Now that everything is ready, we can use ansible to bring up the cluster with kubespray. The cluster.yml playbook will check to make sure all the dependencies are present on the nodes, versions are correct, and will proceed to install kubernetes on the cluster, as defined by the hosts.yaml you’ve created. Move to the kubespray area, and run the cluster.yaml playbook:

cd ~/workspace/picluster
poetry shell
cd kubespray
ansible-playbook -i ../inventory/mycluster/hosts.yaml -u ${USER} -b -v --private-key=~/.ssh/id_ed25519 cluster.yml

It takes a long time to run, but has a lot to do! With the verbose flag, you can see each step performed and whether or not things were changed or not. At the end, you’ll get a summary, just like on all the other playbooks that were invoked. Here is the end of the output for a run, where I already had a cluster (so things were setup already) and just ran the cluster.yml playbook again.

PLAY RECAP ********************************************************************************************************************************************************************************
cypher                     : ok=658  changed=69   unreachable=0    failed=0    skipped=1123 rescued=0    ignored=0
localhost                  : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
lock                       : ok=563  changed=44   unreachable=0    failed=0    skipped=1005 rescued=0    ignored=0
mouse                      : ok=483  changed=50   unreachable=0    failed=0    skipped=717  rescued=0    ignored=0
niobi                      : ok=415  changed=37   unreachable=0    failed=0    skipped=684  rescued=0    ignored=0

Sunday 31 December 2023  10:10:12 -0500 (0:00:00.173)       0:21:31.035 *******
===============================================================================
container-engine/validate-container-engine : Populate service facts --------------------------------------------------------------------------------------------------------------- 99.19s
kubernetes-apps/ansible : Kubernetes Apps | Start Resources ----------------------------------------------------------------------------------------------------------------------- 46.85s
etcd : Reload etcd ---------------------------------------------------------------------------------------------------------------------------------------------------------------- 35.10s
etcd : Gen_certs | Write etcd member/admin and kube_control_plane client certs to other etcd nodes -------------------------------------------------------------------------------- 34.06s
kubespray-defaults : Gather ansible_default_ipv4 from all hosts ------------------------------------------------------------------------------------------------------------------- 27.37s
network_plugin/calico : Start Calico resources ------------------------------------------------------------------------------------------------------------------------------------ 26.65s
download : Download_file | Download item ------------------------------------------------------------------------------------------------------------------------------------------ 25.50s
policy_controller/calico : Start of Calico kube controllers ----------------------------------------------------------------------------------------------------------------------- 17.93s
network_plugin/calico : Check if calico ready ------------------------------------------------------------------------------------------------------------------------------------- 17.34s
kubernetes-apps/ansible : Kubernetes Apps | Lay Down CoreDNS templates ------------------------------------------------------------------------------------------------------------ 17.28s
etcd : Gen_certs | Gather etcd member/admin and kube_control_plane client certs from first etcd node ------------------------------------------------------------------------------ 16.50s
download : Download_file | Download item ------------------------------------------------------------------------------------------------------------------------------------------ 14.33s
download : Check_pull_required |  Generate a list of information about the images on a node --------------------------------------------------------------------------------------- 12.78s
container-engine/containerd : Containerd | restart containerd --------------------------------------------------------------------------------------------------------------------- 12.36s
download : Check_pull_required |  Generate a list of information about the images on a node --------------------------------------------------------------------------------------- 12.13s
etcd : Gen_certs | run cert generation script for etcd and kube control plane nodes ----------------------------------------------------------------------------------------------- 11.75s
download : Check_pull_required |  Generate a list of information about the images on a node --------------------------------------------------------------------------------------- 11.47s
download : Check_pull_required |  Generate a list of information about the images on a node --------------------------------------------------------------------------------------- 11.46s
network_plugin/calico : Calico | Create calico manifests -------------------------------------------------------------------------------------------------------------------------- 11.23s
download : Download_file | Download item ------------------------------------------------------------------------------------------------------------------------------------------ 10.81s

If things are broken, you’ll need to go back and fix them and try again. Once it is working, though, we can now get the kube configuration file, so that we can run kubectl commands (we installed kubectl on the Mac in step IV). I use a script (at ~/workspace/picluster) to make this easy to do:

../setup-kubectl.bash

The contents of the script are:

CONTROL_PLANE_NODE=cypher
CONTROL_PLANE_NODE_IP=10.11.12.198
ssh ${CONTROL_PLANE_NODE} sudo cp /etc/kubernetes/admin.conf /home/${USER}/.kube/config
ssh ${CONTROL_PLANE_NODE} sudo chown ${USER} /home/${USER}/.kube/config
mkdir -p ~/.kube
scp ${CONTROL_PLANE_NODE}:.kube/config ~/.kube/config
sed -i .bak -e "s/127\.0\.0\.1/${CONTROL_PLANE_NODE_IP}/" ~/.kube/config

You’ll need to change the CONTROL_PLANE_NODE with the name of one of the control plane nodes, and CONTROL_PLANE_NODE_IP with that node’s IP address. Once this command is run, the config file will be set up to allow the kubectl command to access the cluster.

Next up in the series will be adding shared storage, a load balancer, ingress, monitoring, etc. Below are some other operations that can be done for the cluster.

Upgrading Cluster

This is a two step process, depending on what version you want to get to with Kubernetes, and what release of kubespray you are running. Each release of kubespray will have a tag and will correspond to a kubernetes version. You can see the tags with:

git tag | sort -V --reverse
v2.23.1
v2.23.0
v2.22.1
v2.22.0
v2.21.0
...

Alternately, you can just use a specific commit or the latest on the master branch. Once you decide which tag/commit you want, you can do a checkout for that version:

git checkout v2.23.1
git checkout aea150e5d

For whichever tag/commit you use, you can find out the default kubernetes and calico plugin (what I chose for networking), by doing grep commands from the repo area (you can look at specific files, but some times these are stored in different places):

grep -R "kube_version: "
grep -R "calico_version: "

Please note that, with kubespray, you have to upgrade by major release, and cannot skip releases. So, if you want to go from tag v2.21.0 to v2.23.1, you would need to update to v2.22.0 or v2.22.1, and then v2.23.1.0. If you are using a commit, just see what the previous tag was for the commit and then update tags to that tag and then you’ll be all set.

