chore(kb/k8s/karpenter): mostly just add sources

knowledge base/kubernetes/karpenter.md

@@ -4,25 +4,29 @@ Open-source, just-in-time cloud node provisioner for Kubernetes.
 
 1. [TL;DR](#tldr)
 1. [Setup](#setup)
+   1. [AWS](#aws)
 1. [Further readings](#further-readings)
    1. [Sources](#sources)
 
 ## TL;DR
 
-Karpenter works by:
+Runs as workload on the cluster.
+
+Works by:
 
 1. Watching for unschedulable pods.
 1. Evaluating unschedulable pods' scheduling constraints (resource requests, node selectors, affinities, tolerations,
    and topology spread constraints).
-1. Provisioning **cloud-based** nodes meeting the requirements of unschedulable pods.
+1. Provisioning **cloud-based** nodes meeting the resource requirements and scheduling constraints of unschedulable
+   pods.
 1. Deleting nodes when no longer needed.
 
-Karpenter runs as workload on the cluster.
+Under the hood, Karpenter adds a finalizer to the Kubernetes node object it provisions.<br/>
+The finalizer blocks node deletion until all pods on it are drained and the instance is terminated.<br/>
+This **only** works for nodes provisioned by Karpenter.
 
-Should one manually delete a Karpenter-provisioned node, Karpenter will gracefully cordon, drain, and shutdown the
-corresponding instance.<br/>
-Under the hood, Karpenter adds a finalizer to the node object it provisions. This blocks deletion until all pods are
-drained and the instance is terminated. This **only** works for nodes provisioned by Karpenter.
+Should one manually delete a Karpenter-provisioned Kubernetes node object, Karpenter will gracefully cordon, drain, and
+shutdown the corresponding cloud instance.
 
 <details>
   <summary>Setup</summary>
@@ -71,10 +75,33 @@ helm … \
 
 Karpenter's controller and webhook deployment are designed to run as a workload on the cluster.
 
-As of 2024-12-24, it only supports AWS and Azure nodes.<br/>
+As of 2025-06-08, it only supports AWS and Azure nodes.<br/>
 As part of the installation process, one **will** need credentials from the underlying cloud provider to allow
 Karpenter-managed nodes to be started up and added to the cluster as needed.
 
+Karpenter configuration comes in the form of:
+
+- A _NodePool_ Custom Resource Definition.
+- A _NodeClass_ Custom Resource Definition.<br/>
+  Its specifics are defined by the cloud provider's implementation.
+
+A single Karpenter NodePool is capable of handling many different pod shapes.<br/>
+A cluster may have more than one NodePool.
+
+### AWS
+
+Leverages the [Karpenter provider for AWS].
+
+Requirements:
+
+- An IAM Role for Karpenter.<br/>
+  Required to allow Karpenter to call AWS APIs.
+- An IAM Role and an instance profile for the EC2 instances Karpenter creates.
+- An EKS cluster access entry for the nodes' IAM role.<br/>
+  Required by the nodes to be able to join the EKS cluster.
+- An SQS queue for Karpenter.<br/>
+  Required to receive Spot interruption, instance re-balance and other events.
+
 ## Further readings
 
 - [Website]
@@ -83,6 +110,11 @@ Karpenter-managed nodes to be started up and added to the cluster as needed.
 
 ### Sources
 
+- [Karpenter EKS workshop]
+- [Karpenter: Amazon EKS Best Practice and Cloud Cost Optimization]
+- [Run Kubernetes Clusters for Less with Amazon EC2 Spot and Karpenter]
+- [Karpenter best practices]
+
 <!--
   Reference
   ═╬═Time══
@@ -97,3 +129,8 @@ Karpenter-managed nodes to be started up and added to the cluster as needed.
 [website]: https://karpenter.sh/
 
 <!-- Others -->
+[Karpenter best practices]: https://docs.aws.amazon.com/eks/latest/best-practices/karpenter.html
+[Karpenter EKS workshop]: https://www.eksworkshop.com/docs/autoscaling/compute/karpenter/
+[Karpenter provider for AWS]: https://github.com/aws/karpenter-provider-aws
+[Karpenter: Amazon EKS Best Practice and Cloud Cost Optimization]: https://catalog.us-east-1.prod.workshops.aws/workshops/f6b4587e-b8a5-4a43-be87-26bd85a70aba/en-US
+[Run Kubernetes Clusters for Less with Amazon EC2 Spot and Karpenter]: https://community.aws/content/2dhlDEUfwElQ9mhtOP6D8YJbULA/run-kubernetes-clusters-for-less-with-amazon-ec2-spot-and-karpenter