.. title: Building k3s on a Pi
.. date: 2020-08-09
.. slug: building-k3s-on-a-pi
.. updated: 2020-08-09
.. status: published
.. tags: kubernetes, k3s, arm
.. category: k3s
.. authors: Elia el Lazkani
.. description: I have decided to make a better use of my pi, k3s came next.
.. type: text

I have had a **Pi** laying around used for a simple task for a while now. 
A few days ago, I was browsing the web, learning more about privacy, when I stumbled upon `AdGuard Home <https://adguard.com/en/welcome.html>`_.

I have been using it as my internal DNS on top of the security and privacy layers I add to my machine.
Its benefits can be argued but it is a DNS after all and I wanted to see what else it can do for me.
Anyway, I digress. I searched to see if I could find a container for **AdGuard Home** and I did.

At this point, I started thinking about what I could do to make the `Pi <https://www.raspberrypi.org/>`_ more useful.

That's when `k3s <https://k3s.io/>`_ came into the picture.

.. TEASER_END

Pre-requisites
==============

As this is not a **Pi** tutorial, I am going to be assuming that you have a *Raspberry Pi* with **Raspberry Pi OS** *Buster* installed on it.
The assumption does not mean you cannot install any other OS on the Pi and run this setup.
It only means that I have tested this on *Buster* and that your milage will vary.

Prepare the Pi
==============

Now that you have *Buster* already installed, let's go ahead and `fix <https://rancher.com/docs/k3s/latest/en/advanced/#enabling-legacy-iptables-on-raspbian-buster>`_ a small default configuration issue with it.

**K3s** uses ``iptables`` to route things around correctly. *Buster* uses ``nftables`` by default, let's switch it to ``iptables``.

.. code:: text

    $ sudo iptables -F
    $ sudo update-alternatives --set iptables /usr/sbin/iptables-legacy
    $ sudo update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy
    $ sudo reboot

At this point, your *Pi* should reboot. Your **OS** is configured for the next step.

Pre-install Configuration
=========================

After testing **k3s** a few times, I found out that by *default* it will deploy a few extra services like `Traefik <https://docs.traefik.io/>`_.

Unfortunately, just like anything the *default* configuration is just that. It's plain and not very useful from the start. You will need to tweak it.

This step could be done either *post* or *pre* deploy. Figuring out the *pre-deploy* is a bit more involving but a bit more fun as well.

The first thing you need to know is that the normal behavior of **k3s** is to deploy anything found in ``/var/lib/rancher/k3s/server/manifests/``.
So a good first step is, of course, to proceed with creating that.

.. code:: text

    $ mkdir -p /var/lib/rancher/k3s/server/manifests/

The other thing to know is that **k3s** can deploy *Helm Charts*. 
It will create the *manifests* it will deploy by default, before beginning the setup, in the manifest path I mentioned.
If you would like to see what it deployed and how, visit that path after **k3s** runs. 
I did, and I took their configuration of **Traefik** which I was unhappy with its *defaults*.

My next step was securing the *defaults* as much as possible and I found out that **Traefik** can do `basic authentication <https://docs.traefik.io/v2.0/middlewares/basicauth/>`_.
As a starting point, that's great. Let's create the credentials.

.. code:: text

    $ htpasswd -c ./auth myUser

That was easy so far. Let's turn up the notch and create the manifest for **k3s**.

Create ``traefik.yaml`` in ``/var/lib/rancher/k3s/server/manifests/`` with the following content.

.. code:: yaml

    ---
    apiVersion: helm.cattle.io/v1
    kind: HelmChart
    metadata:
      name: traefik
      namespace: kube-system
    spec:
      chart: https://%{KUBERNETES_API}%/static/charts/traefik-1.81.0.tgz
      valuesContent: |-
        rbac:
          enabled: true
        ssl:
          enabled: true
        dashboard:
          enabled: true
          domain: traefik-ui.example.com
          auth:
            basic:
              myUser: $ars3$4A5tdstr$trSDDa4467Tsa54sTs.
        metrics:
          prometheus:
            enabled: false
        kubernetes:
          ingressEndpoint:
            useDefaultPublishedService: true
        image: "rancher/library-traefik"
        tolerations:
          - key: "CriticalAddonsOnly"
            operator: "Exists"
          - key: "node-role.kubernetes.io/master"
            operator: "Exists"
            effect: "NoSchedule"

It's a **Pi**, I don't need prometheus so I disabled it.
I also enabled the dashboard and added the credentials we created in the previous step.

Now, the *Helm Chart* will deploy an ingress and expose the dashboard for you on the value of ``domain``.

.. note::

    I figured out the values to set in ``valuesContent`` by reading the *Helm Chart*

K3s
===

If everything is in place, you are ready to proceed. 
You can install **k3s**, now, but before I get to that step, I will say a few things about **k3s**.

**K3s** has a smaller feature set than **k8s**, hence the smaller footprint. 
Read the documentation to see if you need any of the missing features.
The second thing to mention is that **k3s** is a one binary deploy that uses **containerd**. 
That's why we will use the script installation method as it adds the necessary **systemd** configuration for us.
It is a nice gesture.

Let's do that, shall we ?

.. code:: text

    $ curl -sfL https://get.k3s.io | sh -s - --no-deploy traefik

.. note::

    We need to make sure that **k3s** does not deploy its own **traefik** but ours.
    Make sure to add ``--no-deploy traefik`` to our deployment command.

Point ``traefik.example.com`` to your **Pi** ``IP`` in ``/etc/hosts`` on your machine.

.. code:: text

    traefik.example.com  192.168.0.5

When the installation command is done, you should be able to visit `http://traefik.example.com/ <http://traefik.example.com/>`_

You can get the *kubeconfig* from the *Raspberry Pi*, you can find it in ``/etc/rancher/k3s/k3s.yaml``.
You will need to change the ``server`` **IP**.

Conclusion
==========

If you've made it so far, you should have a **k3s** cluster running on a single *Raspberry Pi*.
The next steps you might want to look into is disable the *metrics* server and use the resources for other things.