I chose k3s as it incredibly lightweight but still CNCF certified and production grade software that is optimised for resource constraints of raspberry pis.

Pre-requisites

Cluster machines

For this guide I am using three Raspberry Pi 4 4GB machines.

The cluster will have two leader node and two worker nodes.

For resiliency puposes in future I will consider updateing the cluster to run with all nodes as leader nodes.

Boot media

This guide requires each Raspberry Pi to have a removable SD card or other removable boot media. I am use three 32GB SD Cards though any USB or SD card at least 8GB in size should work fine.

TODO Migration to network booting

In future it would be preferable for the raspberry pi's to be able to network boot and setup automatically without an SD card.

This is a nice to have that I will pursue at a later date once I have a deployed cluster that allows me to migrate off the current server setup I have deployed.

Step 1 - Prepare boot media for master

Download the latest release

Our first step is to create the bootable SD Card with a minimal install of Raspbian, which is a free operating system based on Debian and is optimised for Raspberry Pi hardware.

Rather than doing an installation and configuration of an operating system image from scratch I found this project on Github which automates the install and configuration process nicely.

echo Downloading latest release zip from github
curl -s https://api.github.com/repos/foodeas/raspberrypi-ua-netinst/releases/latest \
| grep "browser_download_url.*zip" \
| cut -d : -f 2,3 \
| tr -d \" \
| wget -i -

echo Checking file is now present
ls -l | grep *.zip

echo Extracting the zip file
unzip -q -d installer *.zip
ls -l | grep installer

Downloading latest release zip from github
Checking file is now present
-rw-rw-rw- 1 james james 60299545 Aug 12 08:35 raspberrypi-ua-netinst-v2.4.0.zip
Extracting the zip file
drwxrwxrwx 1 james james     4096 Jan 20 11:12 installer
-rwxrwxrwx 1 james james     2863 Jan 10 17:04 installer-config.txt

Apply custom install configuration

Our next step after downloading the latest release is to apply our own installation configuration using a simple txt file.

There is great documentation online howing what configuration options are available here.

For our purposes we just over-write the file downloaded and extracted in the previous step with one we have prepared earlier :)

echo Display wordcount of original file for comparison
wc installer/raspberrypi-ua-netinst/config/installer-config.txt

echo Overwriting /installer/raspberrypi-ua-netinst/config/installer-config.txt
cp installer-config.txt installer/raspberrypi-ua-netinst/config/

echo Display wordcount of file after copy to validate update
wc installer/raspberrypi-ua-netinst/config/installer-config.txt

Display wordcount of original file for comparison
  3  23 157 installer/raspberrypi-ua-netinst/config/installer-config.txt
Overwriting /installer/raspberrypi-ua-netinst/config/installer-config.txt
Display wordcount of file after copy to validate update
  67   85 2863 installer/raspberrypi-ua-netinst/config/installer-config.txt

Apply custom post install script

The final step is to supply a post install script which completes additional security hardening and production readiness automatically.

To supply a script we can provide an additional post-install.txt file as documented here.

I have a hardening script prepared in this repository that we can copy in.

echo Copying in post-install.txt
cp post-install.txt installer/raspberrypi-ua-netinst/config/

echo Display wordcount of file after copy to validate
wc installer/raspberrypi-ua-netinst/config/post-install.txt

Copying in post-install.txt
Display wordcount of file after copy to validate
  98  282 3429 installer/raspberrypi-ua-netinst/config/post-install.txt

Step 2 - Copy the install media to sd card

Our next step is to copy the contents of the installer/ folder to a FAT32 formatted SD Card.

Unfortunately this is currently a windows step as my dev environment is a Windows 10 laptop with Debian via Windows Subsystem for Linux which does not support lsblk or other disk management commands.

Obtain sd card partition information

Our first step is to insert the SD Card and ensure it is formatted correctly as FAT32. To do that we need to know the number of the disk we want to format, we can find that via powershell.

echo Retrieving disk list via powershell
powershell.exe -nologo 
get-disk | select Number, FriendlyName, Size

echo Retrieving partition list via powershell
get-disk | get-partition | select PartitionNumber, DriveLetter, Size, Type
exit

Retrieving disk list via powershell

Number FriendlyName                       Size
------ ------------                       ----
     1 Realtek PCIE Card Reader    31104958464
     0 SAMSUNG MZVLB256HAHQ-000H1 256060514304

Retrieving partition list via powershell

PartitionNumber DriveLetter         Size Type        
--------------- -----------         ---- ----        
              1           D    268435456 FAT32 XINT13
              2           E  30832328704 Unknown     
              1                272629760 System      
              2                 16777216 Reserved    
              3           C 254735810560 Basic       
              4               1027604480 Recovery

Create and format sd card partition

Once we know the number of the disk we want to format we can proceed. In the example above I have a 32GB SD Card which shows as number 1.

