什么是 Kubernetes 及其核心概念是什么？

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Accepted Answer

**Kubernetes (K8s)** 是最主流的 **container orchestration** 平台——它自动化了在机器集群中部署、扩展和管理容器化应用程序的过程。理解其核心概念（pods、deployments、services 等）对于大规模运行容器至关重要。

## Kubernetes 的作用

```text
Kubernetes manages containers across a CLUSTER of nodes (machines), providing:
  → SCHEDULING (place containers on nodes), SELF-HEALING (restart failed containers),
    SCALING (up/down, auto), ROLLING UPDATES/rollbacks, SERVICE DISCOVERY,
    LOAD BALANCING, CONFIG/SECRET management, STORAGE orchestration
→ DECLARATIVE: you describe the DESIRED STATE; K8s continuously makes reality match it.
```

## 核心概念

```text
POD       → the smallest deployable unit: one (or a few tightly-coupled) containers
            sharing network/storage. K8s schedules pods (not bare containers).
DEPLOYMENT→ declares desired pods (replicas) for a stateless app; manages rollouts,
            scaling, self-healing (recreates pods to match the desired count).
SERVICE   → a stable network endpoint + load balancing for a set of pods (pods are
            ephemeral with changing IPs; a Service gives a stable name/IP).
INGRESS   → routes external HTTP(S) traffic to services (with rules, TLS).
CONFIGMAP / SECRET → inject configuration / sensitive data into pods.
NAMESPACE → virtual cluster partitioning (isolate environments/teams).
NODE      → a worker machine; the CONTROL PLANE manages the cluster.
```

## 声明式模型

```yaml
# describe DESIRED state in YAML; K8s makes it so (and keeps it so)
apiVersion: apps/v1
kind: Deployment
spec:
  replicas: 3                  # "I want 3 instances" → K8s ensures 3 are always running
  # if a pod dies, K8s creates a new one; if a node fails, pods move
```

## 为什么这很重要

理解 Kubernetes 及其核心概念对于 **大规模运行容器化应用程序** 是重要的高级知识，因为 Kubernetes 是主流的、行业标准的编排平台，是现代云原生部署的基础。

理解 **Kubernetes 的作用**——自动化调度、自我修复、扩展、滚动更新、服务发现以及跨集群的负载均衡，所有这些都通过 **声明式模型** 实现，在这种模型中你描述所需状态，Kubernetes 不断使现实与其一致——这捕捉了它提供的强大操作能力和基本方法。

理解 **核心概念** 对于使用 Kubernetes 至关重要：**pods**（最小的可部署单位，包装容器）、**deployments**（声明期望的副本数并为无状态应用管理部署、扩展和自我修复）、**services**（为短暂的 pods 提供稳定的网络端点和负载均衡——解决 pod IP 地址变化的问题）、**ingress**（路由外部流量）、**ConfigMaps/Secrets**（注入配置和敏感数据）以及 **namespaces**（分区集群）——这些是任何 Kubernetes 应用程序的构建块。

**声明式模型**（指定所需状态如