Dockerized CUPS on Raspberry Pi
To allow access to a USB printer, execute the following run statement:
docker run -d -p 631:631 --privileged -v /var/run/dbus:/var/run/dbus -v /dev/bus/usb:/dev/bus/usb --name cups a0js/rpi-cupsAccess at http://RPI.IP.ADDRESS:631. When asked for user and password, type print for both.
Bonjour doesn't seem to play nice when the instance is encapsulated in a container. Include -v /var/run/dbus:/var/run/dbus in your run statement to make your shared printer visible to Apple computers.