Initially, I ended up using a non-tag version of kubespray because I wanted kubernetes 1.27, and the nearest release tag at the time was v2.22.1, which used kubernetes 1.26.5. I ended up using a commit on master that gave me 1.27.3.

As of this writing, the newest tag is v2.23.1, which is 9 weeks ago, uses kubernetes 1.27.7. I just grabbed the latest on master, which supports kubernetes 1.28.5 (you can see that in commit message):

git show HEAD:inventory/sample/group_vars/k8s_cluster/k8s-cluster.yml | grep kube_version
kube_version: v1.28.5

Granted, you may want to stick to tagged releases (it’s safer), or venture into newer versions, with newer kubernetes. However, you still need to update by a major release at a time with kubespray.

To update kubespray, from ~/workspace/picluster/kubespray/ I did the following:

• Saved my old inventory: mv ~/workspace/picluster/inventory/mycluster{,.save}
• Did a “git pull origin master” for the kubespray repo and checked out the version I wanted (either a tag, latest, etc).
• Copied the sample inventory: cp -r inventory/sample ../inventory/mycluster
• Updated files in ../inventory/mycluster/* from the ones in mycluster.save to get the customizations made. This includes hosts.yaml, group_vars/k8s_cluster/k8s-cluster.yml, group_vars/k8s_cluster/addons.yml, other_servers.yaml, and any other files you customized.
• I set the kubernetes_version in group_vars/k8s_cluster/k8s-cluster.yml to the version desired, as this was a customized item that was older.

In my case, the default calico version would be v3.26.4 (before I had v3.25.2 overridden), and kubernetes v1.28.5 (before I had v1.27.3).

Use the following command, to upgrade the cluster, using the new kubespray code and kubernetes version:

ansible-playbook -i ../inventory/mycluster/hosts.yaml -u ${USER} -b -v --private-key=~/.ssh/id_ed25519 upgrade-cluster.yml

When I did this, I ended up with Kubernetes 1.28.2, instead of the default 1.28.5 (not sure why). I ran the upgrade again, only this time I specified “kube_version: v1.28.5” in the ../inventory/mycluster/group_vars/k8s_cluster/k8s-cluster.yml as an override, but it still was using v1.28.2.

Ref: https://kubespray.io/#/docs/upgrades

Adding a node

I received another Raspberry PI 4 for Christmas and wanted to add it to the cluster. I followed all the steps in Part II to place the Ubuntu on the PI, Part III to repartition the SSD drive, Part IV to add the new host to hosts.yaml and then ran the ansible commands just for the node I was adding to setup the rest of the items needed.

To add a control plane node, update the inventory (adding the node definition, and adding the node name to the control plane list and list of nodes) and run the kubespray cluster.yml script:

ansible-playbook -i ../inventory/mycluster/hosts.yaml -u ${USER} -b -v --private-key=~/.ssh/id_ed25519 cluster.yml

Then, restart the nginx-proxy pod, which is the local proxy for the api server. Since I’m using containerd, run this on each worker node:

crictl ps | grep nginx-proxy | awk '{print $1}' | xargs crictl stop

To add a worker node, update the inventory (adding the node definition, and adding the node name to the node list) and run the kubespray scale.yml script:

ansible-playbook -i ../inventory/mycluster/hosts.yaml -u ${USER} -b -v --private-key=~/.ssh/id_ed25519 --limit=NODE_NAME scale.yml

Use the limit arg to not disturb the other nodes.

Ref: https://kubespray.io/#/docs/nodes

Tear Down Cluster

To tear down the cluster, you can use the reset.yml playbook provided:

ansible-playbook -i ../inventory/mycluster/hosts.yaml -u ${USER} -b -v --private-key=~/.ssh/id_ed25519 reset.yml

Side Bar

Old Tools…

On one attempt, after having updated the kubespray repo to the latest version, the cluster.yaml failed because ansible version I was using was too old:

TASK [Check 2.15.5 <= Ansible version < 2.17.0] *******************************************************************************************************************************************
fatal: [localhost]: FAILED! => {
    "assertion": "ansible_version.string is version(minimal_ansible_version, \">=\")",
    "changed": false,
    "evaluated_to": false,
    "msg": "Ansible must be between 2.15.5 and 2.17.0 exclusive - you have 2.14.13"
}

Doing a “poetry show”, I could see what I had for ansible and one of the dependencies, ansible-core:

ansible          7.6.0   Radically simple IT automation
ansible-core     2.14.13 Radically simple IT automation

To update, I used the command “poetry add ansible@latest”, which would reinstall the latest version and update all the dependencies:

Using version ^9.1.0 for ansible

Updating dependencies
Resolving dependencies... (0.3s)

Package operations: 0 installs, 2 updates, 0 removals

  • Updating ansible-core (2.14.13 -> 2.16.2)
  • Updating ansible (7.6.0 -> 9.1.0)

Writing lock file

If desired, you can do a “poetry search ansible” or “poetry search ansible-core” to see what the latest version is, and you can always specify exactly which version you want to install. That’s the beauty of poetry, in that you can fix specific versions of a package, so that things are repeatable.

Mismatched Calico/Kubernetes Versions

I had a case where my cluster was at kubernetes v1.27.3 and v3.25.2 Calico. The kubespray repo had a tag of v2.23.1, which called out v1.27.7 kubernetes and v3.25.2 Calico. Things were great.

I tried to update kubespray to latest on master branch, which defaults to kubenetes v1.28.5 and v3.26.4. However, I still had v3.25.2 Calico in my customizations (with kubernetes updated to call out v1.28.5). The cluster.yml playbook ran w/o issues, but the calico-node pods were not up and were in a crash loops. The install-cni container for a calico-node pod was showing an error saying:

Unable to create token for CNI kubeconfig error=serviceaccounts "calico-node" is forbidden: User "system:serviceaccount:kube-system:calico-node" cannot create resource "serviceaccounts/token" in API group "" in the namespace "kube-system"

Even though kubernetes v1.28.5 is supported by Calico v3.25.2, there was some incompatibility. I haven’t figured it out, but I saw this before as well, and the solution was to either use the versions called out in the commit being used for kubespray, or at least near that version for kubernetes. By using the default v3.26.4 Calico, it came up fine.

Also note that even though I specified kubernetes v1.28.5, in my customization (which happened to be the same as the default), I ended up with v1.28.2 (not sure why).

