pulseaudio(1)
NAME
pulseaudio - The PulseAudio Sound System
SYNOPSIS
pulseaudio [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
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
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 --daemonize.
-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
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
below).
-D | --daemonize[=BOOL]
Daemonize after startup, i.e. detach from the terminal. Note
that when running as a systemd service you should use
--daemonize=no for systemd notification to work.
--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
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[=BOOL]
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.
--disallow-exit[=BOOL]
Disallow user requested exit
--exit-idle-time=SECS
Terminate the daemon when idle and the specified number of
seconds 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
execution.
--disable-shm[=BOOL]
PulseAudio clients and the server can exchange audio data via
POSIX or memfd 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).
--enable-memfd[=BOOL]
PulseAudio clients and the server can exchange audio data via
memfds - the anonymous Linux Kernel shared memory mechanism (on
kernels that support this). If disabled PulseAudio will
communicate via POSIX shared memory.
-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 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. ~/.config/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. ~/.config/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.
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 reconfiguration 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 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 privileges 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 meaning.
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 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/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 privileges 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 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 (corresponding with nice level -11) is recommended.
ENVIRONMENT VARIABLES
The PulseAudio client libraries check for the existence of the
following environment variables and change their local configuration
accordingly:
$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. A server address may be prefixed by a
string enclosed in {}. In this case the following server address is
ignored unless the prefix string equals the local hostname or the
machine id (/etc/machine-id).
$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
specific 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
configuration settings from client.conf (see above).
AUTHORS
The PulseAudio Developers <pulseaudio-discuss (at) lists (dot) freedesktop (dot) org>; PulseAudio is available from http://pulseaudio.org/
SEE ALSO
pulse-daemon.conf(5), default.pa(5), pulse-client.conf(5), pacmd(1)
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