This service publishes CNAME records pointing to the local host over multicast DNS using the Avahi daemon found in all major Linux distributions. Useful as a poor-man's service discovery or as a helper for named virtual-hosts in development environments.
Since Avahi is compatible with Apple's Bonjour, these names are usable from MacOS X and Windows too.
This works well with Traefik and Docker-Dashy-Helper
Git repository of the Docker distribution is on Github Docker-mDNS-Helper
It works out of the box, just:
- Check that Avahi is installed on your system. If not, install it as root:
apt install avahi-daemonfor a Debian or Ubuntu system - Change the configuration in your
/etc/avahi/avahi-daemon.conffile: uncomment or addenable-dbus=yes - Restart avahi. Type as root:
service avahi-daemon restart - Launch docker-mdns-helper:
$ docker run -d --name=mdns -v /var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket -v /var/run/docker.sock:/var/run/docker.sock stefapi/docker-mdns-helper:latest
That's all !
All the configuration is read from container labels (Like Traefik) and the Dashy configuration file is only written if the labels have changed.
CNAMES are defined by the following parameters:
docker-mdns.enable label conditions the following labels. If set to true the labels defined hereunder will be taken into account. if docker-mdns.enable is not specified, the default behavior is to enable the container definition unless the --disable parameter is specified when launching.
It reads the same container labels as Traefik to define CNAMES e.g. :
-l 'traefik.http.routers.r1.rule=Host(`r1example.local`)'
-l 'traefik.https.routers.r1.rule=Host(`r2example.local`, `alterdomain.local`)'
CNAMES may be personalised by using the docker-mdns.domain label like this:
-l 'docker-mdns.domain=r3example.com'
WARNING: Sub domains ( like sub.example.local ) seems not to work on all platforms. Use domains instead (like sub-example.local)
Docker-mdns-helper has no mandatory parameter.
Optional parameter -d or --disable disables the automatic addition of docker containers to Dashy. You have to put the label docker-mdns.enable=true for each container to be added.
Optional parameter -D or --daemon launches the program as a daemon. Only necessary if using it with systemd on host machine.
Optional parameter -l or --log defines the filename to use to write logs to.
Optional parameter -r or --reset when active, all domains which are no more published with a Treafik label or docker-mdns.domain label are removed from avahi. During the reconfiguration no domain published by docker-mdns-helper will be published causing a temporary domain failure
Optional parameter -t or --ttl defines ttl of CNAMES publication. Default 60 seconds.
Optional parameter -w or --wait defines pause between CNAMES scans on Docker. Default 5 seconds.
Optional parameter -v or --verbose increase the level of verbosity of output.
Optional parameter -f or --force publishes a CNAME without prior existence test. Accelerates the publication of CNAMES but if CNAMES are already published, this may crash Avahi.
Following all theses options you could pass a list of CNAMES to publish
docker pull stefapi/docker-mdns-helper
Currently there are AMD64 based builds.
Get git repository:
git pull https://github.com/stefapi/docker-mdns-helper
Build Docker file:
docker build .
You have to attach 2 volumes:
-v /var/run/docker.sock:/var/run/docker.sock
-v /var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket
First is used to read docker configuration and the second is used to communicate with Avahi on host system
Free Sample of container lauch:
$ docker run -d --name=mdns -v /var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket -v /var/run/docker.sock:/var/run/docker.sock stefapi/docker-mdns-helper:latest -r domain.local anotherdomain.local