This article walks you through setting up the supporting infrastructure for an air-gapped Coder deployment.

If the network that will run Coder already has the following, skip this tutorial and proceed with the installation process:

• A certificate authority
• A domain name service
• A local Docker Registry

The code snippets provided in this article are sourced from third-party software packages. While we attempt to keep this article up-to-date, we strongly recommend that you verify the snippets before using them.

Creating the local registry and generating a self-signed certificate

Coder needs an image registry to store your images. It uses Docker's Registry 2.0 implementation, which supports self-signed certificates and assumes that the protocol used will be HTTPS. The following steps will show you how to make sure the registry works.

Before starting the registry container, create a self-signed certificate:

export REGISTRY_DOMAINNAME=registry.local
mkdir /certs
openssl req \
    -newkey rsa:4096 -nodes -sha256 -keyout /certs/registry.key \
    -x509 -days 365 -out /certs/registry.crt

The console will prompt you for Common Name [CN]:; provide the value that matches exactly what you set with your DNS. For the volume mounted at /var/lib/registry, make sure that it has at least 10 GB for Coder images.

Start the registry container that you just created:

docker run -d -p 443:5000 \
    -e REGISTRY_HTTP_TLS_CERTIFICATE=/certs/registry.crt \
    -e REGISTRY_HTTP_TLS_KEY=/certs/registry.key \
    -v /certs:/certs \
    -v /var/lib/docker/registry:/var/lib/registry \
    registry:2

For the volume mounted at /var/lib/registry make sure it can store 10+ GB for just Coder images.

Configuring the Kubernetes Node

Before the Kubernetes node can accept local images, it needs to consider the new registry.crt file as trusted. The specific locations and methods to store and trust the certificate vary depending on the Linux distribution and the container runtime, but here is a partial list to help you get started:

/usr/local/share/ca-certificates/registry.crt
/etc/docker/certs.d/${REGISTRY_DOMAIN_NAME}/ca.crt
/etc/ssl/certs/registry.crt
/etc/pki/tls/registry.crt

If the cluster uses containerd, apply the following to patch in certificates for images in the local registry domain:

update-ca-certificates
cat <<EOT >> /etc/containerd/config.toml
[plugins."io.containerd.grpc.v1.cri".registry.configs."$REGISTRY_DOMAIN_NAME".tls]
  insecure_skip_verify = true
EOT
systemctl restart containerd

Because the steps described in this section must be run on all nodes that will be scheduling Coder images, either:

1. Include these steps in the image
2. Run an init script that includes these instructions whenever you add a new node to your cluster

Adding certificate secrets to the Helm chart

Coder validates images and pulls tags using REST API calls to the registry. Other internal services (OIDC, Git providers, etc.) that use HTTPS APIs require the Coder container to trust the certificate. You can fix this by adding a root CA certificate to the Coder service images via the Coder helm chart.

To pass a self-signed certificate to Coder's images, you'll need to:

1. Create a secret
2. Reference the secret in your Coder Helm chart

To create a secret, run:

kubectl -n coder create secret generic local-registry-cert --from-file=/certs

When using the above command, kubectl creates the secret from a directory containing a single file. The directory name doesn't matter, but the filename becomes the secret key.

If you changed the -keyout argument on the OpenSSL command used to generate the certificates, or if you moved the certificates, make sure that you adjust the path included with --from-file=.

To verify the new secret:

kubectl -n coder get secret local-registry-cert -o yaml

Refer to the new secret from the Helm chart by adding the following snippet into a YAML file named registry-cert-values.yml:

certs:
  secret:
    name: "local-registry-cert"
    key: "registry.crt"

Then, add the flag -f registry-cert-values.yml to the end of the helm install or helm upgrade command to include the new secrets file:

helm install --wait --atomic --debug --namespace coder coder . \
   --set coderd.image=$REGISTRY_DOMAIN_NAME/coderenvs/coder-service:<version> \
   --set envbox.image=$REGISTRY_DOMAIN_NAME/coderenvs/envbox:<version> \
   --set timescale.image=$REGISTRY_DOMAIN_NAME/coderenvs/timescale:<version> \
   -f registry-cert-values.yml

Resolving the registry using the cluster's DNS or hostAliases

Nodes must be able to resolve the $REGISTRY_DOMAIN name of the local registry's static IP address. One way to do this without an external DNS server is to use the node's hosts file. For example, if the registry is on 10.0.0.2, then add this to the Node configuration script:

echo "10.0.0.2 $REGISTRY_DOMAIN_NAME" >> /etc/hosts

This modification may not help the containers within the cluster, since Kubernetes forwards some of its DNS services out of the cluster. If, at a later point, you discover that the hosts file on the node isn't being heeded by pods, you can work around this by extracting the Helm chart from coder-X.Y.Z.tgz and patching the coderd deployment (this goes at the same indentation level as containers:):

hostAliases:
  - hostnames:
      - $REGISTRY_DOMAIN_NAME
    ip: 10.0.0.2