Raspberry Pi with MicroK8s.

Raspberry PI Overview

Hardware

Raspberry Pi 4 Model B with 2GB RAM
MicroSD Card 32 GB
Raspberry Pi 15W USB-C Power supply (works better with this)
Armor Case "BLOCK"
DisplayPort cable (for initial setup)
Logitech Wireless Keyboard (for initial setup)

Install Ubuntu

Instructions which are the basis for these notes: https://ubuntu.com/blog/single-node-kubernetes-on-raspberry-pi-microk8s-ubuntu

Create Boot Image

The image from Ubuntu (I used 19.10 64-bit): https://ubuntu.com/download/raspberry-pi

For writing the image to an MicroSD card: https://www.balena.io/etcher/

Boot and configure the image

Use the DisplayPort cable and Keyboard for this part. Afterwards, connect using SSH over the Wireless connection.

$ cat /etc/netplan/50-cloud-init.yaml
    network:
        ethernets:
            eth0:
                dhcp4: true
                optional: true
        version: 2
        wifis:
             wlan0:
                 access-points:
                         "X":
                                 password: "Y"
                 dhcp4: true
                 optional: true
$ sudo netplan apply
$ ip a
$ cat /boot/firmware/config.txt
$ cat /boot/firmware/nobtcmd.txt
    cgroup_enable=... cgroup_enable=memory cgroup_memory=1 ...       <=== add these
$ sudo apt-get install snapd
$ sudo reboot

Configure "ubuntu" user

System Info

$ uname -a
    Linux ubuntu 5.3.0-1022-raspi2 #24-Ubuntu SMP Fri Mar 27 21:32:13 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux
$ lsb_release  -a
    No LSB modules are available.
    Distributor ID: Ubuntu
    Description:    Ubuntu 19.10
    Release:        19.10
    Codename:       eoan
$ free -h
                  total        used        free      shared  buff/cache   available
    Mem:          1.8Gi       948Mi       320Mi       4.0Mi       579Mi       865Mi
    Swap:            0B          0B          0B
$ ifconfig
    ...
    wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
    inet 192.168.1.24  netmask 255.255.255.0  broadcast 192.168.1.255
    inet6 fe80::dea6:32ff:fe27:c5a1  prefixlen 64  scopeid 0x20<link>
    ether dc:a6:32:27:c5:a1  txqueuelen 1000  (Ethernet)
    RX packets 268391  bytes 379681903 (379.6 MB)
    RX errors 0  dropped 1  overruns 0  frame 0
    TX packets 60681  bytes 6533026 (6.5 MB)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
    ...

Install MicroK8s

$ sudo snap install microk8s --classic
$ sudo usermod -a -G microk8s ubuntu


$ microk8s.inspect
$ sudo journalctl -u snap.microk8s.daemon-kubelet
$ sudo systemctl restart snap.microk8s.daemon-kubelet

$ microk8s.enable dashboard dns ingress storage
$ token=$(microk8s kubectl -n kube-system get secret | grep default-token | cut -d " " -f1)
$ microk8s kubectl -n kube-system describe secret $token
$ microk8s.status
    microk8s is running
    addons:
    dashboard: enabled
    dns: enabled
    ingress: enabled
    storage: enabled
    helm: disabled
    helm3: disabled
    kubeflow: disabled
    metallb: disabled
    metrics-server: disabled
    rbac: disabled
    registry: disabled

# Not sure what these were for (could be suggestions from microk8s.inspect)
$ sudo journalctl -u snap.microk8s.daemon-kubelet
$ sudo systemctl restart snap.microk8s.daemon-kubelet

Access the Dashboard

$ token=$(microk8s kubectl -n kube-system get secret | grep default-token | cut -d " " -f1)
$ microk8s kubectl -n kube-system describe secret
$token$ k port-forward -n kube-system service/kubernetes-dashboard 10443:443 --address 0.0.0.0

Navigate to : https://192.168.1.24:10443 and enter the token (from above).

Setup Ingress for TCP and UDP

Both TCP and UDP traffic can be proxied by the NGINX Ingress Controller which is included with MicroK8s. To enable this functionality the Ingress Controller must be patched, and a pair of ConfigMaps created (one for each of TCP and UDP).

