Harden & Lockdown RKE2 Cluster with a 4-Layer DevSecOps Stack
Introduction Before you move furniture into a new house, you install the locks, the cameras, and the gates. Kubernetes is no different, yet engineers constantly build clusters inside-out, treating security as a cosmetic bolt-on to be handled "later." Not this time. The order here is entirely deliberate. You don't move into a finished house and then start wondering about the security system—you…
Before investing in a new home, homeowners install locks, cameras, and gates to secure the property. Similarly, in Kubernetes, security should be implemented from the outset rather than as an afterthought. In this case, a 29-node RKE2 cluster was set up across three Proxmox datacenters, but remained empty.
To ensure the cluster's security, four cloud-native security engines were integrated before any workloads were introduced. These engines include Kyverno for admission control, KubeArmor for runtime enforcement, Falco for behavioral detection, and Trivy for continuous vulnerability scanning.
The implementation of these security measures is documented in the kubernetes-addons/security-stack/ repository, which consists of README.md files, kustomization.yaml files, namespace.yaml files, policy configurations, and various charts. These components work independently, with each one providing a distinct layer of security.
By employing a GitOps workflow via ArgoCD, the security stack becomes a version-controlled commitment, with every policy configuration stored as a commit. The article outlines the specific methods employed to integrate these four security engines into a unified defensive front, covering the entire workload lifecycle, from admission control to continuous scanning.
The article emphasizes that this security layer is part of a larger infrastructure series that documents the evolution of the cluster. By securing the platform before any important workloads are deployed, the blast radius of potential compromises is minimized. The article also highlights the importance of this security approach for modern homelab environments, which often host sensitive components such as HashiCorp Vault, Keycloak, MLflow, Kubeflow, and Harbor.
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