qtaudiodockeralsapulseaudio

run apps using audio in a docker container


This question is inspired by Can you run GUI apps in a docker container?.

The basic idea is to run apps with audio and ui (vlc, firefox, skype, ...)

I was searching for docker containers using pulseaudio but all containers I found where using pulseaudio streaming over tcp. (security sandboxing of the applications)

In my case I would prefere playing audio from an app inside the container directly to my host pulseaudio. (without ssh tunneling and bloated docker images)

Pulseaudio because my qt app is using it ;)


Solution

  • it took me some time until i found out what is needed. (Ubuntu)

    we start with the docker run command docker run -ti --rm myContainer sh -c "echo run something"

    ALSA:
    we need /dev/snd and some hardware access as it looks like. when we put this together we have

    docker run -ti --rm \
        -v /dev/snd:/dev/snd \
        --lxc-conf='lxc.cgroup.devices.allow = c 116:* rwm' \
        myContainer sh -c "echo run something"`
    

    In new docker versions without lxc flags you shoud use this:

    docker run -ti --rm \
        -v /dev/snd:/dev/snd \
         --privileged \
        myContainer sh -c "echo run something"`
    

    PULSEAUDIO:
    update: it may be enought to mount the pulseaudio socket within the container using -v option. this depends on your version and prefered access method. see other answers for the socket method.

    Here we need basically /dev/shm, /etc/machine-id and /run/user/$uid/pulse. But that is not all (maybe because of Ubuntu and how they did it in the past). The envirorment variable XDG_RUNTIME_DIR has to be the same in the host system and in your docker container. You may also need /var/lib/dbus because some apps are accessing the machine id from here (may only containing a symbolic link to the 'real' machine id). And at least you may need the hidden home folder ~/.pulse for some temp data (i am not sure about this).

    docker run -ti --rm \
        -v /dev/shm:/dev/shm \
        -v /etc/machine-id:/etc/machine-id \
        -v /run/user/$uid/pulse:/run/user/$uid/pulse \
        -v /var/lib/dbus:/var/lib/dbus \
        -v ~/.pulse:/home/$dockerUsername/.pulse \
        myContainer sh -c "echo run something"
    

    In new docker versions you might need to add --privileged.
    Of course you can combine both together and use it together with xServer ui forwarding like here: https://stackoverflow.com/a/28971413/2835523

    Just to mention:

    create user script:

    mkdir -p /home/$dockerUsername && \
    echo "$dockerUsername:x:${uid}:${gid}:$dockerUsername,,,:/home/$dockerUsername:/bin/bash" >> /etc/passwd && \
    echo "$dockerUsername:x:${uid}:" >> /etc/group && \
    mkdir /etc/sudoers.d && \
    echo "$dockerUsername ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/$dockerUsername && \
    chmod 0440 /etc/sudoers.d/$dockerUsername && \
    chown ${uid}:${gid} -R /home/$dockerUsername