There are a bunch of ways to create a cluster (microk8s, k3s, KOps, kubeadm, kubespray,…) and after looking at a bunch of them, I decided to use kubespray (ref: https://kubespray.io/#/). I’m going to use my MacBook to drive all this, so I setup an environment on that machine with all the tools I needed (and more).

Getting The Provisioning System Ready

I created a directory ~/workspace/picluster to hold everything, and created a git repo so that I have a version controlled area to record all the changes and customizations I’m going to make. For the Mac, I used brew to install python3.11 (ref: https://www.python.org/downloads/) and poetry (ref: https://python-poetry.org/docs/) to create a virtual environment for the tools I use and to fix versions. Currently my poetry environment has:

[tool.poetry.dependencies]
python = "^3.11"
ansible = "7.6.0"
argcomplete = "^3.1.1"
"ruamel.yaml" = "^0.17.32"
pbr = "^5.11.1"
netaddr = "^0.8.0"
jmespath = "^1.0.1"

python is obvious and I’m fixing it to 3.11. ansible is the tool used to provision the nodes. argcomplete is optional, if you want to have command completion. ruamel-yaml is a YAM parser, pbr is used for python builds, netaddr is a network address manipulation lib for python, and jmespath is for JSON matching expression.

You can use any virtual environment tool you want to ensure that you have the desired dependencies. Under “poetry shell“, which creates a virtual environment I continues with the prep work for using kubespray. I installed helm, jq, and kubectl:

brew install helm
brew install jq
brew install wget
brew install kubectl

Note that, for kubectl, I really wanted v1.28, and specified by version (kubectl@1.28), however, when trying months later, that version appears to not be available, and now it will install 1.29).

Defining Your Inventory

I cloned the kubespray repo and then checked out the version I wanted.

git clone https://github.com/kubernetes-sigs/kubespray.git
git tag | sort -V --reverse
git checkout v2.23.1  # for example

The releases have tags, but you can chose to use any commit desired (or latest). Sometimes, there are newer versions used with commits after the release. For a specific commit, you can see what default Kubernetes version and Calico version are configured for the commit with:

grep -R "kube_version: "
grep -R "calico_version: "

You can override the values in inventory/sample/group_vars/k8s_cluster/k8s-cluster.yml, but make sure the kubernetes and calico versions are compatible. You can check at this Tigera link to see the kubernetes versions supported for a Calico release. I have run into some issues when trying a Calico/Kubernetes pair that was not called out in the kubespray configuration (see side bar in Part V).

With the kubespray repo, I copied the sample inventory to the current area (so that the inventory for my cluster is separate from the kubespray repo):

mkdir inventory
cp -r kubespray/inventory/sample/ inventory/mycluster/

They have a script that can be used to create the inventory file for the cluster. You can obtain it with::

wget https://raw.githubusercontent.com/kubernetes-sigs/kubespray/master/contrib/inventory_builder/inventory.py

Next, you can create a basic inventory by using the following command, using IPs that you have defined for each of your nodes. If you have four, like me, you could use something like this:

CONFIG_FILE=inventory/mycluster/hosts.yaml python3 inventory.py 10.11.12.198 10.11.12.196 10.11.12.194 10.11.12.192

This creates an inventory file, which is very generic. To customize it for my use, I changed each of the “node#” host names to the names I used for my cluster:

sed -i.bak 's/node1/mycoolname/g' inventory/mycluster/hosts.yaml

I kept the grouping of which nodes were in the control plane, however, later on, I want to have three control plane nodes set up. The last thing I did, was to add the following clause to the end of the file so that proxy_env was defined, but empty (note that it is indented two and four spaces):

  vars:
    proxy_env: []

Here is a sample inventory:

all:
  hosts:
    cypher:
      ansible_host: 10.11.12.198
      ip: 10.11.12.198
      access_ip: 10.11.12.198
    lock:
      ansible_host: 10.11.12.196
      ip: 10.11.12.196
      access_ip: 10.11.12.196
    mouse:
      ansible_host: 10.11.12.194
      ip: 10.11.12.194
      access_ip: 10.11.12.194
    niobi:
      ansible_host: 10.11.12.192
      ip: 10.11.12.192
      access_ip: 10.11.12.192
  children:
    kube_control_plane:
      hosts:
        cypher:
        lock:
    kube_node:
      hosts:
        cypher:
        lock:
        mouse:
        niobi:
    etcd:
      hosts:
        cypher:
        lock:
        mouse:
    k8s_cluster:
      children:
        kube_control_plane:
        kube_node:
    calico_rr:
      hosts: {}
  vars:
    proxy_env: []

There are some configurations in the inventory files that need to be changed. This may involve changing existing settings or adding new ones. In inventory/mycluster/group_vars/k8s_cluster/addons.yml we need to enable helm:

helm_enabled: true

In inventory/mycluster/group_vars/k8s_cluster/k8s-cluster.yml, set kubernetes version, timezone, DNS servers, pin Calico version, use Calico IPIP mode, increase logging level (if desired), use iptables, disable node local DNS (otherwise get error as kernel does not have dummy module). and disable pod security policy:

kube_version: v1.27.3

# Set timezone
ntp_timezone: America/New_York

# DNS Servers (OpenDNS - use whatever you want here)
upstream_dns_servers: [YOUR_ROUTER_IP]
nameservers: [208.67.222.222, 208.67.220.220]

# Pinning Calico version
calico_version: v3.25.2

# Use IPIP mode
calico_ipip_mode: 'Always'
calico_vxlan_mode: 'Never'
calico_network_backend: 'bird'

# Added debug
kube_log_level: 5

# Using iptables
kube_proxy_mode: iptables

# Must disable, as kernel on RPI does not have dummy module
enable_nodelocaldns: false

# Pod security policy (RBAC must be enabled either by having 'RBAC' in authorization_modes or kubeadm enabled)
podsecuritypolicy_enabled: false

BTW, if you want to run ansible commands on other systems in your network, you can edit inventory/mycluster/other_servers.yaml and add the host information there:

all:
  hosts:
    neo:
      ansible_host: 10.11.12.180
      ip: 10.11.12.180
      access_ip: 10.11.12.180
      ansible_port: 7666
    rabbit:
      ansible_host: 10.11.12.200
      ip: 10.11.12.200
      access_ip: 10.11.12.200
  vars:
    proxy_env: []

In this example, my_other_server is accessed on SSH port 7777, versus the default 22.

