pulseaudio(1)pulseaudio(1)NAMEpulseaudio - The PulseAudio Sound System
SYNOPSISpulseaudio [options]
pulseaudio--help
pulseaudio--version
pulseaudio--dump-conf
pulseaudio--dump-modules
pulseaudio--dump-resample-methods
pulseaudio--cleanup-shm
pulseaudio--start
pulseaudio--kill
pulseaudio--check
DESCRIPTION
PulseAudio is a networked low-latency sound server for Linux, POSIX and
Windows systems.
OPTIONS-h | --help
Show help.
--version
Show version information.
--dump-conf
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.
--dump-modules
List available loadable modules. Combine with -v for a more
elaborate listing.
--dump-resample-methods
List available audio resamplers.
--cleanup-shm
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 com‐
mand 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
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 ini‐
tialized when this call returns. Implies --daemon.
-k | --kill
Kill an already running PulseAudio daemon of the calling user
(Equivalent to sending a SIGTERM).
--check
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.
--system[=BOOL]
Run as system-wide instance instead of per-user. Please note
that this disables certain features of PulseAudio and is gener‐
ally not recommended unless the system knows no local users
(e.g. is a thin client). This feature needs special configura‐
tion and a dedicated UNIX user set up. It is highly recommended
to combine this with --disallow-module-loading (see below).
-D | --daemonize[=BOOL]
Daemonize after startup, i.e. detach from the terminal.
--fail[=BOOL]
Fail startup when any of the commands specified in the startup
script default.pa (see below) fails.
--high-priority[=BOOL]
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).
--realtime[=BOOL]
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 config‐
ure to be run as system daemon (see --system above). It is rec‐
ommended to enable this only for trusted users, since it is a
major security risk (see below).
--disallow-module-loading[=BOOL]
Disallow module loading after startup. This is a security fea‐
ture 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 fea‐
tures like automatic module loading on hot plug.
--disallow-exit[=BOOL]
Disallow user requested exit
--exit-idle-time=SECS
Terminate the daemon when idle and the specified number of sec‐
onds passed.
--scache-idle-time=SECS
Unload autoloaded samples from the cache when the haven't been
used for the specified number of seconds.
--log-level[=LEVEL]
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,
warn, notice.
-v | --verbose
Increase the configured verbosity level by one (see --log-level
above). Specify multiple times to increase log level multiple
times.
--log-target={auto,syslog,journal,stderr,file:PATH,newfile:PATH}
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. If set to journal logging is directed to
the systemd journal. If set to file:PATH, logging is directed to
the file indicated by PATH. newfile:PATH is otherwise the same
as file:PATH, but existing files are never overwritten. If the
specified file already exists, a suffix is added to the file
name to avoid overwriting.
--log-meta[=BOOL]
Show source code location in log messages.
--log-time[=BOOL]
Show timestamps in log messages.
--log-backtrace=FRAMES
When FRAMES is greater than 0, log for each message a stack
trace up to the number of specified stack frames.
-p | --dl-search-path=PATH
Set the search path for dynamic shared objects (plugins).
--resample-method=METHOD
Use the specified resampler by default (See --dump-resample-
methods above for possible values).
--use-pid-file[=BOOL]
Create a PID file. If this options is disabled it is possible to
run multiple sound servers per user.
--no-cpu-limit[=BOOL]
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 mechanism is useful when debugging
PulseAudio with tools like valgrind(1) which slow down execu‐
tion.
--disable-shm[=BOOL]
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
(see above).
-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
below).
-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.
FILES
~/.config/pulse/daemon.conf, /etc/pulse/daemon.conf: configuration set‐
tings 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.
~/.config/pulse/default.pa, /etc/pulse/default.pa: the default configu‐
ration script to execute when the PulseAudio daemon is started. If the
version in the user's home directory does not exist the global configu‐
ration script is loaded. See default.pa(5) for more information.
~/.config/pulse/client.conf, /etc/pulse/client.conf: configuration set‐
tings 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.
SIGNALS
SIGINT, SIGTERM: the PulseAudio daemon will shut down (Same as --kill).
SIGHUP: dump a long status report to STDOUT or syslog, depending on the
configuration.
SIGUSR1: load module-cli, allowing runtime reconfiguration via
STDIN/STDOUT.
SIGUSR2: load module-cli-protocol-unix, allowing runtime reconfigura‐
tion via a AF_UNIX socket. See pacmd(1) for more information.
UNIX GROUPS AND USERS
Group pulse-rt: if the PulseAudio binary is marked SUID root, then mem‐
bership 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 privi‐
leges 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 mean‐
ing.
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 sys‐
tems, since PulseAudio runs as user process, and giving realtime sched‐
uling privileges 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 privileged 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/secu‐
rity/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 privileges immediately on startup, how‐
ever 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 capabilities are dropped immediately. The
advantage of this solution is that the real-time privileges are only
granted to the PulseAudio daemon -- not to all the user's processes.
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 appropriate 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 (corre‐
sponding with nice level -11) is recommended.
ENVIRONMENT VARIABLES
The PulseAudio client libraries check for the existence of the follow‐
ing environment variables and change their local configuration accord‐
ingly:
$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. The server string is a list of server
addresses separated by whitespace which are tried in turn. A server
address consists of an optional address type specifier (unix:, tcp:,
tcp4:, tcp6:), followed by a path or host address. A host address may
include an optional port number.
$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
sink.
$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 spe‐
cific source.
$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.
$PULSE_COOKIE: path of file that contains the PulseAudio authentication
cookie. Defaults to ~/.config/pulse/cookie.
These environment settings take precedence -- if set -- over the con‐
figuration settings from client.conf (see above).
AUTHORS
The PulseAudio Developers <pulseaudio-discuss (at) lists (dot)
freedesktop (dot) org>; PulseAudio is available from http://pulseau‐
dio.org/
SEE ALSOpulse-daemon.conf(5), default.pa(5), pulse-client.conf(5), pacmd(1)Manuals User pulseaudio(1)
