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Setting up Raspberry Pi for k3s#

Info

The following guide was heavily inspired / has snippets from this medium tutorial

Info

This guide assumes that you have already installed Ubuntu Server 21.04 on your Raspberry Pi

Logging into Raspberry Pi via SSH#

First things first, we need to login to our Raspberry Pi before doing anything. If this is your first time connecting to it, you'll need to connect your Raspberry Pi to your router via ethernet cable. We'll enable Wi-Fi later on in this section.

From your router's dashboard, you'll need to figure out which IP was assigned to the Raspberry Pi. The rest of this guide will assume the Raspberry Pi has an internal IP of 192.168.1.100 assigned to it via the router's DHCP.

Once you have your IP, time to SSH into this bad boy.

ssh [email protected]

Note

The default username and password for a fresh Ubuntu Server 21.04 install should be ubuntu / ubuntu. Don't worry, you'll be prompted to change this once you login for the first time.

Creating a new user#

Next up, let's create a new user that represents what this node will be doing. Assuming this Raspberry Pi will be our master node, we're going to create a new user called master

sudo adduser master

Let's now take all the groups that belonged to the ubuntu and add them to our newly created master user

# Running the following command while logged in as ubuntu
# should give you a list of all the groups the ubuntu user belongs to
groups

# Assign the same groups to master
sudo usermod -a -G adm,dialout,cdrom,floppy,sudo,audio,dip,video,plugdev,netdev,lxd master

Before deleting the ubuntu user, let's first make sure we can login with master

ssh [email protected]

If all goes well, we should can now safely remove the default user

sudo deluser --remove-home ubuntu

Change default hostname#

Let's change the hostname from the default to something more meaningful. Since this node will be our master node, we're going to change it to k8-m1

sudo hostnamectl set-hostname k8-m1

Also, since Ubuntu Server 21.04 uses cloud-init, we're going to have the following line in /etc/cloud/cloud.cfg

sudo nano /etc/cloud/cloud.cfg

# Change preserve_hostname to true
preserve_hostname: true

Securing SSH access#

Note

This section assumes that you're familiar with Key-Based authentication and that you already have a public / private key pair.

If not, you can generate one using the following instructions found in this link

Currently, anyone can ssh into our Raspberry Pi if they have our username and password. We're going to change this from password-based authentication to key-based authentication, for added security.

From your local machine, Let's copy our key to the master node

# This copies the public key (at ~/.ssh/id_k8-m1) to the master node
ssh-copy-id -i ~/.ssh/id_k8-m1 [email protected]

If successful, we should check if we can ssh into the master node with our key, without entering a password

ssh -i ~/.ssh/id_k8-m1 [email protected]

Next up, let's tighten up our ssh config so that we disable password login, enable key-based authentications and disable the ability to login as root

sudo nano /etc/ssh/sshd_config

Change the following lines

From:
#PermitRootLogin prohibit-password
#PasswordAuthentication yes
#PubkeyAuthentication yes

To:
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes

Finally, restart the sshd daemon so that the changes take effect

sudo systemctl restart sshd.service

Setup Linux Control Groups#

We need to setup Linux Control Groups that are used for resource monitoring and isolation that are needed by Kubernetes.

sudo nano /boot/firmware/cmdline.txt

Add the following at the end of the line

cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory

Adding password-less sudo to our user#

Note

We need our user to have password-less sudo so that k3sup would work correctly in the next step

# Run the following from your shell
sudo visudo

# Add the following at the end of the file
master ALL=(ALL) NOPASSWD:ALL

(Optional) Enable Wi-Fi on your Raspberry Pi#

Warning

It's recommended to connect the your cluster nodes via a wired connection for a general stability, and an overall better experience

This section will be about how to connect your Raspberry Pi to your network via WiFi1

First off, edit the following file

sudo nano /etc/netplan/50-cloud-init.yaml

Paste in the following under networks (don't forget to replace the SSID_name and WiFi_password placeholders)

wifis:
  wlan0:
    dhcp4: true
    optional: true
    access-points:
      "SSID_name":
        password: "WiFi_password"

Finally, apply the new netplan for it to take effect

sudo netplan apply

(Optional) Using a SSD with your RPI#

If you're planning on using a SSD with your RPI, it might be useful to follow the instructions found in this article since there's some quirks regarding which USB adapters work properly and some fixes that can be applied.

You might also want to look at enabling TRIM. This is OS dependent so I'll leave it up to you to find the appropriate guide.

  1. https://itsfoss.com/connect-wifi-terminal-ubuntu/ ↩

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