General Node Setup Steps

Kubespray uses ansible to communicate and provision each node, and ansible uses SSH. At this time, from your provisioning host, make sure that you can SSH into each node without a password. Each node should have your public SSH key in their ~/.ssh/authorized_keys file.

Ansible has a bunch of “playbooks” that you can run, so I looked around on the internet, found a bunch and placed them into a sub-directory called playbooks. Now is a good time to do some more node configuration, and make sure that ansible, the inventory file, and SSH are all setup correctly. It is way easier than logging into each node and making changes. And yes, I suspect one could put all this into one huge ansible playbook, but I like to do things one at a time and check that they work.

When we run a playbook, we’ll provide our private key for SSH access, turn on the verbose (-v) flag), and sometimes ask for privilege execution. I’ll show the command for both a single node (substitute the hostname for HOSTNAME) that is in the inventory, and for all hosts in the inventory. When the playbook runs, it will display the steps being performed, and with -v flag you can see if things are changed or not. At the end, it will show a summary of the playbook run. For example, here is the output of a “ping” to every node in the cluster:

cd ~/workspace/picluster
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/ping.yaml --private-key=~/.ssh/id_ed25519

PLAY [Test Ping] **************************************************************************************************************************************************************************

TASK [Gathering Facts] ********************************************************************************************************************************************************************
ok: [lock]
ok: [cypher]
ok: [niobi]
ok: [mouse]

TASK [ping] *******************************************************************************************************************************************************************************
ok: [niobi]
ok: [mouse]
ok: [cypher]
ok: [lock]

PLAY RECAP ********************************************************************************************************************************************************************************
cypher                     : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
lock                       : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
mouse                      : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
niobi                      : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

You’ll want to check the recap to see if there are any failures, and if there are, check above for the step and item that failed.

For the node preparation, the first item is a playbook to add your username to the sudo list, so that you don’t have to enter in a password, when running sudo commands:

Single node:
ansible-playbook -i "HOSTNAME," playbooks/passwordless_sudo.yaml -v --private-key=~/.ssh/id_ed25519 --ask-become-pass

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/passwordless_sudo.yaml -v --private-key=~/.ssh/id_ed25519 --ask-become-pass

The passwordless_sudo.yaml contains (change USER to the username you are using):

- name: Make users passwordless for sudo in group sudo
  hosts: all
  become: yes
  vars:
    node_username: "{{ lookup('env','USER') }}"
  tasks:
    - name: Add user to sudoers
      copy:
        dest: "/etc/sudoers.d/{{ node_username }}"
        content: "{{ node_username }}  ALL=(ALL)  NOPASSWD: ALL"

You’ll have to provide your password, so that it can change the sudo permissions (hence the –ask-become-pass argument).

Next, you can setup for secure SSH by disabling root login and password based login:

Single node:
ansible-playbook -i "HOSTNAME," playbooks/ssh.yaml -v --private-key=~/.ssh/id_ed25519

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/ssh.yaml -v --private-key=~/.ssh/id_ed25519

The ssh.yaml file has:

- name: Secure SSH
  hosts: all
  become: yes
  tasks:
    - name: Disable Password Authentication
      lineinfile:
        dest=/etc/ssh/sshd_config
        regexp='^PasswordAuthentication'
        line="PasswordAuthentication no"
        state=present
        backup=yes
      register: no_password
    - name: Disable Root Login
      lineinfile:
        dest=/etc/ssh/sshd_config
        regexp='^PermitRootLogin'
        line="PermitRootLogin no"
        state=present
        backup=yes
      register: no_root
    - name: Restart service
      ansible.builtin.systemd:
        state: restarted
        name: ssh
      when:
        - no_password.changed or no_root.changed

For the Raspberry PI, we want to configure the fully qualified domain name and hostname and update the hosts file. Note: I use <hostname>.home for the FQDN.

Single node:
ansible-playbook -i “cypher,” playbooks/hostname.yaml -v –private-key=~/.ssh/id_ed25519

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/hostname.yaml -v –private-key=~/.ssh/id_ed25519

The hostname.yaml file is:

- name: FQDN and hostname
  hosts: all
  become: true
  tasks:
    - name: Configure FQDN and hostname
      ansible.builtin.lineinfile:
        path: /boot/firmware/user-data
        regexp: "{{ item.regexp }}"
        line: "{{ item.line }}"
      loop:
        - { regexp: '^fqdn\: ', line: 'fqdn: {{ ansible_hostname }}.home' }
        - { regexp: '^hostname\:', line: 'hostname: {{ ansible_hostname }}' }
      register: hostname
    - name: Make sure hosts file updated
      ansible.builtin.lineinfile:
        path: /etc/hosts
        regexp: "^127.0.1.1"
        line: "127.0.1.1 {{ ansible_hostname }}.home {{ ansible_hostname }}"
      register: hosts
    - name: Reboot after change
      reboot:
      when:
        - hostname.changed or hosts.changed

I place a bunch of tools on the nodes, but before doing so, update the OS. I used a ansible role for doing reboots by pulling this down with the following command run from the ~/workspace/picluster/ area:

git clone https://github.com/ryandaniels/ansible-role-server-update-reboot.git roles/server-update-reboot

The syntax of this is a bit different for this command

Single node:
ansible-playbook -i "HOSTNAME," playbooks/os_update.yaml --extra-vars "inventory=all reboot_default=false proxy_env=[]" --private-key=~/.ssh/id_ed25519

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/os_update.yaml --extra-vars "inventory=all reboot_default=false" --private-key=~/.ssh/id_ed25519

Granted, I’ve had times where updates required some prompting and I don’t think the script handled it. You can always log in to each node and do it manually, if desired. The os_update.yaml will update each system once at a time:

- hosts: '{{inventory}}'
  max_fail_percentage: 0
  serial: 1
  become: yes
  roles:
    - server-update-reboot

Tools can now be installed on nodes by using:

Single node:
ansible-playbook -i "HOSTNAME," playbooks/tools.yaml -v --private-key=~/.ssh/id_ed25519

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/tools.yaml -v --private-key=~/.ssh/id_ed25519

Here is what the script installs. Feel free to add to the list, and remove emacs and ripgrep (tools I personally like):

