Kubernetes入门与进阶02

Pod

资源规范

apiVersion: Group/VERSION

alpha内部测试版本; v1v2就是stable稳定版

root@k8s-master02:~# kubectl api-versions
admissionregistration.k8s.io/v1
apiextensions.k8s.io/v1
apiregistration.k8s.io/v1
apps/v1
authentication.k8s.io/v1
... 
省略
...

CORE GROUP 就是v1这种不带GROUP的APIVERSION。是早期设计的时候没考虑那么多，后来不便修改。

kind

有的带组了，没带组的就是核心组

NAME 和 SHORTNAMES

metadata

name: 唯一，同一类型(上面的kind)下唯一；对于namepace级别的资源，同一名称空间下，同一类型中，必须唯一。

namespace K8S的namespace和docker的namespace式不同的 K8S Namespace：管“资源归属” 前置式、管理层、逻辑隔离。 先把资源在 Kubernetes API 层面分门别类。 Docker/Linux Namespace：管“进程看到的世界”。 运行时、内核层、系统视图隔离。 真正让容器进程看到“自己的进程、网卡、文件系统、主机名”等。 labels 标签，k: v 键值对，支持被筛选 annotations 注解，k:v 键值对，不能被筛选。

spec

期望的状态，不同资源类型的spec各不相同 了解特定资源类型下有哪些字段可以用

kubectl explain Deployment
kubectl explain Deployment.spec
kubectl explain Deployment.spec.template
kubectl explain Deployment.spec.template.metadata

3种用户：

①应用访问用户②开发运维③底层访问比如node节点等

kubectl命令提供的三种对象管理机制

指令式命令 kubectl create这种就是。属于一次性的操作任务，不适合深度定制 指令式对象配置 指令式，就是具体的操作步骤创建、删除、查看、修改，不像声明式直接要结果，适合深度定制 声明式对象配置 apply关键词，具有幂等性操作的效果，希望应用--有则直接用，不一样就修正，没有就创建。

api server的RESTFUL API CRUD

CRUD

kubectl create kubectl get/describe kubectl edit/patch/replace/set kubectl delete

HTTP method

get post put delete options ...

部署一个应用

1、编排运行，2、service发现和LB

root@k8s-master02:~# kubectl create deployment demoapp --image=ikubernetes/demoapp:v1.0 --replicas=3 --port=80 --dry-run=client -o yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: demoapp
  name: demoapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: demoapp
  strategy: {}
  template:
    metadata:
      labels:
        app: demoapp
    spec:
      containers:
      - image: ikubernetes/demoapp:v1.0
        name: demoapp
        ports:
        - containerPort: 80
        resources: {}
status: {}

解释：

apiVersion: apps/v1                 # 使用的 API 版本；Deployment 属于 apps/v1
kind: Deployment                    # 资源类型：Deployment，表示“部署/控制一组 Pod”
metadata:                           # 元数据，描述这个资源本身
  labels:                           # 给 Deployment 自己打标签
    app: demoapp                    # 标签 key=app，value=demoapp
  name: demoapp                     # Deployment 的名字叫 demoapp

spec:                               # 期望状态，告诉 Kubernetes 你想要什么
  replicas: 3                       # 副本数：希望运行 3 个 Pod

  selector:                         # 选择器，用来找到它要管理哪些 Pod
    matchLabels:                    # 按标签匹配 Pod
      app: demoapp                  # 管理带有 app=demoapp 标签的 Pod

  strategy: {}                      # 更新策略；这里为空，实际默认是 RollingUpdate 滚动更新

  template:                         # Pod 模板，用来创建 Pod
    metadata:                       # Pod 的元数据
      labels:                       # 给 Pod 打标签
        app: demoapp                # Pod 标签 app=demoapp，必须和 selector 匹配

    spec:                           # Pod 的具体规格
      containers:                   # 容器列表，一个 Pod 里可以有多个容器
      - image: ikubernetes/demoapp:v1.0   # 容器镜像：从镜像仓库拉 ikubernetes/demoapp:v1.0
        name: demoapp               # 容器名字叫 demoapp
        ports:                      # 声明容器暴露的端口
        - containerPort: 80         # 容器内部监听/暴露 80 端口
        resources: {}               # 资源限制/请求为空；没有设置 CPU、内存 request/limit

status: {}                          # 当前状态；dry-run 生成的 YAML 里为空，真正创建后由 K8S 自动填充

重点看这几组关系：

selector.matchLabels.app = demoapp
template.metadata.labels.app = demoapp

这两个必须能匹配上，否则 Deployment 不知道自己该管理哪些 Pod。

还有：

replicas: 3

表示 Deployment 会通过 ReplicaSet 维持 3 个 Pod。

--dry-run=client -o yaml 的意思是：只在客户端生成 YAML，不真正创建资源。

常规操作

root@k8s-master02:~# kubectl create deployment demoapp --image=ikubernetes/demoapp:v1.0 --replicas=3 --port=80 --dry-run=client -o yaml > deploy-demoapp.yaml
root@k8s-master02:~# vim deploy-demoapp.yaml # 进去删除没必要的配置
root@k8s-master02:~# cat deploy-demoapp.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: demoapp
  name: demoapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: demoapp
  template:
    metadata:
      labels:
        app: demoapp
    spec:
      containers:
      - image: ikubernetes/demoapp:v1.0
        name: demoapp
        ports:
        - containerPort: 80
root@k8s-master02:~#
root@k8s-master02:~# kubectl create -f deploy-demoapp.yaml
deployment.apps/demoapp created

