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.
- --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 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
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.
$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)