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Docker DNS image on steroids to access DNS-over-TLS by Cloudflare or other providers (Google, Quad9, etc.)
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hooks Added hooks/build and changed image size in readme Oct 29, 2018

Cloudflare DNS over TLS Docker container

DNS caching server connected to Cloudflare DNS over TLS (IPv4) with DNSSEC, DNS rebinding protection, built-in Docker healthcheck and malicious IPs + hostnames blocking

NEW (13 January 2019): Supports all other DNS-over-TLS providers: Google, Quad9, Quadrant and CleanBrowsing

Cloudflare DNS over TLS Docker

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Image size Image version

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Image size RAM usage CPU usage
17MB 13.2MB to 70MB Low

It is based on:

It also uses DNS rebinding protection and DNSSEC Validation:

DNSSEC Validation

You can also block additional domains of your choice, amongst other things, see the Extra section

Diagrams are shown for router and client-by-client configurations in the Connect clients to it section.

Testing it

docker run -it --rm -p 53:53/udp -e VERBOSITY=3 -e VERBOSITY_DETAILS=3 qmcgaw/cloudflare-dns-server

More environment variables are described in the environment variables section.

You can check the verbose output with:

docker logs -f cloudflare-dns-tls

See the Connect clients to it section to finish testing, and you can refer to the Verify DNS connection section if you want.

Run it as a daemon

docker run -d -p 53:53/udp qmcgaw/cloudflare-dns-server

or use docker-compose.yml with:

docker-compose up -d

More environment variables are described in the environment variables section.

Environment variables

Environment variable Default Description
VERBOSITY 1 From 0 (no log) to 5 (full debug log)
VERBOSITY_DETAILS 0 From 0 to 4 and defaults to 0 (higher means more details)
BLOCK_MALICIOUS on on or off. It blocks malicious IP addresses and malicious hostnames from being resolved. Note that it consumes about 50MB of additional RAM.
LISTENINGPORT 53 UDP port on which the Unbound DNS server should listen to (internally)
PROVIDER cloudflare DNS-over-TLS provider. It can be: google, quad9, quadrant, cleanbrowsing

Connect clients to it

Option 1: Router (recommended)

Block the UDP 53 outgoing port on your router firewall so that all DNS traffic must go through this container.

All machines connected to your router will use the encrypted DNS by default

Configure your router to use the LAN IP address of your Docker host as its primary DNS address.

  • Access your router page, usually at and login with your credentials
  • Change the DNS settings, which are usually located in Connection settings / Advanced / DNS server
  • If a secondary fallback DNS address is required, use a dull ip address such as the router's IP to force traffic to only go through this container

Option 2: Client, one by one

You have to configure each machine connected to your router to use the Docker host as their DNS server.

Docker containers

Connect other Docker containers by specifying the DNS to be the host IP address

docker run -it --rm --dns= alpine

For docker-compose.yml:

version: '3'
    image: alpine:3.8
    network_mode: bridge

If the containers are in the same virtual network, you can simply set the dns to the LAN IP address of the DNS container (i.e.


  1. Open the control panel and follow the instructions shown on the screenshots below.

Enter the IP Address of your Docker host as the Preferred DNS server ( in my case) You can set the Cloudflare DNS server address as an alternate DNS server although you might want to leave this blank so that no domain name request is in plaintext.

When closing, Windows should try to identify any potential problems. If everything is fine, you should see the following message:

Mac OS

Follow the instructions at


You probably know how to do that. Otherwise you can usually modify the first line of /etc/resolv.conf by changing the IP address of your DNS server.


See this


See this


Block domains of your choice

  1. Create a file on your host include.conf

  2. Write the following to the file to block for example:

    local-zone: "" static
  3. Change the ownership and permissions of include.conf:

    chown 1000:1000 include.conf
    chmod 400 include.conf
  4. Launch the Docker container with:

    docker run -it --rm -p 53:53/udp -v $(pwd)/include.conf:/etc/unbound/include.conf  qmcgaw/cloudflare-dns-server

Build the image yourself

docker build -t qmcgaw/cloudflare-dns-server

Firewall considerations

This container requires the following connections:

  • UDP 53 Inbound (only if used externally)
  • TCP 853 Outbound to and

Verify DNS connection

  1. Verify that you use Cloudflare DNS servers: with the Standard or Extended test
  2. Verify that DNS SEC is enabled:

Note that does not work as the container is not a client to Cloudflare servers but a forwarder intermediary. Hence does not detect a direct connection to them.


  • Build Unbound binary at image build stage
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