What

A Docker image to run an Apple AirPlay Protocol receiver.

This is currently based on shairport-sync and the ALAC library.

This image also ships experimental support for Airplay 2 based on goplay2.

Image features

• multi-architecture:
  • linux/amd64
  • linux/arm64
  • linux/arm/v7
  • linux/arm/v6
• hardened:
  • image runs read-only
  • image runs with no cap
  • process runs as a non-root user, disabled login, no shell
  • shairport-sync is compiled with PIE, bind now, stack protection, fortify source and read-only relocations (additionally stack clash protection on amd64)
• lightweight
  • based on our slim Debian Bullseye
  • simple entrypoint script
  • multi-stage build with no installed dependencies for the runtime image
• observable
  • healthcheck
  • logs to stdout
• other achitectures (386, ppc64le, s390x) probably build as well, though they are disabled by default

Run

docker run -d --rm \
    --name "airplay" \
    --env MDNS_NAME="My Fancy Airplay Receiver" \
    --group-add audio \
    --device /dev/snd \
    --net host \
    --cap-drop ALL \
    --read-only \
    ghcr.io/dubo-dubon-duponey/airplay

Notes

Networking

You need to run this in host or mac(or ip)vlan networking (because of mDNS).

Additional arguments

The following environment variables allow for high-level control over shairport:

• OUTPUT (alsa|pipe|stdout) controls the output
• LOG_LEVEL if set to "debug" will pass along -vvv and --statistics
• MDNS_NAME controls the announced name
• PORT controls the port to bind to

Any additional arguments passed when running the image will get fed to the shairport-sync binary directly.

You can get a full list of supported arguments with:

docker run --rm ghcr.io/dubo-dubon-duponey/airplay --help

This is specifically convenient for example to address a different Alsa card or mixer (eg: -- -d hw:1).

Custom configuration file

For more advanced control over shairport-sync configuration, mount /config/shairport-sync/main.conf.

Linkage

The shairport binary links dynamically against:

• libasound2
• libsoxr0
• libconfig9
• libpopt0
• libssl1.1
• libgomp.so.1
• libstdc++.so.6
• libcrypto.so.1.1

These are copied over from the build stage into the final image in /boot/lib.

Also, libalac is built in statically.

About soxr

Soxr support is compiled in, though in our experience we had bad results on RPI using it, hence we advise against using it on low-end hardware and do rely on "basic" instead by default.

If you want to use soxr, just pass it as an extra argument ("--stuffing=soxr") or change the config file corresponding setting.

About mDNS

We do not support Avahi, and instead rely on tinymdns. Setting-up avahi in a container is doable (and we did before in this image), but it's a PITA and requires you to setup dbus and an avahi daemon process on top of shairport, so, no thank you.

Experimental Airplay 2 support

shairport-sync does not support it right now, and it appears unlikely to be implemented for the time being. See mikebrady/shairport-sync#535 for details.

If you set AIRPLAY_VERSION=2, goplay2 is used instead of shairport-sync.

Caveats:

• this is largely experimental at this point, and probably buggy
• goplay2 ignores the following: OUTPUT and PORT
• goplay2 does require NET_BIND_SERVICE to work properly
• goplay2 requires pulseaudio to be installed in the runtime image
• goplay2 is not compiled the way it should, and has a number of issues:
  • it will create its configuration and write data under the current working directory
  • config and data are mixed in the same location

To start goplay2:

docker run -d --rm \
--name "airplay2" \
--env MDNS_NAME="My Fancy Airplay 2 Receiver" \
--group-add audio \
--device /dev/snd \
--net host \
--cap-drop ALL \
--cap-add NET_BIND_SERVICE \
--read-only \
ghcr.io/dubo-dubon-duponey/airplay

Moar?

See DEVELOP.md