- name: Install tools
  hosts: all
  vars:
    host_username: "{{ lookup('env','USER') }}"
  tasks:
    - name: install tools
      ansible.builtin.apt:
        name: "{{item}}"
        state: present
        update_cache: yes
      loop:
        - emacs
        - ripgrep
        - build-essential
        - make
        - nfs-common
        - open-iscsi
        - linux-modules-extra-raspi
      become: yes
    - name: Emacs config
      copy:
        src: "emacs-config.text"
        dest: "/home/{{ host_username }}/.emacs"
    - name: Git config
      copy:
        src: "git-config.text"
        dest: "/home/{{ host_username }}/.gitconfig"

In the playbooks area, I have an emacs-config.text with:

(global-unset-key [(control z)])
(global-unset-key [(control x)(control z)])
(global-set-key [(control z)] 'undo)
(add-to-list 'load-path "~/.emacs.d/lisp")
(require 'package)
(add-to-list 'package-archives
  '("melpa" . "http://melpa.milkbox.net/packages/") t)
(setq frame-title-format (list '(buffer-file-name "%f" "%b")))
(setq frame-icon-title-format frame-title-format)
(setq inhibit-splash-screen t)
(global-set-key [f8] 'goto-line)
(global-set-key [?\C-v] 'yank)
(setq column-number-mode t)

And a git-config.text with:

[user]
	name = YOUR NAME
	email = YOUR_EMAIL@ADDRESS
[alias]
	qlog = log --graph --abbrev-commit --pretty=oneline
	flog = log --all --pretty=format:'%h %ad | %s%d' --graph --date=short
	clog = log --graph --pretty=\"tformat:%C(yellow)%h%Creset %Cgreen(%ar)%Creset %C(bold blue)<%an>%Creset %C(red)%d%Creset %s\"
	lg = log --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %C(green)%an%Creset %Cgreen(%cr)%Creset' --abbrev-commit --date=relative
[gitreview]
	username = YOUR_USERNAME
[core]
	pager = "more"
	editor = "emacs"
[color]
  diff = auto
  status = auto
  branch = auto
  interactive = auto
  ui = true
  pager = true

Raspberry PI Specific Setups

For the configuration of the UCTRONICS OLED display and enabling the power switch to do a controlled shutdown, we need to place the sources on the node(s) and build them for that architecture. Before starting, get the sources:

cd ~/workspace
git clone https://github.com/pmichali/SKU_RM0004.git
cd picluster

Note: I forked the manufacturer’s repo and just renamed the image for now. Later, the manufacturer added a deployment script, but I’m sticking with manual install and using Ansible to set things up.

Next, use this command:

Single node:
ansible-playbook -i "HOSTNAME," playbooks/uctronics.yaml -v --private-key=~/.ssh/id_ed25519

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/uctronics.yaml -v --private-key=~/.ssh/id_ed25519

The uctronics.yaml contains:

- name: UCTRONICS Hardware setup
  hosts: all
  become: true
  tasks:
    - name: Enable OLED display and power switch
      ansible.builtin.lineinfile:
        path: /boot/firmware/config.txt
        regexp: "{{ item.regexp }}"
        line: "{{ item.line }}"
      loop:
        - { regexp: '^dtparam=i2c_arm=on', line: 'dtparam=i2c_arm=on,i2c_arm_baudrate=400000' }
        - { regexp: '^dtoverlay=gpio-shutdown', line: 'dtoverlay=gpio-shutdown,gpio_pin=4,active_low=1,gpio_pull=up'}
      register: hardware
    - name: Get sources
      copy:
        src: "~/workspace/SKU_RM0004"
        dest: "/root/"
      register: files
    - name: Check built
      stat:
        path: /root/SKU_RM0004/display"
      register: executable
    - name: Build display code
      community.general.make:
        chdir: "/root/SKU_RM0004/"
        make: /usr/bin/make
        target: oled_display
      when:
        - files.changed or not executable.stat.exists
      register: built
    - name: Check installed
      stat:
        path: /usr/local/bin/oled_display
      register: binary
    - name: Install display code
      ansible.builtin.command:
        chdir: "/root/SKU_RM0004/"
        cmd: "/usr/bin/install -m 755 oled_display /usr/local/bin"
      when:
        - built.changed or not binary.stat.exists
      register: installed
    - name: Service script
      copy:
        src: "oled.sh"
        dest: "/usr/local/bin/oled.sh"
        mode: 0755
      register: oled_shell
    - name: Service
      copy:
        src: "oled.service"
        dest: "/etc/systemd/system/oled.service"
        mode: 0640
      register: oled_service
    - name: Reload daemon
      ansible.builtin.systemd_service:
        daemon_reload: true
        name: oled
        enabled: true
        state: restarted
      when:
        - installed.changed or oled_shell.changed or oled_service.changed
    - name: Reboot after change
      reboot:
      when:
        - hardware.changed

This uses oled.sh in the playbooks area:

#!/bin/bash
echo "oled.service: ## Starting ##" | systemd-cat -p info
/usr/local/bin/oled_display

And oled.service for the service:

[Unit]
Description=OLED Display
Wants=network.target
After=syslog.target network-online.target
[Service]
Type=simple
ExecStart=/usr/local/bin/oled.sh
Restart=on-failure
RestartSec=10
KillMode=process
[Install]
WantedBy=multi-user.target

Next up is to setup cgroups for the Raspberry PI with the command:

Single node:
ansible-playbook -i "HOSTNAME," playbooks/cgroups.yaml -v --private-key=~/.ssh/id_ed25519

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/cgroups.yaml -v --private-key=~/.ssh/id_ed25519

The cgroups.yaml has:

- name: Prepare cgroups on Ubuntu based Raspberry PI
  hosts: all
  become: yes
  tasks:
    - name: Enable cgroup via boot commandline if not already enabled
      ansible.builtin.lineinfile:
        path: /boot/firmware/cmdline.txt
        backrefs: yes
        regexp: '^((?!.*\bcgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory swapaccount=1\b).*)$'
        line: '\1 cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory swapaccount=1'
      register: cgroup
    - name: Reboot after change
      reboot:
      when:
        - cgroup.changed

The following will setup load the overlay modules, setup iptables for bridged traffic, and will allow IPv4 forwarding.