$ git clone https://github.com/trulede/raspberry.microk8s.git
$ cd raspberry.microk8s/services/ingress
$ k -n ingress patch daemonset nginx-ingress-microk8s-controller --patch "$(cat ingress-patch.yaml)"
    daemonset.apps/nginx-ingress-microk8s-controller patched
$ k -n ingress apply -f ingress-configmap.yaml
    configmap/nginx-ingress-tcp-services-conf created
    configmap/nginx-ingress-udp-services-conf created
$ k -n ingress get daemonset
    NAME                                DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
    nginx-ingress-microk8s-controller   1         1         1       1            1           <none>          6d11h
$ k -n ingress get configmap
    NAME                                DATA   AGE
    ingress-controller-leader-nginx     0      6d10h
    nginx-ingress-tcp-services-conf     0      14s
    nginx-ingress-udp-services-conf     0      14s
    nginx-load-balancer-microk8s-conf   0      6d10h
$ k -n ingress get daemonset/nginx-ingress-microk8s-controller -o yaml
    apiVersion: apps/v1
    kind: DaemonSet
    metadata:
      name: nginx-ingress-microk8s-controller
      namespace: ingress
     spec:
      ...
      template:
        ...
        spec:
          containers:
          - args:
            - /nginx-ingress-controller
            - --configmap=$(POD_NAMESPACE)/nginx-load-balancer-microk8s-conf
            - --tcp-services-configmap=$(POD_NAMESPACE)/nginx-ingress-tcp-services-conf
            - --udp-services-configmap=$(POD_NAMESPACE)/nginx-ingress-udp-services-conf
            - --publish-status-address=127.0.0.1

More information can be found at these links:

Use the K8s (single node) Cluster

Before setting up any of the following services on your Raspberry Pi run the following commands:

$ git clone https://github.com/trulede/raspberry.microk8s.git
$ cd raspberry.microk8s/services
$ k apply -f namespace.yaml

Redis

First install a Redis Container into the "pi" namespace.

$ cd raspberry.microk8s/services/redis
$ k apply -f redis.yaml
$ k -n pi get services,pods
    NAME            TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
    service/redis   ClusterIP   10.152.183.122   <none>        6379/TCP   45s

    NAME                         READY   STATUS    RESTARTS   AGE
    pod/redis-6fbc78dc54-9xpvv   1/1     Running   0          44s

Then patch the Ingress Controller and TCP ConfigMap to enable the proxy of incoming TCP connections send them to the Redis Service.

$ k -n ingress patch daemonset nginx-ingress-microk8s-controller --patch "$(cat redis-patch-ingress-daemonset.yaml)"
    daemonset.apps/nginx-ingress-microk8s-controller patched
$ k -n ingress patch configmap nginx-ingress-tcp-services-conf --patch "$(cat redis-patch-ingress-tcp-configmap.yaml)"
    configmap/nginx-ingress-tcp-services-conf patched

Finally install the Redis CLI and check things are working.

$ sudo apt install redis-tools
$ k -n pi get service
    NAME    TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
    redis   ClusterIP   10.152.183.238   <none>        6379/TCP   10h
$ redis-cli
    127.0.0.1:6379> set foo bar
    OK
    127.0.0.1:6379> get foo
    "bar"
    127.0.0.1:6379> keys *
    1) "foo"
    127.0.0.1:6379> exit

Alternative method using port-forward (rather than then Ingress Controller).

$ k -n pi port-forward deployment/redis 6379:6379 &
    [1] 18995
    Forwarding from 127.0.0.1:6379 -> 6379
    Forwarding from [::1]:6379 -> 6379
$ redis-cli
    Handling connection for 6379
    127.0.0.1:6379> set foo bar
    OK
    127.0.0.1:6379> get foo
    "bar"
    127.0.0.1:6379> keys *
    1) "foo"
    127.0.0.1:6379> exit
$ fg 1
    microk8s.kubectl -n pi port-forward deployment/redis 6379:6379
    <CTRL C>

Minecraft

Original from: https://github.com/itzg/docker-minecraft-bedrock-server

Warning: The Minecraft Server deployment to Raspberry Pi does not work. If you decide to run it and find your Pi becomes unresponsive, the easiest way to recover the system is to restart the Pi and quickly delete the "pi" namespace: k delete namespaces pi

The following commands install a Minecraft Bedrock Server with a 1 GB volume and configuration for the Ingress Controller.

$ cd raspberry.microk8s/services/minecraft
$ k apply -f minecraft.yaml
    persistentvolumeclaim/minecraft created
    deployment.apps/minecraft created
    service/minecraft created
$ k -n pi get services,pods
$ k get pvc
$ k -n ingress patch daemonset nginx-ingress-microk8s-controller --patch "$(cat minecraft-patch-ingress-daemonset.yaml)"
    daemonset.apps/nginx-ingress-microk8s-controller patched
$ k -n ingress patch configmap nginx-ingress-udp-services-conf --patch "$(cat minecraft-patch-ingress-udp-configmap.yaml)"
    configmap/nginx-ingress-udp-services-conf patched