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Kubernetes at Home on Raspberry Pi 4, Part 2

Continue from part 1

It’s recommended to change all Pi’s password also run ssh-copy-id [email protected] to enable SSH public key login.

There are lots of steps to prepare before kubeadm is installed, so I made this ansible repository to simplify this repeating process. Please see here. The ansible role will do the following tasks:

  • set host name, update /etc/hosts file
  • enable network bridge
  • disable swap, kubeadm doesn’t like it!
  • set timezone. You may want to change it to yours
  • install docker community edition
  • install kubeadm
  • use iptables-legacy (Reference here)

Once the ansible playbook finishes successfully, kubeadm is ready for some action to set up the kubernetes master node, aka. control plane

# the following command is to be run in the master node
# I prefer to use flannelas the CNI(container network interface) because it's lightweight comparing to others like weave.net. So the CIDR is to be set as follow
$ sudo kubeadm init --pod-network-cidr 10.244.0.0/16

Then as the kubeadm finishes it will give some instructions to continue. First thing is to copy the admin.conf so kubectl command can authenticate with the control plane. Also save the kubeadm join 192.168.1.80:6443 --token xxx --discovery-token-ca-cert-hash sha256:xxx instruction as it will be needed later

$ sudo cp -i /etc/kubernetes/admin.conf ~/.kube/config
$ kubectl get node
...
$ kubectl get pods
...

The coredns pods will be at pending state, this is expected. After the CNI is installed this will be fixed automatically. Next step is to install a CNI, in my case it’s flannel. 

$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/62e44c867a2846fefb68bd5f178daf4da3095ccb/Documentation/kube-flannel.yml

In a few minutes the flannel and coredns pods should be in available state. The run the join command saved earlier on other Pi nodes

kubeadm join 192.168.1.80:6443 --token xxx     --discovery-token-ca-cert-hash sha256:xxx

And back to the master node, you should be able to see the new work node in the output

$ kubectl get nodes

TBC

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Kubernetes at Home on Raspberry Pi 4, Part 1

3 x Raspberry Pi 4

I mostly followed/was inspired by this tutorial but with some tweak/fix to recent(Sep 2019) software versions. Also this is a pure Linux walk-through as I don’t use a Mac.

I planned to build a home Kubernetes(k8s) cluster and migrate home servers including the one this blog is running on to the k8s cluster, for a long time. But the Raspberry Pi 2 has 1GB of memory and is not quite appealing for any practical purpose. (I know, I know, we used to run a computer with mega bytes of memory…) When Raspberry Pi 4 with 4GB of memory is available, I believed I need to wait no more.

The 3 Pi 4s I got are from eBay, surprisingly this time the offer in eBay was better than Amazon! I didn’t think I need the cases for the Pis, because I heard the Pi 4 is more powerful and can get hot comparing to previous ones.

I chose Raspbian for now, as it supports all devices in the Pi 4. Ubuntu Server could be a better choice but it only support up to Pi 3. And as a command line veteran I use this line to flash the MicroSD cards:

# if you copy and paste you may need to verify the file name and the card reader device in your computer, ie. I'm not responsible for anything 🙂
$ unzip -p 2019-07-10-raspbian-buster-lite.zip |sudo dd bs=4M of=/dev/mmcblk0

To enable SSH access at first boot, create an empty file called ssh in /boot partition:

# once again, this path could be different on your system.
$ sudo touch /run/media/raynix/boot/ssh

After this, use the sync command to make sure everything has been written to the card. Then you can pull the MicroSD card out of your card reader slot and put it into the Pi 4.

Something required before powering up the Pi 4:

  • Pi 4 connected to the router/switch with Ethernet cable
  • 5V power supply with USB-C connector
  • DHCP enabled in LAN

After the Pi 4 is powered up, the green LED should flash a bit before you can see raspberrypi.localdomain online( the localdomain part is usually the default for some routers, but can be something else depending on your router setup). Then you should be able to:

# default user is pi, and password is raspberry
$ ssh [email protected]
$ cat <<EOF |sudo tee -a /etc/dhcpcd.conf
interface eth0
static ip_address=192.168.1.200/24
static routers=192.168.1.1
static domain_name_servers=192.168.1.1
EOF

This will set the Pi 4 to a static IP address after reboot. Repeat this step for each Pi 4 but obviously they should have different IPs, eg. master has 192.168.1.200 and node1 has 192.168.1.201, etc.

TBC.

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Use FZF to Speed Up KUBECTL

FZF is general purpose option selector for Linux command line. By default fzf is an super-upgrade for the ctrl-r command history finder, but it is helpful for almost any scenario where you need to pick 1 item from a list.

Here’s a tiny use case where I use fzf to select a kubernetes namespace and set it as the default namespace, just to save the effort to type --namespace flag everytime when I need to do something not in the default namespace.

#!/bin/bash
function kns() {
   cns=$(kubectl get namespaces --output=jsonpath='{range .items[*]}{.metadata.name}{"\n"}'|fzf)
   kubectl config set-context --current --namespace=$cns
}

Let me explain the script above step by step:

  1. kubectl get namespaces will list all namespaces currently accessible
  2. --output=jsonpath='{range .items[*]}{.metadata.name}{"\n"}' will only output the name of namespaces and 1 in each line
  3. |fzf to pipe the result from step 2 to fzf, a list will popup and becomes interactive for the user to choose one.
  4. kubectl config set-context --current --namespace=$cns will set the chosen namespace from step 3 as the default namespace

This is very convenient when there are not too many namespaces and when you need to work in different namespaces randomly. 🙂

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AWS Lambda with Single CloudFormation Template

This is just a quick snippet of CloudFormation template to deploy a Python 3.7 Lambda function embedded in the template. The source code inside ZipFile can contain up to 4KB.

# CloudFormation template
AWSTemplateFormatVersion: 2010-09-09
Resources:
  LambdaCode:
    Type: AWS::Lambda::Function
    DependsOn:
      - LambdaRole
      - LambdaPolicy
    Properties:
      Code:
        ZipFile: |
          import boto3
          def handler(event, context):
            ...
      Role: !GetAtt LambdaRole.Arn
      Runtime: python3.7
      Handler: index.handler

Note: the depending LambdaRole is not included, but can be found easily here .

🙂