PulseAudio is a networked low-latency sound server for Linux, POSIX and Windows systems.
~/.config/pulse/daemon.conf,
@PA_DEFAULT_CONFIG_DIR@/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 for
more information.
~/.config/pulse/default.pa,
@PA_DEFAULT_CONFIG_DIR@/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 for more information.
~/.config/pulse/client.conf,
@PA_DEFAULT_CONFIG_DIR@/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 for
more information.
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 for more information.
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.
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 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 for
more information), possibly configured in
/etc/security/limits.conf. A resource limit of 31
(corresponding with nice level -11) is recommended.
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).
The PulseAudio Developers <@PACKAGE_BUGREPORT@>; PulseAudio is available from