kubernetes编写yml简单入门

​ 编写kubernetes的yml资源清单有5个顶级的字段组成：apiVersion、kind、metadata、spec、status。

# 如果没有给定 group 名称，那么默认为 core，可以使用 kubectl apiversions # 获取当前 k8s 版本上所有的 apiVersion 版本信息( 每个版本可能不 同 )
apiVersion: group/apiversion
#资源类别
kind:
#资源元数据
metadata：
   name
   namespace
   lables
   annotations # 主要目的是方便用户阅读查找
# 期望的状态（disired state）
spec:
# 当前状态，本字段有 Kubernetes 自身维护，用户不能去定义
status：

​ 使用kubectl命令可以查看apiVersion的各个版本信息：

[[email protected] ~]# kubectl api-versions

​ 获取字段设置帮助文档

[[email protected] ~]# kubectl explain pod

​ 资源清单中大致可以分为如下几种类型：

apiVersion <string> #表示字符串类型 
metadata <Object> #表示需要嵌套多层字段 
labels <map[string]string> #表示由k:v组成的映射 
finalizers <[]string> #表示字串列表 
ownerReferences <[]Object> #表示对象列表 
hostPID <boolean> #布尔类型 
priority <integer> #整型 
name <string> -required- #如果类型后面接 -required-，表示为必填字段

1 创建nameSpace

​ 编写一个yml文件,文件的名称为dream21thnamespaces.yml，文件的内容如下：

apiVersion: v1
kind: Namespace
metadata:
  name: dream21th

​ 上传到服务器，执行下面指令，可以看到创建的名称为dream21th的namespace：

[[email protected] namespaces]# kubectl apply -f dream21thnamespaces.yml 
namespace/dream21th created
[[email protected] namespaces]# kubectl get ns
NAME              STATUS   AGE
default           Active   119d
dream21th         Active   7s
kube-node-lease   Active   119d
kube-public       Active   119d
kube-system       Active   119d

​ 执行下面指令删除dream21th的namespace：

[[email protected] namespaces]# kubectl delete -f dream21thnamespaces.yml 
namespace "dream21th" deleted

2 创建pod

​ 编写一个yml文件,文件的名称为dream21thtomcatpod.yml，文件的内容如下：

apiVersion: v1
kind: Pod
metadata:
  name: dream21th-tomcat-pod
  labels:
    app: dream21th-tomcat-pod
spec:
  containers:
    - name: dream21th-tomcat-pod
      image: tomcat:9.0.20-jre8-alpine
      imagePullPolicy: IfNotPresent
  restartPolicy: Always     

​ 上传到服务器，执行下面指令：

[[email protected] pod]# kubectl apply -f dream21thtomcatpod.yml 
pod/dream21th-tomcat-pod created
[[email protected] pod]# kubectl get pod
NAME                   READY   STATUS    RESTARTS   AGE
dream21th-tomcat-pod   1/1     Running   0          7s
[[email protected] pod]# kubectl get pod -o wide
NAME                   READY   STATUS    RESTARTS   AGE   IP           NODE        NOMINATED NODE   READINESS GATES
dream21th-tomcat-pod   1/1     Running   0          14s   10.244.1.8   k8s-work1   <none>           <none>
[[email protected] pod]# curl 10.244.1.8:8080

​ 镜像下载策略、重启策略：

imagePullPolicy: 
    Always:总是拉取  pull 
    IfNotPresent:如果本地有镜像，使用本地，如果本地没有镜像，下载镜像。 
    Never:只使用本地镜像，从不拉取

restartPolicy: 
    Always：只要退出就重启。 
    OnFailure：失败退出时（exit code不为0）才重启 
    Never：永远不重启

​ 删除上面部署的pod：

[[email protected] pod]# kubectl delete -f dream21thtomcatpod.yml 
pod "dream21th-tomcat-pod" deleted
[[email protected] pod]# kubectl get pod
No resources found in default namespace.

3 创建deployment

​ 编写一个yml文件,文件的名称为dream21thtomcatdeployment.yml，文件的内容如下：

apiVersion: apps/v1
kind: Deployment
metadata:
  name: dream21th-tomcat-deployment
  labels:
    app: dream21th-tomcat-deployment
spec:
  replicas: 3
  template:
    metadata:
      name: dream21th-tomcat-deployment
      labels:
        app: dream21th-tomcat
    spec:
      containers:
        - name: dream21th-tomcat-deployment
          image: tomcat:9.0.20-jre8-alpine
          imagePullPolicy: IfNotPresent
      restartPolicy: Always
  selector:
    matchLabels:
      app: dream21th-tomcat

