kubernetes

CKAD 复习：排障、Helm、CRD 与镜像工具

把 CKAD 中排障、Helm、CRD、OCI/Docker 和常用输出命令压缩成速查模板

排障题不要凭感觉改，先按固定链路收证据：get 看状态，describe 看事件，logs 看应用，rollout 看发布，endpoints 看 Service 是否选中 Pod。

1. Deployment 启动失败

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k get deploy,pod -n troubleshooting -o wide
k describe deployment broken-deployment -n troubleshooting
k describe pod -l app=broken-app -n troubleshooting
k logs -l app=broken-app -n troubleshooting --all-containers=true
k get events -n troubleshooting --sort-by=.lastTimestamp

常见修法：

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# 镜像错
k set image deployment/broken-deployment nginx=nginx:1.19 -n troubleshooting

# 资源限制缺失或过低
k patch deployment broken-deployment -n troubleshooting --patch '{"spec":{"template":{"spec":{"containers":[{"name":"nginx","resources":{"requests":{"cpu":"100m","memory":"128Mi"},"limits":{"cpu":"200m","memory":"256Mi"}}}]}}}}'

# 观察发布结果
k rollout status deployment/broken-deployment -n troubleshooting
k rollout history deployment/broken-deployment -n troubleshooting

2. Service 不通

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k get svc web-service -n troubleshooting -o wide
k describe svc web-service -n troubleshooting
k get endpoints web-service -n troubleshooting
k get pod -n troubleshooting --show-labels
k run tmp --restart=Never --rm -i --image=busybox -- wget -O- web-service:80

判断：

  • endpoints 为空：selector 和 Pod label 不匹配。
  • endpoints 有 IP 但访问失败：检查 targetPort、容器监听端口、NetworkPolicy。
  • 只有某个 Pod 失败：看该 Pod 的 logs/events。

3. 常用输出与定位

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# 所有命名空间资源概览
k get pod -A -o wide
k get deploy,svc,ingress,netpol -A

# 自定义列
k get pod -A -o custom-columns='NS:.metadata.namespace,NAME:.metadata.name,NODE:.spec.nodeName,IMAGE:.spec.containers[*].image'

# JSONPath
k get pod nginx -o jsonpath='{.spec.containers[*].image}'

# 排序事件
k get events -A --sort-by=.lastTimestamp

4. Helm 基础题

Helm 题通常是添加仓库、安装 chart、升级、回滚、卸载。

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k create ns web
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

helm install nginx bitnami/nginx -n web --set replicaCount=2
helm list -n web
helm status nginx -n web

helm upgrade nginx bitnami/nginx -n web --set replicaCount=3
helm history nginx -n web
helm rollback nginx 1 -n web
helm uninstall nginx -n web

5. CRD 最小模板

CRD 题只要能写出 group、kind、plural、version、schema。

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apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: backups.data.example.com
spec:
  group: data.example.com
  scope: Namespaced
  names:
    plural: backups
    singular: backup
    kind: Backup
    shortNames:
    - bkp
  versions:
  - name: v1alpha1
    served: true
    storage: true
    schema:
      openAPIV3Schema:
        type: object
        properties:
          spec:
            type: object
            properties:
              source:
                type: string
              destination:
                type: string

6. OCI/Docker 基础

如果题目要求处理镜像归档或 Dockerfile，记住最短路径：

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cat > Dockerfile <<'EOF'
FROM nginx:alpine
COPY index.html /usr/share/nginx/html/
EXPOSE 80
EOF

docker build -t ckad-nginx:latest .
docker save ckad-nginx:latest -o /tmp/ckad-nginx.tar
docker load -i /tmp/ckad-nginx.tar

OCI 归档类题：

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docker pull nginx:latest
docker save nginx:latest -o /tmp/nginx-image.tar
mkdir -p /root/oci-images
tar -xf /tmp/nginx-image.tar -C /root/oci-images

考场压缩记忆

  • 排障先证据后修改：get -> describe -> logs -> events。
  • Deployment 修复后必须 rollout status。
  • Service 题核心看 endpoints。
  • Helm 固定顺序：repo add/update -> install -> list/status -> upgrade/rollback。
  • CRD 固定骨架：group + names + versions + schema。
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