root@k8s-master02:~# kubectl get deployments demoapp
NAME      READY   UP-TO-DATE   AVAILABLE   AGE
demoapp   1/3     3            1           2m16s
root@k8s-master02:~#
root@k8s-master02:~# kubectl get deployments demoapp -o wide
NAME      READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS   IMAGES                     SELECTOR
demoapp   1/3     3            1           2m21s   demoapp      ikubernetes/demoapp:v1.0   app=demoapp
root@k8s-master02:~#
root@k8s-master02:~# kubectl get deployments demoapp -o yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "1"
  creationTimestamp: "2026-05-27T10:12:06Z"
  generation: 1
  labels:
    app: demoapp
  name: demoapp
  namespace: default
  resourceVersion: "2066246"
  uid: b411ce34-d934-4e55-a183-1f4b04f94a9a
spec:
  progressDeadlineSeconds: 600
  replicas: 3
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: demoapp
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: demoapp
    spec:
      containers:
      - image: ikubernetes/demoapp:v1.0
        imagePullPolicy: IfNotPresent
        name: demoapp
        ports:
        - containerPort: 80
          protocol: TCP
        resources: {}
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      terminationGracePeriodSeconds: 30
status:
  availableReplicas: 1
  conditions:
  - lastTransitionTime: "2026-05-27T10:12:06Z"
    lastUpdateTime: "2026-05-27T10:12:06Z"
    message: Deployment does not have minimum availability.
    reason: MinimumReplicasUnavailable
    status: "False"
    type: Available
  - lastTransitionTime: "2026-05-27T10:12:06Z"
    lastUpdateTime: "2026-05-27T10:14:06Z"
    message: ReplicaSet "demoapp-964658bb8" is progressing.
    reason: ReplicaSetUpdated
    status: "True"
    type: Progressing
  observedGeneration: 1
  readyReplicas: 1
  replicas: 3
  terminatingReplicas: 0
  unavailableReplicas: 2
  updatedReplicas: 3
root@k8s-master02:~#

其实资源有三份：

1、自己写的yaml：deploy-demoapp.yaml。

2、部署后生成的：kubectl get deployments demoapp -o yaml上的spec的期望值；保存在etcd里的配置。

3、部署后生成的：kubectl get deployments demoapp -o yaml上的status实际状态；部署后运行起来这是controller实现的，同时status字段也是controller回填的。

cli的写法

显示资源：
kukectl get TYPE [NAME ...] -o {wide|yaml|json}
kubectl get TYPE/NAME ... -O {wide|yaml|json}

删除资源
kubectl delete TYPE [NAME ...]
kubectl delete TYPE/NAME ...

详细的状态描述
kubectl describe TYPE [NAME ...]
kubectl describe TYPE/NAME ...

在pod的某容器内部执行命令
kubectl exec [-it] POD [-c CONTAINER] -- COMMAND [args...] [options]

查看容器日志
kubectl logs [-f] (POD | TYPE/NAME) [-c CONTAINER]

一条cli查看多个type资源

root@k8s-master02:~# kubectl get deploy/nginx svc/whoami

查看所有资源

root@k8s-master02:~# kubectl get all

查看命名空间里的pods

root@k8s-master02:~# kubectl get namespaces
root@k8s-master02:~# kubectl get pods -n calico-system

查看标签

root@k8s-master02:~# kubectl get pods -n kube-system  --show-labels

标签过滤

root@k8s-master02:~# kubectl get pods -n kube-system  -l component=kube-scheduler

创建service

root@k8s-master02:~# kubectl create service clusterip demoapp --tcp=80:80 --dry-run=client -o yaml > service-demoapp.yaml

root@k8s-master02:~# kubectl create -f service-demoapp.yaml
root@k8s-master02:~# kubectl delete -f service-demoapp.yaml

apply的幂等性

root@k8s-master02:~# kubectl create -f service-demoapp.yaml
service/demoapp created
root@k8s-master02:~#
root@k8s-master02:~# kubectl create -f service-demoapp.yaml
Error from server (AlreadyExists): error when creating "service-demoapp.yaml": services "demoapp" already exists
root@k8s-master02:~#
root@k8s-master02:~# kubectl delete -f service-demoapp.yaml
service "demoapp" deleted from default namespace
root@k8s-master02:~#
root@k8s-master02:~# kubectl apply -f service-demoapp.yaml
service/demoapp created
root@k8s-master02:~# kubectl apply -f service-demoapp.yaml
service/demoapp unchanged
root@k8s-master02:~#

get查看配置对应创建的资源

root@k8s-master02:~# kubectl get -f service-demoapp.yaml
NAME      TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
demoapp   ClusterIP   10.109.81.248   <none>        80/TCP    101s
root@k8s-master02:~#

get pods后查看详情events排错

root@k8s-master01:~# kubectl get pods
root@k8s-master01:~# kubectl describe pod demoapp-964658bb8-8wgz5

进入pod的某个容器内部查看信息并退出

root@k8s-master01:~# kubectl get pods
root@k8s-master01:~# kubectl exec demoapp-964658bb8-8wgz5 -- ifconfig

进入pod的某个容器里

root@k8s-master01:~# kubectl exec -it demoapp-964658bb8-8wgz5 -- /bin/sh

查看日志

root@k8s-master01:~# kubectl get pods
root@k8s-master01:~# kubectl logs backend-79f8849978-z2q4p
root@k8s-master01:~# kubectl logs -f backend-79f8849978-z2q4p