​ 上传到服务器，执行下面指令：

[[email protected] deployment]# kubectl apply -f dream21thtomcatdeployment.yml 
deployment.apps/dream21th-tomcat-deployment created
[[email protected] deployment]# kubectl get pods
NAME                                           READY   STATUS    RESTARTS   AGE
dream21th-tomcat-deployment-5fc846c9bc-5rvkq   1/1     Running   0          10s
dream21th-tomcat-deployment-5fc846c9bc-j95mc   1/1     Running   0          10s
dream21th-tomcat-deployment-5fc846c9bc-ks88d   1/1     Running   0          10s
[[email protected] deployment]# kubectl get pods -o wide
NAME                                           READY   STATUS    RESTARTS   AGE   IP            NODE        NOMINATED NODE   READINESS GATES
dream21th-tomcat-deployment-5fc846c9bc-5rvkq   1/1     Running   0          18s   10.244.2.5    k8s-work2   <none>           <none>
dream21th-tomcat-deployment-5fc846c9bc-j95mc   1/1     Running   0          18s   10.244.1.10   k8s-work1   <none>           <none>
dream21th-tomcat-deployment-5fc846c9bc-ks88d   1/1     Running   0          18s   10.244.1.9    k8s-work1   <none>           <none>
[[email protected] deployment]# kubectl get deployment
NAME                          READY   UP-TO-DATE   AVAILABLE   AGE
dream21th-tomcat-deployment   3/3     3            3           28s
[[email protected] deployment]# kubectl get deployment -o wide
NAME                          READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS                    IMAGES                      SELECTOR
dream21th-tomcat-deployment   3/3     3            3           33s   dream21th-tomcat-deployment   tomcat:9.0.20-jre8-alpine   app=dream21th-tomcat

​ 注意：在Deployment中必须写matchLables；selector.matchLabels.app的值要和template.metadata.labels.app一致。

​ 可以通过下面的指令进行验证：

[[email protected] deployment]# curl 10.244.2.5:8080

​ 可以通过下面的指令删除上面部署的deployment：

[[email protected] deployment]# kubectl delete -f dream21thtomcatdeployment.yml 
deployment.apps "dream21th-tomcat-deployment" deleted
[[email protected] deployment]# kubectl get pods
No resources found in default namespace.

4 创建service

​ 编写一个yml文件,文件的名称为dream21thtomcatservice.yml，文件的内容如下：

apiVersion: apps/v1
kind: Deployment
metadata:
  name: dream21th-tomcat-deployment
  labels:
    app: dream21th-tomcat-deployment
spec:
  replicas: 3
  template:
    metadata:
      name: dream21th-tomcat-deployment
      labels:
        app: dream21th-tomcat
    spec:
      containers:
        - name: dream21th-tomcat-deployment
          image: tomcat:9.0.20-jre8-alpine
          imagePullPolicy: IfNotPresent
      restartPolicy: Always
  selector:
    matchLabels:
      app: dream21th-tomcat
---
apiVersion: v1
kind: Service
metadata:
  name: dream21th-tomcat-service
spec:
  selector:
    app: dream21th-tomcat
  ports:
    - port: 8888
      targetPort: 8080
      nodePort: 30089
      protocol: TCP
  type: NodePort

​ 执行下面指令，并验证：

[[email protected] service]# kubectl apply -f dream21thtomcatservice.yml 
deployment.apps/dream21th-tomcat-deployment created
service/dream21th-tomcat-service created
[[email protected] service]# kubectl get svc
NAME                       TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)          AGE
dream21th-tomcat-service   NodePort    10.96.13.168   <none>        8888:30089/TCP   7s
kubernetes                 ClusterIP   10.96.0.1      <none>        443/TCP          119d
[[email protected] service]# kubectl get deployment
NAME                          READY   UP-TO-DATE   AVAILABLE   AGE
dream21th-tomcat-deployment   3/3     3            3           18s
[[email protected] service]# kubectl get pod -o wide
NAME                                           READY   STATUS    RESTARTS   AGE   IP            NODE        NOMINATED NODE   READINESS GATES
dream21th-tomcat-deployment-5fc846c9bc-5jhd9   1/1     Running   0          24s   10.244.2.6    k8s-work2   <none>           <none>
dream21th-tomcat-deployment-5fc846c9bc-p26kj   1/1     Running   0          24s   10.244.1.12   k8s-work1   <none>           <none>
dream21th-tomcat-deployment-5fc846c9bc-xpnd5   1/1     Running   0          24s   10.244.1.11   k8s-work1   <none>           <none>
[[email protected] service]# curl 192.168.43.103:30089

​ Service参数和Service类型：

port ：访问service使用的端口 
targetPort ：Pod中容器端口 
NodePort： 通过Node实现外网用户访问k8s集群内service(30000-32767)

ClusterIP：默认，分配一个集群内部可以访问的虚拟IP 
NodePort：在每个Node上分配一个端口作为外部访问入口 
LoadBalancer：工作在特定的Cloud Provider上，例如Google Cloud，AWS，OpenStack 
ExternalName：表示把集群外部的服务引入到集群内部中来，即实现了集群内部pod和集群外部的服务 进行通信

​ 执行下面的指令删除上面部署的svc和deployment。

[[email protected] service]# kubectl delete -f dream21thtomcatservice.yml 
deployment.apps "dream21th-tomcat-deployment" deleted
service "dream21th-tomcat-service" deleted