Ubuntu Manpage: pulseaudio - The PulseAudio Sound System

Provided by: pulseaudio_11.1-1ubuntu7.11_amd64

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 they 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/