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 --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 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.
- --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.
- --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
- Increase the configured verbosity level by one (see
--log-level above). Specify multiple times to increase log level
multiple times.
- --log-target={auto,syslog,stderr,file: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 file:PATH, logging is
directed to the file indicated by PATH.
- --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
meachnism 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 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¶
~/.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.
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
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 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 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 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 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.
ENVIRONMENT VARIABLES¶
The PulseAudio client libraries check for the existance 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.
$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.
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)