Section: User Commands (1)
~/.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 (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 (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 (5) 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.
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.
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.
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.
The PulseAudio Developers <pulseaudio-discuss (at) lists (dot) freedesktop (dot) org>; PulseAudio is available from http://pulseaudio.org/
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