Kubernetes

1 Master and 1 Node

Assumptions:

• Master and Node are on the same network (in this example 10.1.1.0/24)
• IP of the Master: 10.1.1.2
• IP of the first Node: 10.1.1.3

Caveats:

• this is probably not best-practice?

Master

Add to your configuration.nix:

{ config, pkgs, ... }:
let
  kubeMasterIP = "10.1.1.2";
  kubeMasterHostname = "api.kube";
  kubeMasterAPIServerPort = 443;
in
{
  # resolve master hostname
  networking.extraHosts = "${kubeMasterIP} ${kubeMasterHostname}";

  # packages for administration tasks
  environment.systemPackages = with pkgs; [
    kompose
    kubectl
    kubernetes
  ];

  services.kubernetes = {
    roles = ["master" "node"];
    apiserver = {
      securePort = ${kubeMasterAPIServerPort};
      advertiseAddress = ${kubeMasterIP};
    };
    masterAddress = ${kubeMasterHostname};
    easyCerts = true;
  };

  # needed if you use swap
  services.kubernetes.kubelet.extraOpts = "--fail-swap-on=false";
}

Apply your config (e.g. nixos-rebuild switch).

Link your kubeconfig to your home directory:

ln -s /etc/kubernetes/cluster-admin.kubeconfig ~/.kube/config

Now, executing kubectl cluster-info should yield something like this:

Kubernetes master is running at https://10.1.1.2
CoreDNS is running at https://10.1.1.2/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
KubeDashboard is running at https://10.1.1.2/api/v1/namespaces/kube-system/services/https:kubernetes-dashboard:/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

You should also see that the master is also a node using kubectl get nodes:

NAME       STATUS   ROLES    AGE   VERSION
direwolf   Ready    <none>   41m   v1.16.6-beta.0

Node

Add to your configuration.nix:

{ config, pkgs, ... }:
let
  kubeMasterIP = "10.1.1.2";
  kubeMasterHostname = "api.kube";
  kubeMasterAPIServerPort = 443;
in
{

}

Multiple Masters (HA)

This article or section needs expansion.

Reason: How to set this up? (Discuss in Talk:Kubernetes#)
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Debugging

systemctl status kubelet
systemctl status kube-apiserver
kubectl get nodes

Sources

• Kubernetes docs
• NixOS e2e kubernetes tests: Node Joining etc.
• IRC (2018-09): issues related to DNS
• IRC (2019-09): discussion about easyCerts and general setup