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Raspberry Pi hobby cluster

In this tutorial we are gonna try to setup a cluster in our home server built with raspberries.

In another post I'll describe how to configure a Kubernetes cluster in our raspberries.

Kubernetes is a container orchestration tool, it can do all of this:

  • Automatic bin packing

  • Self-healing

  • Horizontal scaling

  • Service discovery and Load balancing

  • Automated rollouts and rollbacks

  • Secrets and configuration management

  • Storage orchestration

  • Long running jobs

  • Batch execution

Requirements

SSH keys

We need a SSH key in order to connect to the cluster without having to type the password every time we access.

In case you don't have any, run this command and follow the steps.

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

Add the key to your ssh agent, assuming our keys generated are id_rsa and id_rsa.pub.

ssh-add ~/.ssh/id_rsa

You can find a more in depth explanation in this tutorial

Creating cloud-init-config

The flash command line utility, uses a cloud-init-conf in order to configure the debian system that it's going to be installed. We are gonna use hypriot debian, which is optimized for containers.

Let's generate the conf using a template I've created, remember to update the environment variables with your values.

Variable

Description

USERNAME

Username to login into the os

SSH_PUBLIC_KEY

A public key to log in without typing the password.

WIFI_SSID_NAME

The name of your wifi

WIFI_PASSWORD

Use wpa_passphrase SSID PASSWORD for preshared key

export USERNAME=willy
export WIFI_SSID_NAME="Bla bla"
export WIFI_PASSWORD="longandsecurepassword"
export WIFI_COUNTRY=NL
export TIMEZONE=$(curl -s https://ipapi.co/timezone)
export SSH_PUBLIC_KEY=$(cat ~/.ssh/id_rsa.pub)

curl -s https://gist.githubusercontent.com/Woile/51eca58047b6bd51c60eeae80d60ec14/raw/db05664b5e90a28472f139bc8757562c2ed13026/cloud-init-config-template.yaml | \
sed -e "s/\${USERNAME}/$USERNAME/" \
-e "s/\${WIFI_SSID_NAME}/$WIFI_SSID_NAME/" \
-e "s/\${WIFI_PASSWORD}/$WIFI_PASSWORD/" \
-e "s/\${WIFI_COUNTRY}/$WIFI_COUNTRY/" \
-e "s|\${TIMEZONE}|$TIMEZONE|" \
-e "s|\${SSH_PUBLIC_KEY}|$SSH_PUBLIC_KEY|" > cloud-init-config.yaml

Flashing SD cards

Insert the SD card and find it with df.

Flash the cloud-init-conf.yaml in all of your SD cards. It's important to change the hostname per raspberry. Pay attention to param --hostname.

For my 4 raspberries I am going to use these hostnames:

willy-1
willy-2
willy-3
willy-4

flash -f --hostname willy-1 --device <device_found_using_df> -u cloud-init-config.yaml hypriotos-rpi-v1.9.0.img pv

Example:

flash -f --hostname willy-1 --device /dev/mmcblk0 -u cloud-init-config.yaml hypriotos-rpi-v1.9.0.img pv

Plug the SD card on each raspberry and connect them to the wall.

Setting up the nodes

To find the IPs of your raspberries run:

# For Debian based OS
sudo apt-get install arp-scan
# For Mac
brew install arp-scan
ip a  # here found the interface, like wlp2s0
sudo arp-scan --interface=<your_interface> --localnet

Connect to each one of them using ssh <username>@<hostname>, because we previosuly added the ssh key, we should not need to type a passsword.

Execute on each node the next steps.

Reset password

Warning

This is an important step!

Update your user’s password with passwd. Remember that by default is hypriot.

Configure Firewall

For simplicity and in case you want to have a multi master cluster, we are gonna allow ports for master kubernetes and for kubernetes workers.

Run this as root typing sudo su

ufw --force reset  # ok
ufw allow ssh
ufw allow 6443 # Kubernetes API (master)
ufw allow 80  # HTTP
ufw allow 443  # HTTPS
ufw allow 8443  # kubectl proxy
ufw allow 10250  # Kubelet API (master and worker)
ufw allow 10251  # kube-scheduler (master)
ufw allow 10252  # kube-controller-manager (master)
ufw allow 2379:2380/tcp  # etcd server client API (master)
ufw allow 30000:32767/tcp  # NodePort Services** (worker)
ufw default deny incoming
yes | ufw enable

Ports used by kubernetes

Configuring master node

Choose one of the raspberries as the master, I use willy-1 as master.

Set static IP

Edit /etc/network/interfaces.d/eth0 and set it to

allow-hotplug eth0
iface eth0 inet static
address 10.0.0.1
netmask 255.255.255.0
broadcast 10.0.0.255
gateway 10.0.0.1

Reboot to claim the IP 10.0.0.1 in your internal cluster’s network (the switch network)

Allocate addresses to the worker nodes using DHCP

The cloud-init template already includes isc-dhcp-server

Edit /etc/default/isc-dhcp-server, comment out # INTERFACESv6="" and set INTERFACESv4="eth0"

Or run this

sudo sed -e '/INTERFACESv6=/ s/^#*/#/' -e 's/INTERFACESv4=""/INTERFACESv4="eth0"/g' -i /etc/default/isc-dhcp-server

Backup and edit /etc/dhcp/dhcpd.conf. Set it like this:

option domain-name "willy.home"; # Set a domain name, can be anything
option domain-name-servers 8.8.8.8, 8.8.4.4; # Use Google DNS by default, you can substitute ISP-supplied values here
subnet 10.0.0.0 netmask 255.255.255.0 { # We'll use 10.0.0.X for our subnet
    range 10.0.0.1 10.0.0.50;
    option subnet-mask 255.255.255.0;
    option broadcast-address 10.0.0.255;
    option routers 10.0.0.1;
}
default-lease-time 600;
max-lease-time 7200;
authoritative;

Restart service sudo systemctl restart dhcpcd.service

Now our master will start assigning addresses to the other nodes.

In case it’s not assigning IPs, try unplugging from the switch and restarting all the other nodes but the master. You can check the IPs by doing ip a or hostname -I, remember that this is the range range 10.0.0.1 10.0.0.50

Our cluster is set up now.

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