Kubernetes

🧠 2025년 개정 CKA 시험 대비 핵심 가이드🔒 시험 운영 및 환경 변화기본 런타임 변경: containerd → dockerd 사용작업 환경: 모든 문제는 ssh로 접근하며, vim 설정 및 별칭(alias) 설정은 필요 없음시험 플랫폼: Killercoda(링크) 기반의 인터랙티브 쉘 환경이므로 익숙해질 것 📌 출제 및 평가 기준항목설명리소스 작성 방식kubectl의 명령형 imperative 방식을 우선적으로 사용할 것Manifest 사용 빈도직접 작성은 3회 이하, 그 외는 기존 리소스를 분석 및 수정하는 방식 위주평가 기준정답 도출뿐 아니라 얼마나 정확하고 명확하게 요구사항을 수행했는지가 평가 요소감점 요소불필요한 작업, 요구사항 미준수 시 감점될 수 있음시간 관리가장 중요한 요소. 시..

1. Rolling UpdatesDefinition: Gradually replaces old versions of Pods with new ones without downtime.How it worksKubernetes updates a few Pods at a time (controlled by maxUnavailable and maxSurge settings).New Pods are created first before old Pods are terminated.Deployment and StatefulSet controllers manage rolling updates.Key SettingsInside a Deployment YAML:strategy: type: RollingUpdate rol..

📌 1. Multiple Schedulers in KubernetesNormally, a Kubernetes cluster uses one scheduler: the default kube-scheduler. But Kubernetes allows multiple schedulers to coexist!Meaning, you can deploy and run custom schedulers alongside the default one. 🔹 How it works:A Pod can specify which scheduler it wants by setting the schedulerName field in its spec.Based on the schedulerName, Kubernetes dispa..

DaemonSet vs Static Pods in Kubernetes: A Technical Deep DiveWhen operating a Kubernetes environment, two critical concepts often surface: DaemonSets and Static Pods. Both ensure that specific workloads are deployed at the node level, but they operate on fundamentally different mechanisms. Understanding these differences is essential for designing a reliable and maintainable Kubernetes infrastru..

☣️ What is a Taint?A taint is applied to a node to mark it as unsuitable for certain pods, unless those pods explicitly tolerate the taint.It works like this:🛑 "This node doesn't want your pod... unless you're okay with my taint." 🔧 Taint Syntaxkubectl taint nodes key=value:effect 🧪 Examplekubectl taint nodes node1 key=env:NoSchedule🛡️ What is a Toleration?A toleration is added to a pod sp..

🧠 What is Scheduling in Kubernetes?Kubernetes scheduling is how the system decides which node should run a given Pod. The Kube-scheduler is the component that assigns Pods to Nodes.When you create a Pod, it starts in a "Pending" state. The scheduler looks at:The Pod’s requirements (like CPU, memory, labels)The cluster's current stateThe available nodesThen it picks the best node to run the Pod...

🌐 What is a Service in Kubernetes?A Service is an abstraction that defines a stable way to access a set of Pods (usually grouped by a label selector). It exposes an application running in your cluster behind a single outward-facing endpoint, even when the workload is split across multiple backends. Since Pods are ephemeral (they come and go), a Service ensures that your app always has a reliabl..

🔁 ReplicaSetA ReplicaSet (RS) ensures that a specified number of replica Pods are running at any given time. If a Pod goes down, the RS automatically creates a new one.🔧 Example YAML:apiVersion: apps/v1kind: ReplicaSetmetadata: name: my-replicasetspec: replicas: 3 selector: matchLabels: app: myapp template: metadata: labels: app: myapp spec: containers: ..

YAML (YAML Ain’t Markup Language) is a human-readable data serialization format, often used for configuration files, especially in tools like Kubernetes, Docker Compose, and Ansible.🧠 YAML ConceptsKey-Value PairsBasic structure is key: value.Indentation MattersYAML uses indentation (spaces only) to define structure. No tabs allowed.ListsRepresented with dashes -.Nested StructuresKeys can contai..

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. Here’s a breakdown of core concepts and main components:🔹 Core ConceptsClusterA set of machines (nodes) running Kubernetes. It consists of a control plane and worker nodes.NodeA physical or virtual machine in the cluster that runs pods. There are:Ma..