Containers on k3s

How does one run containers on k3s? Here are a few things I did to play around with my cluster.

Syntax

The following syntax describes how to run kubectl commands from the terminal:

kubectl [command] [TYPE] [NAME] [flags]

• command specifies the operation to be performed
• TYPE specifies the resource type (e.g. pod, node, deployment, service)
• NAME specifies the name of the resource
• flags specifies optional flags

Documentation: kubectl run

BusyBox

BusyBox is a suite of tools for Linux that provides a shell interface. The image is useful for testing as a running container because the image is lightweight. I used the following command to ephemerally run the container on k3s:

k3s kubectl run -it --rm --restart=Never busybox-test --image=busybox sh

Breakdown

• k3s : CLI for k3s
• kubectl : CLI for Kubernetes (wrapped by k3s)
• run : kubectl command
• -it : make the container interactive
• -rm : delete the pod after it exits. Only valid when attaching to the container, e.g. with ‘–attach’ or with ‘-i/–stdin’
• --restart=Never : do not restart the container upon exit
• busybox-test : the resource name (used by k8s)
• --image=busybox : specifies busybox as the image to build the container
• sh : requests sh access to busybox shell in container

Helm

Did you know there was a package manager for Kubernetes clusters? Helm is a tool useful for installing Charts which is a Helm package containing all resource definitions necessary to run some application, tool, or service on a k8s cluster. In addition to Charts, Helm also embodies two other concepts: a Repository is the place where charts can be collected and shared and a Release is an instance of a chart running on a k8s cluster. From the Helm intro: “Helm installs charts into Kubernetes, creating a new release for each installation. And to find new charts, you can search Helm chart repositories.”

Using Helm, I can leverage my k3s cluster by making use of existing Helm charts.

OpenVPN

I want to run a simple VPN server on my network. It won’t handle crazy traffic and I’m mostly trying this just for the sake of learning.

First, I installed Helm to node1 so that I could use the openvpn-as helm chart. I used the following command to add charts from stenic to the Helm package repositories:

helm repo add stenic https://stenic.github.io/helm-charts

The next command deploys the container:

 helm install openvpn-ml --set "service.type=LoadBalancer" stenic/openvpn-as

I initally encountered this error after running the helm install command:

Error: INSTALLATION FAILED: Kubernetes cluster unreachable: Get "http://localhost:8080/version": dial tcp [::1]:8080: connect: connection refused

The error stems from Helm trying to make use of the same configuration file used by Kubernetes. Since I am running k3s, the following command sets the KUBECONFIG environment variable to point to the k3s configuration:

export KUBECONFIG=/etc/rancher/k3s/k3s.yaml

Now, Helm should be able to install the chart and make use of the k3s cluster.

Result

I was not able to get OpenVPN properly set up as the pod running OpenVPN Access Server has a status of CrashLoopBackoff but it does appear that the chart was able to deploy 12 running pods.