Single node:
ansible-playbook -i "HOSTNAME," playbooks/iptables.yaml -v --private-key=~/.ssh/id_ed25519

All nodes:
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/iptables.yaml -v --private-key=~/.ssh/id_ed25519

The iptables.yaml contains:

- name: Prepare iptables on Ubuntu based Raspberry PI
  hosts: all
  become: yes
  tasks:
    - name: Load overlay modules
      community.general.modprobe:
        name: overlay
        persistent: present
    - name: Load br_netfilter module
      community.general.modprobe:
        name: br_netfilter
        persistent: present
    - name: Allow iptables to see bridged traffic
      ansible.posix.sysctl:
        name: net.bridge.bridge-nf-call-iptables
        value: '1'
        sysctl_set: true
    - name: Allow iptables to see bridged IPv6 traffic
      ansible.posix.sysctl:
        name: net.bridge.bridge-nf-call-ip6tables
        value: '1'
        sysctl_set: true
    - name: Allow IPv4 forwarding
      ansible.posix.sysctl:
        name: net.ipv4.ip_forward
        value: '1'
        sysctl_set: true

Tools For Cluster Nodes

With ansible, you can do a variety of operations on the nodes of the cluster. One is to ping nodes. You can do this for other systems in your network, if you set up the other_servers.yaml file:

To ping cluster...
ansible-playbook -i inventory/mycluster/hosts.yaml playbooks/ping.yaml -v --private-key=~/.ssh/id_ed25519

To ping other servers...
ansible-playbook -i inventory/mycluster/other_servers.yaml playbooks/ping.yaml -v --private-key=~/.ssh/id_ed25519

The ping.yaml script is pretty simple:

- name: Test Ping
  hosts: all
  tasks:
  - action: ping

You can make other scripts, as needed, like the o_update.yaml shown earlier on this page. At this point, we are ready to cross our fingers and bring up the Kubernetes cluster in Part V.

Side Bar

If during some of the UCTRONICS setup steps, I2C is not enabled and OLED display does not work, you can do these steps (ref: https://dexterexplains.com/r/20211030-how-to-install-raspi-config-on-ubuntu):

In a browser, go to https://archive.raspberrypi.org/debian/pool/main/r/raspi-config/

Get the latest version with (for example):

wget https://archive.raspberrypi.org/debian/pool/main/r/raspi-config/raspi-config_20230214_all.deb 

Install supporting packages:

sudo apt -y install libnewt0.52 whiptail parted triggerhappy lua5.1 alsa-utils

Fix any broken packages (just in case):

sudo apt install -fy

And then install the config util:

sudo dpkg -i ./raspi-config_20230214_all.deb

Run it with “sudo raspi-config” and select interface options, and then I2C, and then enable. Finally, do a “sudo reboot”.

OK, I probably didn’t need to do this, but I thought it may be nice to have separate partitions for logging files, OS, user area, and for “data”, which was going to be where shared disk space would come from. In any case, here are the gruesome details of what I did, for those interested…

Here is the layout that I was interested in doing:

Partition	Purpose
/dev/sda1	Unaltered original boot partition, about 256-512 MB.
/dev/sda2	Root partition setup for 100GB.
/dev/sda3	Will be /var and setup for 90GB.
/dev/sda5	For /tmp, limited to 2GB.
/dev/sda6	For /home dir, using 8GB.
/dev/sda7	Mounted as /var/lib/longhorn to be used for cluster shared storage. Rest of disk space.

First, I used my SD card that had Ubuntu OS on it and inserted that into the powered off system. I disconnected the network interface, so the “host” on the SD card would not conflict with systems already deployed. I ensured that the keyboard and HDMI display were connected, because all the work would need to be done from the local console.

Next, I unplugged the USB jumper that connects the SSD drive to the Raspberry PI4. I booted the system, and it looked for USB drive and then eventually SD drive and booted. It took a while, because I had the network disconnected. If you have a unique hostname/IP setup on the SD card, you could likely leave the network connected (and could paste in commands from this blog using an SSH connection).

Once up and I logged in, I inserted the USB jumper, so that the SSD drive is seen as an external drive. The SD card appears as /dev/mmcblk0p1 and /dev/mmcblk0p2 for the “fd” command, but the SSD drive is not there. I did a “sudo su”, as there are several commands to run as root. When I do “fdisk -l”, I can see the SSD drive as /dev/sda.

The first thing to be done, is to check the file system(otherwise the mount will fail and fsck cannot be run to fix mismatched free blocks in partition table) and then resize /dev/sda2:

e2fsck -f /dev/sda2
resize2fs /dev/sda2 100G

Next, run “fdisk /dev/sda” and use the “p” command to see the current partitions. There should be /dev/sda1 as a 256-512MB partition and /dev/sda2 with the remainder of the space of the drive. Delete partition #2 using the “d” command and “2”.

Created a new primary partition with “n”, “p”, “2”(default). Accepted the default FIRST sector, and for the LAST sector, enter “+100G”. When asked if the ext4 signature should be removed, you can enter “N”.

Create another new primary partition, “n”, “p”, “3”, accepted the default FIRST sector, and used “+90GB” for the LAST sector. That’s it for primary partitions, so we’ll now create an extended partition #4 with “n”, “e”, and accept the defaults. That gives around a 741-743 GB partition.

Now, you can create logical partitions with “n”, accepting the FIRST sector, and specifying the size as the LAST sector. We’ll create partition #5 that is “+2G”, partition #6 that is “+8G”, and finally partition #7 that accepts the defaults for FIRST and LAST to use the rest of the disk (about 730GB).

If you make any mistakes, you can do a “p” command to see the partitions, use the “d” command to delete mistakes, and then recreate the partitions as needed. This is all in memory for now. I print out the partitions one more time to make sure they look OK:

Command (m for help): p
Disk /dev/sda: 931.51 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: 2115
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 33553920 bytes
Disklabel type: dos
Disk identifier: 0x5036de4e

Device     Boot     Start        End    Sectors   Size Id Type
/dev/sda1  *         2048     526335     524288   256M  c W95 FAT32 (LBA)
/dev/sda2          526336  210241535  209715200   100G 83 Linux
/dev/sda3       210241536  398985215  188743680    90G 83 Linux
/dev/sda4       398985216 1953525167 1554539952 741.3G  5 Extended
/dev/sda5       398987264  403181567    4194304     2G 83 Linux
/dev/sda6       403183616  419960831   16777216     8G 83 Linux
/dev/sda7       419962880 1953525167 1533562288 731.3G 83 Linux

When things look OK, use the “w” command to write the partition table. Finally, use the “partprobe /dev/sda” command. I did a “shutdown -h 0”, removed the SD card, and reconnected the ethernet cable, and powered the Pi back on. You can ssh in and will see /dev/sda1 and /dev/sda2 with the desired sizes. Do “sudo su” so that you can run several commands as root.

