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4 node K3S on Oracle OCI Free Tier

This project allows you to deploy a real working k3s cluster on the Oracle's generous "always free" tier. You get 1 server and 3 dedicated workers. kubectl top nodes looks like this:

$ kubectl top nodes
NAME                     CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%   
inst-canri-k3s-workers   40m          4%     1000Mi          16%       
inst-ded0p-k3s-workers   41m          4%     914Mi           15%       
inst-ign06-k3s-workers   35m          3%     1133Mi          19%       
inst-nsvzh-k3s-servers   122m         12%    2232Mi          37%

This leaves around ~15gb of memory and most of the 3x ARM CPUs for you to play with. Not bad for free!

DISCLAIMERS:

  1. The Ampere A1 instance shape used in this project is eligible for the free tier. But I found it extremely difficult to deploy this project, with OCI reporting that these instances are at full capacity in my region. I also found it impossible to deploy an instance pool with more than 2 instances in it (which I wanted for my workers). I decided to upgrade my account (which requires a credit card). And just like that, I could reliably deploy all 4 instances, and the worker instance pool had no problem with 3x instances. So this project basically requires an upgraded OCI account with a credit card on it. (But it still shouldn't cost you anything)

  2. This is a brittle setup, because it deploys a single k3s server and 3x workers. I took this approach because I'm not going to run anything critical on it. That said, I have had 2 servers on OCI running for over 400 days with zero downtime, so that's good enough for me! I may tinker with this serup later, and perhaps try 3x servers and 1x dedicated worker, with workloads also runing on the servers. If you happen to use this project and decide to make that change yourself, please send me a pull request if it works!

Before you begin

Pre-requisites

  1. Oracle Cloud account (sign up here and upgrade to a paid account)
  2. Download and install the following:

Network Security

Some facts about OCI:

  • Security Lists apply to all VNICs in the VCN. We'll use that to allow ssh (port 22) access from our home IP address
  • Network Security Groups only affect resources they're attached to (eg: instances, load balancers)

Terraform

This project contains two modules:

  • network: deploys VCN, security groups and rules, load balancers etc
  • cluster: deploys instance pools for k3s server and workers

Once Kubernetes is running, it also deploys into it:

  • Longhorn (CSI)
  • Traefic ingress controller (installed automatically, using Helm)
  • Metrics Server (installed automatically, using kubectl apply)

Missing pieces...

To make it easier to deploy real stuff to the cluster, we still need:

  • cert-manager
  • external-dns
  • a domain!

However, I haven't gotten to this yet. Also, you might want to use HTTPS01 or DNS01 ACME challenges for cert manager, and you might have a totally different DNS provider. I might add my Cloudflare setup to this project, with example values.yaml files for cert-manager and external-dns helm charts.

Deploying it!

Create an env.auto.tfvars file

This file should be placed in the root of the project. Its contents will specific to your OCI account. Here's what I've got in mine (with totally fake details, of course):

compartment_ocid = "ocid1.tenancy.oc1..aaaaaaaaffdnionfsfnseifonvosfn32g4i3no6ih9gewenewowntio32nos"
tenancy_ocid     = "ocid1.tenancy.oc1..aaaaaaaaffdnionfsfnseifonvosfn32g4i3no6ih9gewenewowntio32nos"
user_ocid        = "ocid1.user.oc1..aaaaaaaabkc6lfmneesonfoinesiofnefiegbesuifbui3br3u69wet9wbt3"
fingerprint      = "1a:fe:ed:42:ba:5a:2b:91:aa:25:f9:4a:dd:8c:f6:96"
private_key_path = "/home/raffraffraff/.oci/oci_api_key.pem"
public_key_path  = "/home/raffraffraff/.ssh/id_ed25519.pub"
region           = "eu-amsterdam-1"

# Network config
availability_domain = "qhym:eu-amsterdam-1-AD-1"

# Cluster config
cluster_name     = "mylovelycluster"
os_image_id      = "ocid1.image.oc1.eu-amsterdam-1.aaaaaaaa72byfaddfn2wkdhhtgb7c7jjh5jfvri63vumfrafo2tvhdsny3pq"

Apply terraform

There's more to it than this, but basically...

terraform init
terraform plan
terraform app

Copy the kubeconfig from the server

When you terraform apply finishes, terraform will output a bunch of IP addresses (yeah, these are fake):

nlb_ip_address = "151.183.24.123"
servers_ips = [
  "151.182.123.14",
]
workers_ips = [
  "83.23.175.22",
  "151.181.208.130",
  "134.211.73.19",
]

So you just need to copy the /etc/rancher/k3s/k3s.yaml from the server to your machine and update its server: address to that of the nlb_ip_address. Example:

scp [email protected]:/etc/rancher/k3s/k3s.yaml /tmp/
sed -i '/server:/ s/127.0.0.1/123.123.123.123/' /tmp/k3s.yaml

You can test it right away by running:

export KUBECONFIG=/tmp/k3s.yaml
kubectl get nodes

If that worked, then you can generate a new ~/.kube/config file with this trick:

export KUBECONFIG=/tmp/k3s.yaml:~/.kube/config
kubectl config view --flatten

If the output looks good, pipe it to ~/.kube/config