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mich0w0h
mich0w0h

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Setting up a CoreDNS Server for Local Custom Domain Management on Ubuntu Using Docker

#coredns #ubuntu #docker #beginners

I recently embarked on a journey to set up a CoreDNS server as an authoritative nameserver on my Ubuntu machine to manage a local custom domain, mich0w0h.house, within my home network. This post is one part of building a local DNS service using docker-compose and I'll write other remaining parts later.

Directory Structure

Before diving in, let's take a quick look at the directory structure:

internal-dns │ └── authoritative │ ├── Corefile └── zone └── mich0w0h.house.db
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Prerequisites

Make sure Docker is installed and running on your Ubuntu server.

Creating the Corefile

The Corefile is where we define our CoreDNS configuration. Here's what mine looks like:

mich0w0h.house { file /etc/coredns/zone/mich0w0h.house.db log }
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  • The first line defines zone for this server (default DNS port is 53).
  • file /path/to/your/mich0w0h.house.db tells CoreDNS to load the zone file for your domain.
  • log enables logging ## Creating the Zone File

Now, let's create the zone file mich0w0h.house.db with our DNS records. Here's a snippet of what mine looks like:

$TTL 2d $ORIGIN mich0w0h.house. @ IN SOA ns1.mich0w0h.house. mail.mich0w0h.house. ( 2024031801 3600 600 86400 3600 ) ; Name server resource record for the domain IN NS ns1.mich0w0h.house. ; Domain hosts includes NS records defined above ns1 IN A 192.168.1.102 www IN A 192.168.1.103
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Creating a Docker network

Create a Docker network to enable the container to be accessed by a static IP address.

sudo docker network create --subnet=192.168.1.0/24 internal-dns
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Running the CoreDNS Container

Now, let's fire up the CoreDNS container (run this command in internal-dns directory):

sudo docker container run --rm -d --name authoritative -v $(pwd)/authoritative:/etc/coredns --network internal-dns --ip 192.168.1.102 coredns/coredns -conf /etc/coredns/Corefile
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command explanations

  • --rm: remove container when it stops
  • -d: Runs the container in detached mode (background).
  • --name authoritative: Assigns a name to the container for easier management.
  • -v $(pwd)/authoritative:/etc/coredns: Mounts the directory containing your Corefile into the /etc/coredns directory inside the container. This allows CoreDNS to access your configuration files.
  • -network internal-dns: Specifies the Docker network created at the preliminary step.
  • --ip 192.168.1.102: Set a static IP address for this container. This should be inside of the subnet of specified Docker network
  • coredns/coredns: Specifies the Docker image to use.
  • -conf /etc/coredns/Corefile: let CoreDNS read /etc/coredns/Corefile

Testing with Dig

Finally, let's test our setup using dig on the host ubuntu server:

dig +nocookie @192.168.1.102 ns1.mich0w0h.house
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Now I can see these outputs and it shows the configurations work correctly.

; <<>> DiG 9.18.18-0ubuntu0.22.04.2-Ubuntu <<>> +nocookie @192.168.1.102 ns1.mich0w0h.house ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58701 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1 ;; WARNING: recursion requested but not available ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 1232 ;; QUESTION SECTION: ;ns1.mich0w0h.house. IN A ;; ANSWER SECTION: ns1.mich0w0h.house. 172800 IN A 192.168.1.102 ;; AUTHORITY SECTION: mich0w0h.house. 172800 IN NS ns1.mich0w0h.house. ;; Query time: 3 msec ;; SERVER: 192.168.1.102#53(192.168.1.102) (UDP) ;; WHEN: Tue Mar 19 10:08:10 JST 2024 ;; MSG SIZE rcvd: 127
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What's next

I'll try to create a recursive resolver container and then build a local internal DNS service using docker-compose.

References

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