What Is Kubernetes?#

Kubernetes, also known as K8s, is an open-source system for automating deployment, scaling, and management of containerized applications.
– The Kubernetes team

Kubernetes orchestrates and manages collections of containers (often using container runtimes like containerd). It takes care of scaling, distribution, and connectivity among these containers. Think of it as a system to manage many containers and the infrastructure they run on.

For example, you could install Docker on a single server, and route traffic directly to it. That’s fairly simple to set up, but what if you want 10 instances of that server? What about 1000 instances? What if you want to deploy many different services, each scaling up with more instances depending on load? Those are the problems that Kubernetes solves.

Kubernetes is the container orchestration platform. Nearly every modern DevOps workflow runs on top of it in production. I use Kubernetes to:

Orchestrate containers across single-node (Minikube) and multi-node aws(WORK IN PROGRESS) clusters
Declare the desired state with YAML manifests and let controllers reconcile it
Load balance and expose services through Services, Ingress and Gateways
Control who can do what with RBAC
Scale workloads vertically and horizontally (HPA)
Persist state with volumes, PVCs and persistent storage
Run stateful workloads like databases with StatefulSets
Run batch work and scheduled tasks with Jobs and CronJobs
And much more

Kubernetes konular (Konuları sırayla takip ederseniz, verdiğim görevlerin birbiriyle bağlantılı olduğunu ve sistemin pratikte nasıl çalıştığını daha net görebilirsiniz.)#

Temeller#

kubernetes-minikube = Minikube ile local cluster, kubectl create deployment, port-forward, Prod vs Minikube farkı
kubernetes-pods-minikube = Pod kavramı, ephemeral doğası, kubectl logs/delete pod, pod’ların unique IP adresleri
kubernetes-deployments-minikube = Deployment ve ReplicaSet, desired vs current state, kubectl get/edit deployment
kubernetes-probes = Liveness/Readiness/Startup probes, httpGet/tcpSocket/exec, rolling update’lerde probes’un rolü
kubernetes-deployment-rollouts = Rolling update (maxSurge/maxUnavailable), kubectl set image, rollout status/history/undo, bozuk imajdan kurtarma
kubernetes-yaml-configurations = YAML manifest yapısı (apiVersion, kind, spec), ConfigMap, env/envFrom, Secrets

Secret’lar, RBAC ve Batch İşleri#

kubernetes-secrets = kubectl create secret, secretKeyRef/envFrom/volume mount, base64 ≠ şifreleme, Sealed Secrets/External Secrets
kubernetes-rbac = ServiceAccount (token mount), Role/ClusterRole, RoleBinding/ClusterRoleBinding, kubectl auth can-i --as
kubernetes-jobs-cronjobs = Job (completions/parallelism/backoffLimit), CronJob (schedule/concurrencyPolicy), db.json yedekleme pipeline’ı

Ağ (Services, Ingress, Gateway & TLS)#

kubernetes-services = ClusterIP, NodePort, LoadBalancer, ExternalName, stable endpoint ve load balancing
kubernetes-ingress = Ingress controller (nginx) vs Ingress resource, host/path kuralları, ingressClassName, TLS + Secret
kubernetes-gateway-minikube = Gateway API (Envoy), HTTPRoute, /etc/hosts + minikube tunnel, annotations
kubernetes-namespaces = kubectl create ns, -n flag, intra-cluster DNS (svc.cluster.local)
kubernetes-dns-coredns = CoreDNS + Corefile ConfigMap, dnsPolicy/ndots, nslookup ile DNS troubleshooting, kube-dns servisi

Ölçeklendirme#

kubernetes-scaling-vertical = metrics-server, kubectl top (pod + node), resource limits (50m CPU, 256Mi RAM), CrashLoopBackOff
kubernetes-scaling-horizontal = HorizontalPodAutoscaler (HPA), minReplicas/maxReplicas, CPU hedefli otomatik ölçekleme

Depolama#

kubernetes-storage = Ephemeral filesystem, emptyDir volumes, multi-container pod’lar (sidecar), veritabanları
kubernetes-persistent-volumes = PersistentVolume (PV), PersistentVolumeClaim (PVC), dynamic provisioning, volumeMounts
kubernetes-storage-classes = StorageClass (provisioner/volumeBindingMode/allowVolumeExpansion), access modes (RWO/ROX/RWX), reclaimPolicy Retain/Delete, static PV
kubernetes-statefulsets = Stable identity, volumeClaimTemplates ile pod başına PVC, headless services, PostgreSQL örneği

Prod’e Geçiş#

kubernetes-nodes-basic = Control plane ve worker node’lar, GKE/EKS/AKS, resource requests vs limits