Cluster API vs Karmada

Cluster API is an open-source project for managing the lifecycle of multiple Kubernetes clusters through declarative APIs and tooling. Platform operators can use it to create, scale, upgrade, and destroy Kubernetes-conformant clusters across on-premises and cloud environments. Provider implementations are interchangeable; kubeadm is the default bootstrap provider. The ecosystem includes infrastructure, bootstrap, control plane, IPAM, addon, and runtime extensions, with environments such as AWS, Azure, GCP, OpenStack, vSphere, and KubeVirt. A management cluster can use clusterctl or the Cluster API Operator to manage provider components. Clusterctl fetches provider component YAML and installs it, while the Operator uses a declarative approach intended to support GitOps workflows. Getting started requires an existing Kubernetes cluster accessible through kubectl; kind, Docker, and Helm are common prerequisites. Cluster API supports multi-cluster provisioning and upgrades, but does not manage a single cluster spanning multiple infrastructure providers or clusters it did not provision. It is free and open source. The project supports its latest two minor releases, with each supported for roughly 12 months including maintenance.

Karmada manages cloud-native applications across multiple Kubernetes clusters and clouds without requiring changes to the applications. It supports public and private cloud, on-premises, edge, and self-built environments that meet Kubernetes specifications. Cluster connections can use Push mode through a Kubernetes API server or Pull mode through an in-cluster agent. Scheduling policies cover cluster affinity, taints and tolerations, topology spread, and replicated or divided placement. OverridePolicy allows per-cluster changes to images, arguments, commands, and plain-text configuration. Karmada can move replicas after a cluster failure, including migration that avoids service replicas dropping to zero. Through karmada-apiserver, teams can create, update, delete, and query resources across member clusters. Its components export Prometheus metrics; integrations described include Submariner networking and ErieCanal service governance. Installation options include CLI tools, Helm, an operator, binaries, or source. The CLI initialization requires escalated privileges to store shared configuration under /etc/karmada by default. Karmada is open source and free, with customer-managed control plane; it manages clusters but does not provision them.