Kubernetes flashcards, generated for you.

A Service is an abstraction that exposes pods via a stable IP/DNS name. It's needed because pods are ephemeral; Services provide consistent networking and load balancing across pod replicas.

ClusterIP (internal only), NodePort (external via node port), LoadBalancer (cloud LB), and ExternalName (maps to external DNS).

`kubectl get svc` lists all services with cluster IPs and ports. Use `kubectl describe svc <name>` to see endpoints, selectors, and traffic routing details.

A Service uses a label selector to match pods. kube-proxy watches the Endpoints object and maintains iptables/IPVS rules to forward traffic from the service IP to matching pod IPs.

ClusterIP is only accessible within the cluster via stable IP. NodePort exposes the service on every node's IP at a port (30000-32767), allowing external access.

`kubectl create deployment <name> --image=<image>` creates the deployment, then `kubectl expose deployment <name> --port=<port> --type=NodePort` creates a Service.

A Headless Service has `clusterIP: None`. It returns individual pod IPs via DNS instead of a single service IP. Use for stateful applications (StatefulSets) where you need direct pod communication.

`kubectl port-forward` forwards local port traffic to a pod/service port, bypassing the service network. Example: `kubectl port-forward svc/<svc-name> 8080:80` forwards localhost:8080 to service port 80.

Ingress is an API object for HTTP/HTTPS routing, providing host/path-based rules and TLS termination. Services handle layer 4 (TCP/UDP); Ingress handles layer 7 (HTTP/HTTPS) and requires an Ingress Controller.

Check: (1) pod labels match service selector (`kubectl get pods --show-labels`), (2) endpoints are populated (`kubectl get endpoints`), (3) pod logs (`kubectl logs`), (4) DNS resolution (`kubectl run -it --rm debug --image=nicolaka/netshoot -- bash` then test with `nslookup`/`curl`).