docker-dns

Run a dns proxy in docker with wildcard host support

This is intended to be used within (but not limited to) a local docker development environment, typically in combination with some type of reverse proxy that supports virtualhosts like nginx. In this configuration, docker-dns allows you to simplify local container access by automatically setting up easier doamins like hello.docker

Quickstart:

docker run -p 53:53/udp -d --restart always finboxio/docker-dns

Once this container is running, configure your system to route DNS queries through localhost and you're all set.

Configuration:

docker-dns can be configured through the use of a few environment variables:

• -e PORT=${PORT:-53} sets the port the DNS server will listen on

• -e EXTERNAL_DNS=${IP:-8.8.8.8} sets the DNS server to which queries that cannot be resolved locally are proxied

• -e HOSTS_FILE=${FILE:-/etc/docker-dns/hosts} -v $FILE:$FILE sets the host file to read for resolving queries locally. This should look like a typical /etc/hosts file, but additionally supports wildcard entries. The default hosts file included in this image is shown below, but you are free to mount your own:

  127.0.0.1 		*.docker
  192.168.99.100 	*.rancher
  

Note:

The second entry is really only effective if you have a rancher host running in a virtual machine with the IP 192.168.99.100. I do some development against a local rancher cluster spun up via mac-ranch, so this is actually a reasonably useful default for me.

Using with a reverse proxy

jwilder/nginx-proxy makes this really easy:

docker run -d -p 80:80 -v /var/run/docker.sock:/tmp/docker.sock:ro --restart always jwilder/nginx-proxy

Note:

Your system may have a default web server already running on port 80. If that's the case you'll either need to disable it or choose a different port. If you're on mac and aren't using the default apache server you can disable it with

sudo launchctl unload -w /System/Library/LaunchDaemons/org.apache.httpd.plist

Now, you can start up any container with VIRTUAL_HOST set to a docker domain and access it from the browser without having to expose/keep track of all the different ports you're using!

docker run -d -p 80 -e VIRTUAL_HOST=hello.docker -e VIRTUAL_PORT=80 tutum/hello-world && open http://hello.docker

#winning

Acknowlegements

DNS proxy code shamelessly copied from hubdotcom/marlon-tools. Thanks for the great work!