Checking the disk we can see some partitions that exist already from previous use of the card. To delete these partitions you can use the Remove-Partition -DiskNumber X -PartitionNumber Y command where X and Y relate to the output of your disk and partition number.

Due to the risk of data loss this step is not automated. Once existing partitions have been cleared we can use the following block to:

Create a new partition using masixmum available space
Assign a free drive letter in windows
Mount the disk in WSL so we can copy to it
Copy the install media over to the partition

echo Use powershell to create new partition and format 
powershell.exe -nologo
new-partition -disknumber 1 -usemaximumsize -driveletter d
format-volume -driveletter d -filesystem FAT32 -newfilesystemlabel sd
exit

echo Mount the new partition in wsl
sudo mkdir /mnt/d
sudo mount -t drvfs d: /mnt/e/

echo Copy the contents of installer to sd
cp -r installer/* /mnt/d/

echo Eject the sd card ready for use
powershell.exe -nologo
(new-object -comobject shell.application).namepsace(17).parsename("E:").invokeverb("eject")
exit

Step 3 - Boot the pi and remotely connect

Provided the configuration on the sd card is valid and the pi has been able to successfully obtain an ip address via dhcp on boot then following a 10-20minute net install process the pi will be online and accessible via ssh using the private key corresponding to the public key we supplied in our installer-config.txt file.

Setup ssh and connect

First step, we ensure our ssh agent is running and has our key added.

# Ensure our ssh-agent is running.
eval `ssh-agent`

# Make sure our private key is added.
ssh-add ~/.ssh/james

Next we can port knock and connect.

# Setup machine variables
export port=2122
export machineip=192.168.1.122  
export knocksequence=[SEQUENCE HERE]

# Knock and enter
knock $machineip $knocksequence && ssh -p $port $machineip

Setup glusterfs storage cluster

Now that our machines are online and we have connected we can setup our storage cluster.

For a distributed storage cluster we are using glusterfs. As part of our earlier setup gluster was automatically installed. We just need to configure it.

Our first step is to ensure our storage drives attached to our raspberry pi's are formatted. In our case our drives are all showing as /dev/sda with no existing partitions, ensure you review your situation with lsblk first and ajdust the commands below as neccessary!

# Format the /dev/sda1 partition as xfs
sudo mkfs.xfs -i size=512 /dev/sda1

# Make the mount point directory
sudo mkdir -p /data/brick1

# Update fstab to ensure the mount will resume on boot
echo '/dev/sda1 /data/brick1 xfs defaults 1 2' | sudo tee -a /etc/fstab

# Mount the new filesystem now
sudo mount -a && sudo mount

The gluster processes on the nodes need to be able to communicate with each other. To simplify this setup, configure the firewall on each node to accept all traffic from the other node.

In our four node cluster this means ensuring we have rules present for all nodes. Adjust as neccessary for the requirements of your cluster!

# Add the firewall rules
sudo iptables -I INPUT -p all -s 192.168.1.122 -j ACCEPT
sudo iptables -I INPUT -p all -s 192.168.1.124 -j ACCEPT
sudo iptables -I INPUT -p all -s 192.168.1.126 -j ACCEPT
sudo iptables -I INPUT -p all -s 192.168.1.128 -j ACCEPT

# Ensure these are saved permanently
sudo netfilter-persistent save

Next we need to ensure the glusterfs daemon is enabled and started.

# Ensure the gluster service starts on boot
sudo systemctl enable glusterd

# Start the gluster service now
sudo systemctl start glusterd

# Check the service status to confirm running
sudo systemctl status glusterd

Now we're ready to test connectivity between all the gluster peers.

# Complete the peer probes
sudo gluster peer probe 192.168.1.122
sudo gluster peer probe 192.168.1.124
sudo gluster peer probe 192.168.1.126
sudo gluster peer probe 192.168.1.128

# Validate the peer status
sudo gluster peer status

Provided connectivity was established successfully you are now ready to setup a gluster volume.

Note: The gluster volume create command only needs to be run from any one node.

# Create the gluster volume folder (all nodes)
sudo mkdir -p /data/brick1/jammaraid 

# Create the gluster volume itself (one node)
sudo gluster volume create jammaraid 192.168.1.122:/data/brick1/jammaraid 192.168.1.124:/data/brick1/jammaraid 192.168.1.126:/data/brick1/jammaraid 192.168.1.128:/data/brick1/jammaraid force

# Ensure the volume is started
sudo gluster volume start jammaraid  

# Confirm the volume has been created
sudo gluster volume info

Now that the gluster volume has been created and started we can mount it within each node so it is accessible for use :)

# Create the gluster volume mount point
sudo mkdir -p /media/raid

# Mount the volume
sudo mount -t glusterfs localhost:jammaraid /media/raid