabled instead (i.e. negative nice level). This can be enabled by
passing --high-priority (see above) when starting PulseAudio and may
also be enabled with the approriate option in daemon.conf. Negative
nice levels can only be enabled when the appropriate resource limit
RLIMIT_NICE is set (see setrlimit(2) for more information), possibly
configured in /etc/security/limits.conf. A resource limit of 31
(corresponding with nice level -11) is recommended.
The PulseAudio client libraries check for the existance of the
following environment variables and change their local configuration
$PULSE_SERVER: 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.
$PULSE_SINK: the symbolic name of the sink to connect to when a client
creates a playback stream and doesn’t explicitly ask for a specific
$PULSE_SOURCE: the symbolic name of the source to connect to when a
client creates a record stream and doesn’t explicitly ask for a
$PULSE_BINARY: path of PulseAudio executable to run when server auto-
spawning is used.
$PULSE_CLIENTCONFIG: path of file that shall be read instead of
client.conf (see above) for client configuration.
These environment settings take precedence -- if set -- over the
configuration settings from client.conf (see above).
The PulseAudio Developers <mzchyfrnhqvb (at) 0pointer (dot) net>;
PulseAudio is available from http://pulseaudio.org/
pulse-daemon.conf(5), default.pa(5), pulse-client.conf(5), pacmd(1)