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Node Configuration

Overview​

This guide will go over the basic OS/hardware config on a Raspberry Pi, along with some additional apps/tunings to help things play nicely further in the series.

Step 1 - Install Raspberry Pi OS​

The following YouTube video, provided by the Raspberry Pi Foundation is a great overview on how to use their excellent imaging software to write a Raspberry Pi OS image to a MicroSD Card.
I would recommend the usage of the 64bit lite release.

Step 2 - Connect via SSH to the Raspberry Pi (RPi)​

Once installed, connect your RPi to your home network, wait for it to boot, and then SSH in to begin configuring.

A good guide for this step is again available from the RPi website - here

Step 3 - Base Configuration​

Adjust RAM Allocation for GPU to 16Mb​

The display output on the RPi will not be used, so lets claim some extra RAM back for the system to use. 

sudo raspi-config

Navigate -

  1. Performance Options-> GPU Memory
  2. Change to '16'
  3. Back
tip

You can do this manually by editing the /boot/config.txt file and adding/editing gpu_mem=16 to the file.

Add support for cgroups​

Raspberry Pi OS does not have cgroups enabled.
K3s needs cgroups to be able to start the systemd service.

cgroupscan be enabled by appending cgroup_memory=1 cgroup_enable=memory to the end of the line in /boot/cmdline.txt.

You can do this with nano -
Then add to the bottom - 

sudo nano /boot/cmdline.txt

Save and exit - 

ctrl+o
ctrl+x

Rename System​

This is basically to allow us to easily identify the device on the network & in the cluster, through its hostname.
In same raspi-config as previous step:

  1. System Options
  2. Hostname
  3. Type in new hostname
  4. Finish

I would recommend a logical naming convention for cluster nodes, that go up sequentially.
Such as -

  • RPi-K3s-Node01
  • RPi-K3s-Node02
  • RPi-K3s-Node03
tip

You can pre-set the system names in the advanced options menu of Raspberry Pi imager.

Step 4 - Install & Configure Log2RAM​

Log2RAM is a storage solution that allocates a small % of your physical RAM as RAM Cache, and uses it to store log data from the system, flushing to disk on a regular schedule.

This is important to have in place where the OS partition is on a storage device that has to do wear leveling, so SSDs & SDs.

On a RPi, its doubly important as MicroSD's do not have the endurance to have sustained log writing to the disk for long periods without eventually killing the MicroSD.
This site her has a good breakdown of what it does in practice.

Install Log2RAM​

echo "deb [signed-by=/usr/share/keyrings/azlux-archive-keyring.gpg] http://packages.azlux.fr/debian/ bullseye main" | sudo tee /etc/apt/sources.list.d/azlux.list  

sudo wget -O /usr/share/keyrings/azlux-archive-keyring.gpg  https://azlux.fr/repo.gpg  

sudo apt update && sudo apt install log2ram

Configure Log2RAM​

Increase RAM allocation​

sudo nano /etc/log2ram.conf

Change SIZE variable (line 8) to 128M.
Save and exit - 

ctrl+o
ctrl+x

Increase frequency of log flushing​

sudo systemctl edit log2ram-daily.timer

Add the below block below line 2, but above the warning that says "Lines below this comment will be discarded".
Due to the amount of logs that K3s can generate, this will ensure that the log drive does not fill up, by increasing the frequency of how often it flushes the data from RAM to disk. 

[Timer]
OnCalendar=*-*-* */12:00:00
Persistent=true

Install additional apps​

Run the following to add some additional apps to the base OS that will be needed later. 

sudo apt install open-iscsi -y

Step 5 - Configure 'Swappiness'​

Edit config file 

sudo nano /etc/sysctl.conf

Add to the bottom of the file - 

vm.swappiness=0

Save and exit - 

ctrl+o
ctrl+x
tip

You can also do this with a one-liner, sudo echo "vm.swappiness=0" >> /etc/sysctl.conf

Step 6 - Edit the Host file​

Next we edit the system host file so it has hard coded local DNS entries for key services, and each other.
Then add to the bottom - 

sudo nano /etc/hosts

Then add to the bottom - 

192.168.0.231 rpi-k8s-01  
192.168.0.232 rpi-k8s-02  
192.168.0.233 rpi-k8s-03  
192.168.0.234 rpi-k8s-04 
192.168.0.235 rpi-k8s-05 
192.168.0.236 rpi-k8s-06  
192.168.0.251 logserver  
192.168.0.250 storageserver

Edit the IPs and names accordingly.
Save and exit - 

ctrl+o
ctrl+x
tip

You can also do this with a one-liner too -
sudo echo "192.168.0.1 RPi-K8s-01" >> /etc/hosts
sudo echo "192.168.0.2 RPi-K8s-02" >> /etc/hosts
sudo echo "192.168.0.3 RPi-K8s-03" >> /etc/hosts
sudo echo "192.168.0.10 logserver" >> /etc/hosts
sudo echo "192.168.0.11 storageserver" >> /etc/hosts

Step 8 - Set static IP​

Taking the IP addresses you set in Step 6, we now need to give our nodes static IPs.
We can do this either on the node itself, or if your network has DHCP capabilities, use a DHCP reservation instead.

If you do it on the node itself, the guide here is very useful, but be sure to use the same IPs you chose in step 6.

Step 9 - Reboot​

Now you can reboot - 

sudo reboot

Next Step​

Next, go to the next step, installing K3s.
Or,
Go back to the index page.