Now it is time to set the partition types for all the other partitions:

mkfs -t ext4 /dev/sda3
mkfs -t ext4 /dev/sda4
mkfs -t ext4 /dev/sda5
mkfs -t ext4 /dev/sda6
mkfs -t ext4 /dev/sda7

Now we want to move some filesystems over to the new partitions. Create mount points and mount most of the new partitions:

mkdir -p /mnt/home /mnt/tmp /mnt/root /mnt/var
mount /dev/sda2 /mnt/root
mount /dev/sda3 /mnt/var
mount /dev/sda5 /mnt/tmp
mount /dev/sda6 /mnt/home

Use rsync to move things over from the current file system:

rsync -aqxP /mnt/root/var/* /mnt/var
rsync -aqxP  /mnt/root/tmp/* /mnt/tmp
rsync -aqxP  /mnt/root/home/* /mnt/home

The originals can now be removed:

cd /mnt/root
rm -rf var home tmp
cd

Using the “blkid” command, you can see the UUIDs for each of the new partitions. Edit /etc/fstab and add on the new mount points with their corresponding UUIDs:

UUID=W /var        ext4    defaults        0       2
UUID=X /tmp	      ext4    defaults	      0	      2
UUID=Y /home	      ext4    defaults	      0	      2
UUID=Z /var/lib/longhorn ext4    defaults	      0	      2

Where W is the UUID for /dev/sda3, X is the UUID for /dev/sda5, Y is the UUID for /dev/sda6, and Z is for /dev/sda7.

Finally, you can unmount all the partitions with the following and then reboot the system and check that the partitions are OK:

umount /dev/sda2 /dev/sda3 /dev/sda5 /dev/sda6

Not that you will have to give it time to shutdown and then restart. You can check the console with monitor attached. Mine took quite a while, I think because it was wrapping up upgrades from “sudo apt-get update -y && sudo apt-get upgrade -y” that I had done earlier. Just be patient.

After the system rebooted, I could see the partitions are mounted with “df -h”:

Filesystem      Size  Used Avail Use% Mounted on
tmpfs           781M  3.0M  778M   1% /run
/dev/sda2        99G  2.1G   93G   3% /
tmpfs           3.9G     0  3.9G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/sda6       7.8G  1.4M  7.4G   1% /home
/dev/sda3        89G  1.7G   82G   3% /var
/dev/sda5       2.0G   96K  1.8G   1% /tmp
/dev/sda1       505M  125M  381M  25% /boot/firmware
tmpfs           781M  4.0K  781M   1% /run/user/1000

Side Note

One thing to note with the UCTRONICS OLED status display and the repartitioning. The app that controls the display reports disk usage at 107%. I haven’t looked at it yet, but whatever it is using to determine disk space is not accounting for the change due to partitioning (it was fine before the partitioning). Fortunately, it is a simple Python app and the source is provided, so I can make some changes, maybe to report multiple “partitions”.

Assembly and OS Install

For the very first PI4 that I bought, I got the CANA kit, so it had a plastic enclosure, power adapter with switch, and 126 GB SD card. With this system I connected a mouse, keyboard, and HDMI monitor, and used the Raspberry PI imager app on my MacBook and installed Ubuntu server (22.04) on the SD card. I booted up and made sure everything worked.

Since I’m using these UCTRONICS trays, I would follow these steps to partially assemble the unit. I’d connect the SSD drive’s SATA connector to the SATA shield card, and screw the SSD card to the side of the tray. Next, I installed the SD adapter into the SATA shield card. I aligned the Raspberry PI4 onto the posts and screwed it on using the threaded standoffs for the PoE+ hat. I inserted the SD adapter into the SD slot of the PI, connected the OLED and power switch cables from the SATA shield card to the front panel. Lastly, I would connect the USB jumper from the SATA shield card to the Raspberry PI4 card for SSD drive connections.

I reused the power supply from my CANA kit, and connected the display and keyboard to the Raspberry PI. I think I could connect power to either the USB-C connector on the PI or on the SATA shield card. An alternative would be to attach the PoE+ hat, but then I’d have to connect ethernet to the PoE+ powered hub, and that was down in the rack, where I didn’t have an HDMI monitor. So I skipped that part, as I was doing this in the study. I connected ethernet cable and powered on the unit. The RPI will display an install screen, where you can press SHIFT key to cause net boot.

This will download the installer image and then restart. You’ll eventually get an installer screen like what the PI imager has on the Mac/PC. It is easiest to use a mouse, but if you don’t have one, you can press the tab button to advance field, and enter to select.

You’ll want to select the model of Raspberry PI (4), select the OS (I used Ubuntu 23.10 64 bit – in the past it was 22.04), and then select the storage device.

You should see the SSD drive listed (Samsung 1TB drive in my case), and select it. Click the next button, and select to edit the configuration. Enter the host name, enabled SSH with password authentication (for now), and selected a username and simple password (for now). I set the time zone as well. Here is an (older installer) screen shot of some settings.

Lastly, click on SAVE, click on YES to use the changes, and then click on the WRITE button. Again, here is an older screen shot, where there was no PI model button, and the configuration (gear icon) was on the same screen.

While the installer was running, I checked on my router for the hostname, and made a DHCP reservation for the final desired IP I wanted for that system. I also created a HOSTNAME.home DNS entry for this node.

At one point, it rebooted and eventually displayed that cloud init was done. I pressed ENTER and was able to log in. I shut down the system, and then started it back up, so that it would pickup the desired IP address that I setup on my router.

Node Setup

To make setup easier, I created an SSH key on this system, so that I could SSH in from my MacBook and do all the rest from there, without needing the display and keyboard connected. I SSHed into the system, created a key with:

ssh-keygen -t ed25519

and then I copied the public key to all the other nodes and systems so that I can easily get into the system. I also added this new system to the ~/.ssh/config file that I use on other systems, so that I can ssh using the host name. I set the login password to what I really wanted. Make sure that you can ssh into each node, without using a password.

