More Power! Adding nodes to cluster

I’ll document the process I used to add two more Raspberry Pi 4s to the cluster that I’ve created in this series.

Preparing The PIs

With two new Raspberry PI 4s, PoE+ hats, SSD drives (2 TB this time), and two more UCTRONICS RM1U-3 trays each with an OLED display, power button, SATA Shield card, and USB3 jumper, I set out to assemble the trays and image them with Ubuntu.

Everything went well, assembling the trays with the Raspberry PIs. In turn, I connected a keyboard, HDMI display, Ethernet cable, and power adapter (as I don’t have PoE hub in my study). Once booted, I followed the steps in Part II of the series, however there were some issues getting the OS installed.

First, the Raspberry PI Imager program has been updated to support PI 5s, so there were multiple menus, tabbed fields, etc. I decided to connect a mouse to the Raspberry PI, rather then enter a maze of tabs and enters and arrows to try to navigate everywhere.

Second, when I went to select the Storage Device, the SSD drive was not showing up. I didn’t know if this was an issue with the UCTRONICS SATA Shield, the different brand of drive, the larger capacity, the newer installer, or the Raspberry PI itself. I did a bunch of different things to try to find out the root cause, and finally found out that to make this work, I needed to image the SSD drive using the Raspberry PI Imager on my Mac, using a SATA to USB adapter, and then place it into the UCTRONICS tray along with the Raspberry PI and it would then boot to the SSD drive.

Third, for one of the two Raspberry PIs, this still did not work, and I ended up installing the Raspberry PI OS on an SD card, update the EEPROM and bootloader, and then net booted the Raspberry PI Installer, and then I was able to get the Raspberry PI to boot from the SSD drive. Probably a good idea to update the EEPROM and bootloader to the latest anyway.

Initial Setup

Like done in Part II of the series, I picked IP addresses for the two units, added their MAC addresses into my router so that those IPs were reserved, added the host names to my local DNS server, and create SSH keys for each and used “ssh-copy-id” to copy those keys to all the other nodes and my Mac, and vice versa. Connectivity was all set.

I decided NOT to do the repartitioning mentioned in Part III, and instead leave the drive as one large 2TB (1.8TB actually) drive. My hope is that with Kubernetes, I can monitor problems, so if I see log files getting out of hand, I can deal with it, rather than having fixed paritions for /tmp, /var, /home, etc.  I did create a /var/lib/longhorn directory – not sure if Longhorn would create this automatically.

Node Prep

With SSH access to each of the PIs, I could run through the same Ansible scripts that were used to setup all the other nodes as outlined in Part IV. Before running the scripts, I added the two nodes (morpheus, switch) to the hosts.yaml file in the inventory as worker nodes. There are currently, three master nodes, and four worker nodes.

When running these ansible scripts, I specified both hosts at once, rather than doing one at a time. For example:

cd ~/workspace/picluster
ansible-playbook -i "morpheus,switch" playbooks/passwordless_sudo.yaml -v --private-key=~/.ssh/id_ed25519 --ask-become-pass
ansible-playbook -i "morpheus,switch" playbooks/ssh.yaml -v --private-key=~/.ssh/id_ed25519
...

Now that the nodes are ready, they can be added to the cluster. For a control plane node, the cluster.yaml script is used:

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

Then, on each node, restart the NGINX proxy pod with:

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

In our case, these will be worker nodes, and would be added with these commands (using limit so other nodes are not affected:

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

These two nodes added just fine, with the Kubernetes version v1.28.5, just like the control plane node I added before (my older nodes are still v1.28.2, but not sure how to update them currently).