This example Uses 4 Raspberry Pi Model 3 A+ each with 16Gb Micro SD Card


Headless Install of Raspbian Lite

Base Image Install

Install Raspbian Buster Lite onto Micro SD Card

Download Raspbial Buster Lite from here 

check the SHA-256 hash matches ( sha256sum <filename> then unzip

Insert Micro SD Card and run sudo fdisk -l to identify the micro sd card

Unmount the above device sudo umount /dev/<device name>1

Apply the image sudo dd bs=1M if=<filename>.img of=/dev/<device name>

remove and rensert the sd card to mount it

O/S Configuration

Enable SSH Access by creating an empty file called ssh in the /boot folder

Enable WIFI access by editing the file /etc/wpa_supplicant/wpa_supplicant.conf and setting the contents to :-

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev

        ssid="<network ssid>"
        psk="<network password>"

Set host name by editing the file /etc/hosts change raspberrypi to dockerx 

also edit /etc/hostname setting the same hostname

Power Up and Install Docker

Get the ip address of each pi and add this to your hosts file

Install docker on each pi 

curl -fsSL -o && sh

 Allow current user to run docker commands

sudo usermod -aG docker pi

 then reboot

the test docker with

docker run hello-world

Create Docker Swarm