Rather than rely on a DHCP reservation, I changed the /etc/netplay/50-cloud-init.yaml to assign a static IP, set the router IP, and set DNS servers and domain name (I purchased a domain name and used dynamic DNS to point it to my router’s external IP – using the router’s capability to keep the dynamic IP updated). Here is an example 50-cloud-init.yaml:

network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      addresses:
        - 10.11.12.198/24
      routes:
        - to: default
          via: 10.11.12.1
      nameservers:
        addresses: [10.11.12.1, 208.67.220.220]
        search: [MY.DOMANNAME]

This was done on each Raspberry PI, followed by “sudo netplan apply” to update the node. Just be sure to do this via the console, otherwise you’ll loose connection, if done from an ssh session.

Of course, there are several other things that need to be set up on a Raspberry PI, like:

• Setting the domain name for the node.
• Setting up the OLED display and power switch, since I’m using UCTRONICS tray.
• Changing kernel settings.

However, since I’ll be using kubespray to provision the cluster, and kubespray uses ansible, there is the ability to use ansible playbooks to provision all the nodes in a more automated fashion on all nodes. This will be detailed in Part IV, but the next step (Part III) is to do some (optional) partitioning of the SSD drive.

Side Bar

Alternative to netbooting and imaging

On some older units, I went through all sorts of contortions, to install an OS on the SD card using the Raspberry PI imager on my MacBook, booting, updating the rpi-eeprom, setting things up to net boot. There is a bootconfig.txt file that can be used to update the bootload for enabling net boot. I had this entry in there:

BOOT_ORDER=0xf241          SD(1), USB(4), network(2), retry each (f).

Though I’ve seen 0x41 as well. It was really messy. This new loader is much easier.

My SSD drive is not seen at netboot!

I hit a case with some newer SSD drives (a Crucial 2TB BX500 drive), where the drive did not show up in the installer’s list of storage devices to select. To get around this I had to do the following…

I attached the SSD drive to my Mac, using a SATA III adapter, and used the Raspberry PI imager to image the disk (using the same settings as explained above).

Then, I attached the SSD drive to the Raspberry PI’s USB3 port (with the UCTRONICS I installed the drive in the tray, connected to SATA Shield card, and used the provided USB3 jumper. I made sure there was no SD card installed, connected an Ethernet cable and started up the Raspberry PI, making sure it booted from the SSD card.

I have had cases where I had to boot from the SD card running Raspberry PI OS (imaged on a Mac or via net booting the RPI), and run these commands, to update the OS, EEPROM, and bootloader…

sudo apt update
sudo apt full-upgrade
sudo rpi-update
sudo rpi-eeprom-update -d -a

I then rebooted, so that the new firmware was activated, and then tried to boot using the SD card and see if the SSD drive was visible (sudo fdisk -l), and then boot without the SD card, hoping it would boot from the SSD drive.

I also tried netbooting to the installer, and instead of choosing an OS, I chose Utility Apps, Bootloader, and picked the option to boot to USB. I wrote that to the SD storage device, it rebooted, and I checked to see if it booted to the SSD. If it did, I would shutdown and restart, without the SD card.

It was a bit of a mess trying to get it working. This happened recently, when I wanted to setup two more PI 4s. One I had to go through these hoops, and the other one worked, after I imaged the SSD on the Mac. I guess the PI4 bootloader should boot from USB, out of the box. For some reason, I hit one that did not.

Goals

Currently, I have a few of old tower based Linux servers, running services (VPN, file server, Emby music server, a custom app for monitoring my photovoltaic system, etc). I had started to adapt several of these to run in containers, so that I could move them around, if a system failed, especially since the systems were getting quite old.

In addition, I started to buy some Raspberry PIs so that I had newer technology and hosts that used much less power than my old gear, and I could place these containers on the PIs.

Since I worked with Kubernetes development for several years, before retiring, I decided to build a cluster so I had a way to spread the workload, easily move pods around upon failures, monitor and manage the system, and scale it out as I get more Raspberry PIs.

For the initial design, I have five Raspberry PIs right now, though one is currently hosting a bunch of containers. Plan was to put four of them into service right now, and then once I have my containers migrated over to the cluster, I can add the fifth system. I just got a sixth one for Christmas, so I’ll be adding that in soon.

General Design

For the hardware, I’m using Raspberry PI 4s with 8 GB RAM (~$85 each), and I have the PoE+ Hats (~$28), so that I can power them off of the PoE based ethernet hub I have (LinkSys LGS116P 8 regular ports, 8 PoE ports ~$120). I purchased a bunch of Samsung 1 TB SSD drives (870 EVO ~$50). Probably should have gotten 2 TB or larger.

I found a really cool product from UCTRONICS (model B0B6TW81P6 ~$290), which consists of a 1U rack mounted enclosure that holds four Raspberry PI4s, each in a removable tray. There are two fans inside as well. Since I needed one or two more PIs, I also found just a face plate (model RM1U ~ $11) and individual tray units (RM1U-3 ~$76 each). Here is a picture of the enclosure on the bottom, and the face plate on the top.

Each of the tray units have a “SATA shield” logic board with SATA connector for the SSD drive on the bottom, a USB connector on the top that can be connected to the USB3 port of the PI using the provided connector and a jumper.

There is a front panel with a LCD that can display IP address, CPU temp, disk usage, and RAM usable (small python app that can be tweaked). There are SD and SSD activity LEDs on the shield card that show, and they provide a jumper cable for the SD card of the PI so that it is accessible from the front panel (via the shield card). Lastly, there is a power switch, so that you can do a clean shutdown.

There is room for the PI’s PoE Hat and a fan connector on the shield card, so that you can attach one of the fans in the enclosure to one of the PIs. The face plate is made out for a Model 4B PI. the enclosure is pricey, but a really great way to place these into a rack, have a SSD drive connected, and be able to cleanly shutdown the units.

The RM1U is not enclosed, and there are no fans, but I wasn’t concerned, as this unit would be in the basement, which is cool year round. I don’t know whether UCTRONICS will make something for the Raspberry PI 5s or how long they will make these rack mounts and enclosures, but it was a nice way for me to bundle things up.

For each of the Raspberry PIs, they will have a fixed IP address and a unique name (versus having node1, node2,…). I chose to have my router reserve IP addresses, outside of the range used for DHCP. Alternately, you could configure each PI with a static IP address.

Part II will discuss how to prepare the PIs for cluster use.