This is a guide on how to build a six node Raspberry Pi cluster running K3s: Lightweight Kubernetes
The following shopping list will have the bare essentials you will need to get a "High Available" cluster working, and the specific products I used for my first hardware cluster setup. However, you might choose a different case or cooling solution for example. Currently HA is not working on K3s, but it will eventually, and then we'll be ready! However having a high available control plane might not be necessary.
6x Raspberry Pi 3 model B+
6x Micro SD card (Class 10, 8GB+)
6x USB A to USB Micro B cable
1x Anker Powerport 6
1x Switch: 8 ports
7x RJ45 Ethernet cables
6x Heatsinks
1x Case
1x Router (Optional: If you don't want to setup DHCP yourself)
6x Raspberry Pi 3 model B+
6x Micro SD cards (Class 10, 16 GB)
1x Anker Powerport 10
1x Switch: 8 ports (D-Link GO-SW-8E, should have gotten the GO-SW-8G)
7x RJ45 Ethernet cables
6x Heatsink, 3-piece set
1x Tower case: for six Pi's
4x Cooling fans (12V, 4cm by 4cm)
1x DC-DC Step-up Boost Converter XL6009 4A: To supply the 12V from a 5V USB source
1x USB to type M cable: (Only useful if you have a switch with a 5V input like the D-Link GO-SW-8E or GO-SW-8G)
6x RGB Leds: https://shop.pimoroni.com/products/blinkt
1x Power button: Reset button, to power on and off the Pi's
1x Power button: On/Off, for the cooling fans (faster than setting up the circuit to switch a transistor from one of the Pi's, but on the to-do list!)
If you'd like to know how I created the hardware go to: Setup hardware
Go to https://www.raspberrypi.org/downloads/ and use whatever OS image you like. I used "Raspbian Stretch with desktop". However, I recommend using the Rasbian Strech Lite image, if you can find your way around the OS just fine from the cli and if you have a smaller sized SD card. The setup was quite easy, so I will be using the Lite image in the future as well.
I won't be reinventing the wheel, so just follow: https://www.raspberrypi.org/documentation/installation/installing-images/README.md to install the OS image.
After flashing the image and placing the SD card in your Pi, connect a monitor to the HDMI port and connect the micro-USB cable to power up the Pi.
If you installed the desktop version you can follow: Desktop setup
If you're doing it from the CLI you can follow: https://www.raspberrypi.org/documentation/configuration/raspi-config.md and change the user password and enable SSH.
Go to: Setup DHCP and Networking
Go to: Setup K3s server
Go to: Setup K3s agent
You can setup the sleep/wake-up button by running the rpi-cluster-k3s/scripts/button.sh script. This will create a listen-for-shutdown.sh script, places it in /etc/init.d, makes it executable and registers it to run on boot.