Linux Commands Examples

A great documentation place for Linux commands


The PulseAudio Sound System

see also : pacmd


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

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How do I recompile libav on ubuntu 12.04 without breaking anything

Looks like it has compiled properly like so:

sudo ./configure --prefix="/home/j/projects/avconv-source/build" --enable-gpl --enable-libmp3lame --enable-libpulse --enable-libx264 --enable-x11grab


Is it possible to route different applications to different audio outputs with Pulse Audio?

Try Ear Candy. It is not only possible to switch between outputs when they're attached, but also to route several programs to other outputs as you're looking for (and lots of other small improvements).


Set device for program in PulseAudio?

I don't know if there is a setting or configuration file for this anywhere but it can be done with environment variables. I've based my answer on this entry in the PulseAudio FAQ about setting the recording source. I've tried this with output (a sink in PulseAudio) but it should work for both input and ouput.

The first step is to get the internal name of the source and sink that you want to use. To do that you need to use the pactl list command. That command will return a pile of data, but the following will list just the source names:

LANG=C pactl list | grep -A2 'Source #' | grep 'Name: ' | cut -d" " -f2

That list will probably include the names for both regular sources and PulseAudio's monitor sources (which on my system have "monitor" in the name). You'll want to use the regular source name of the device you want to target.

You can do the same thing to get the sink names:

LANG=C pactl list | grep -A2 'Sink #' | grep 'Name: ' | cut -d" " -f2

Once you've got the names you can run something like the following from your terminal:

PULSE_SINK=<sink_name> PULSE_SOURCE=<source_name> <command_to_run_skype>

Of course, if you want to run this from a menu you'll probably need to create a shell script and use that instead of the default command. Something like this should work:

set PULSE_SINK <sink_name>
set PULSE_SOURCE <source_name>


Prevent applications to control master volume on Linux

This Gentoo wiki article might apply here : PulseAudio per-application volume control :

PulseAudio supports per-application volume control, but by default this doesn't do much as you can only control these volumes from the pulseaudio volume control utility. Meaning that in an application like Audacious, when the output device is set to PulseAudio, and the volume control is set to hardware, it will adjust the master volume control, not the per-application volume control.

To fix this behavior, set the following in /etc/pulse/daemon.conf

flat-volumes = no

Now whenever Audacious goes to adjust the volume, it will adjust the audacious only volume and thus you wont have multiple applications fighting over the master volume control.


Limit PulseAudio volume to prevent overdrive

I had to set flat-volumes = no in /etc/pulse/daemon.conf in Fedora to stop apps from screwing with volumes. Don't forget to restart PulseAudio after the change.


Does Linux support audio output via USB?

Yes. (However not all USB audio cards are compatible with all systems.)

I'm not sure what you mean by "out of the box" (which box, the computer or the USB sound card...)

According to as long as "You need to turn on the Sound card support kernel option, which is in the Sound section. You will then be able to turn on the USB Audio support option in the normal USB section."


Changing default audio device in Pulseaudio

PulseAudio Device Chooser (padevchooser)?


Reconfigure line-in as analog-out

I just manage to do this on my laptopt, using the mic input instead of line-in.

I did it by following the steps on this AskUbuntu question

I just had to download HDA Analyzer and run it as root:

wget -O
sudo python

Locate the right PIN node (more details about it on askubuntu) uncheck IN and check OUT.

Click on export to save a python script that will make this same changes when run, then add it somwhere on your startup scripts.

I manage to get sound out of my mic jack, but it wasn't pretty. You'll probably have it better since you're using line-in instead of mic.


Why does Pulseaudio selectively detect my sound hardware?

I took a stab at the problem, and randomyl came up with a solution.

Curious about which processes were running, and wanting to start fresh, I ran

$>ps aux | grep pulse

and then killed the first process that looked related to pulse audio

/usr/bin/pulseaudio --start --log-target=syslog

Upon killing the process, which was running as my local user anyways, my volume indicator icon returned to normal, as did sounds. So technically the problem is fixed, but can anyone elaborate on what may have been causing it, and why killing the pulseaudio process restored sound...?


Pulseaudio is no longer working in Debian Squeeze: 'Failed to open module "module-combine-sink": file not found'

Looks like the device drivers are not loading for the sound card.

Try re-configuring alsa, alsactl init and reboot.

EDIT: From your reply it sounds like the kernel package was updated before the crash, and now the new kernel or alsa-base package is giving you problems. There are a bunch of open bugs specific to Intel HD Audio driver.

My recommendation is to reboot and select the previous kernel. You may need to do run altactl init again, but it should work.

The other option (which is what I would do) is install the official driver from RealTek.


PulseAudio is a networked low-latency sound server for Linux, POSIX and Windows systems.


-h | --help

Show help.


Show version information.


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.


List available loadable modules. Combine with -v for a more elaborate listing.


List available audio resamplers.


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 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).


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.


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 startup when any of the commands specified in the startup script (see below) fails.


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).


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 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.


Terminate the daemon when idle and the specified number of seconds passed.


Unload autoloaded samples from the cache when the haven’t been used for the specified number of seconds.


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.


Increase the configured verbosity level by one (see --log-level above). Specify multiple times to increase log level multiple times.


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.


Show source code location in log messages.


Show timestamps in log messages.


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).


Use the specified resampler by default (See --dump-resample-methods above for possible values).


Create a PID file. If this options is disabled it is possible to run multiple sound servers per user.


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.


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).


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 (see below).


Open a command interpreter on STDIN/STDOUT after startup. This may be used to configure PulseAudio dynamically during runtime. Equivalent to --load=module-cli.


Don’t load default script file (see below) on startup. Useful in conjunction with -C or --file.

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).


~/.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/, /etc/pulse/ 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, /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.

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.


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.

see also

pulse-daemon.conf,, pulse-client.conf, pacmd


The PulseAudio Developers <pulseaudio-discuss (at) lists (dot) freedesktop (dot) org>; PulseAudio is available from

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