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Docker container of dnsmasq, an open-source DNS server.

Usage 🐳

Via Docker Compose:

services:
  dnsmasq:
    image: dockurr/dnsmasq
    container_name: dnsmasq
    environment:
      DNS1: "1.0.0.1"
      DNS2: "1.1.1.1"
    ports:
      - 53:53/udp
      - 53:53/tcp
    cap_add:
      - NET_ADMIN

Via Docker CLI:

docker run -it --rm -p 53:53/udp -p 53:53/tcp -e "DNS1=1.0.0.1" -e "DNS2=1.1.1.1" --cap-add=NET_ADMIN dockurr/dnsmasq

Configuration ⚙️

You can set the DNS1 and DNS2 environment variables to change which upstream DNS servers to use.

For example, you can set them to the public Cloudflare servers like this:

environment:
  DNS1: "1.0.0.1"
  DNS2: "1.1.1.1"

You can extend the default configuration with a volume that mounts a directory containing *.conf configuration files:

volumes:
  - /example/dnsmasq.d/:/etc/dnsmasq.d/

You can also override dnsmasq.conf completely with a volume that binds your custom configuration file:

volumes:
  - /example/dnsmasq.conf:/etc/dnsmasq.conf

FAQ 💬

  • Port 53 is already in use?

If some process on the host is already binding to port 53, you may see an error similar to the following:

Error response from daemon: driver failed programming external connectivity on
endpoint dnsmasq (...): Error starting userland proxy: listen tcp4 0.0.0.0:53: bind:
address already in use

You can inspect which process is binding to that port:

$ netstat -lnpt | grep -E ':53 +'
tcp    0    0 127.0.0.53:53    0.0.0.0:*    LISTEN    197/systemd-resolve

On hosts running systemd, such as in this example, you can workaround this by specifying the IP addresses on which to bind port 53, for example:

ports:
  - "192.168.1.###:53:53/udp"
  - "192.168.1.###:53:53/tcp"

There are many other host-specific cases where some process and configuration binds port 53. It may be an unused DNS daemon, such as bind that needs to be uninstalled or disabled, or a number of other causes. So finding out which process is binding the port is a good place to start debugging.

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