k8s学习笔记之四:资源清单定义入门

第一章、k8s中的资源

1.什么叫资源？

k8s中所有的内容都抽象为资源， 资源实例化之后，叫做对象

2.在k8s中有哪些资源？

工作负载型资源(workload)： Pod ReplicaSet Deployment StatefulSet DaemonSet Job CronJob (ReplicationController在v1.11版本被废弃)
服务发现及负载均衡型资源(ServiceDiscovery LoadBalance):  Service  Ingress, ...
配置与存储型资源： Volume(存储卷) CSI(容器存储接口,可以扩展各种各样的第三方存储卷)
特殊类型的存储卷：ConfigMap(当配置中心来使用的资源类型)Secret(保存敏感数据) DownwardAPI(把外部环境中的信息输出给容器)
以上这些资源都是配置在名称空间级别 
集群级资源：Namespace Node Role ClusterRole RoleBinding(角色绑定) ClusterRoleBinding(集群角色绑定)
元数据型资源：HPA(Pod水平扩展) PodTemplate(Pod模板,用于让控制器创建Pod时使用的模板) LimitRange(用来定义硬件资源限制的)

第二章、资源清单

1.什么是资源清单

在k8s中，一般使用yaml格式的文件来创建符合我们预期期望的pod，这样的yaml文件我们一般称为资源清单

2.资源清单的格式

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

#配置清单主要有五个一级字段，其中status用户不能定义，有k8s自身维护

3.获取资源的apiVersion版本及资源配置的帮助

1)获取apiVersion版本信息

[root@k8s-master01 ~]# kubectl api-versions
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1
apiregistration.k8s.io/v1beta1
apps/v1
apps/v1beta1
apps/v1beta2
authentication.k8s.io/v1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1
authorization.k8s.io/v1beta1
autoscaling/v1
autoscaling/v2beta1
batch/v1
......(以下省略)

2)获取资源的apiVersion版本信息

[root@k8s-master01 ~]# kubectl explain pod
KIND:     Pod
VERSION:  v1
.....(以下省略)
[root@k8s-master01 ~]# kubectl explain Ingress
KIND:     Ingress
VERSION:  extensions/v1beta1

#可以看到出来，不同的资源可能属于不同的apiVersion版本

3)获取资源配置清单中字段设置帮助文档(以pod为例)

获取pod资源的配置清单一级字段

[root@k8s-master01 ~]# kubectl explain pod
KIND:     Pod
VERSION:  v1

DESCRIPTION:
     Pod is a collection of containers that can run on a host. This resource is
     created by clients and scheduled onto hosts.

FIELDS:
   apiVersion    <string>
     APIVersion defines the versioned schema of this representation of an
     object. Servers should convert recognized schemas to the latest internal
     value, and may reject unrecognized values. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#resources

   kind    <string>
     Kind is a string value representing the REST resource this object
     represents. Servers may infer this from the endpoint the client submits
     requests to. Cannot be updated. In CamelCase. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds
     ........
     ........

获取pod资源的配置清单二级级其他级别的字段

[root@k8s-master01 ~]# kubectl explain pod.metadata #查看一级字段中有哪些二级字段，字段的上下级以 "." 定义
KIND:     Pod
VERSION:  v1

RESOURCE: metadata <Object>

DESCRIPTION:
     Standard object's metadata. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata

     ObjectMeta is metadata that all persisted resources must have, which
     includes all objects users must create.
........

-------------

[root@k8s-master01 ~]# kubectl explain pod.metadata.labels #查看二级字段中有哪些三级字段
KIND:     Pod
VERSION:  v1

FIELD:    labels <map[string]string>

DESCRIPTION:
     Map of string keys and values that can be used to organize and categorize
     (scope and select) objects. May match selectors of replication controllers
     and services. More info: http://kubernetes.io/docs/user-guide/labels

字段配置的格式

帮助信息中常见格式如下：
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

第四章、创建一个配置清单实例

1.以pod为例，创建一个简单的yaml文件

[root@k8s-master01 ~]# mkdir manifests
[root@k8s-master01 ~]# cd manifests/
[root@k8s-master01 manifests]# cat pod-demo.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  labels:
    app: myapp        #给自己打上标签
    tier: frontend
spec:
  containers:         #创建了两个容器
  - name: nginx
    image: ikubernetes/myapp:v1
  - name: tomcat
    image: tomcat:-alpine
[root@k8s-master01 manifests]# kubectl create -f pod-demo.yaml #使用create 子命令以yaml文件的方式启动pod
[root@k8s-master01 manifests]# kubectl get pod   #主要查看pod的状态是否支持，因为有一个以上的pod，READY段需要注意pod中的容器是否全部就绪
NAME                            READY     STATUS      RESTARTS   AGE
......
pod-demo                        /       Running               2h

为了便于访问，我们再创建一个service便于外部访问测试

[root@k8s-master01 manifests]# cat svc-demo.yaml
apiVersion: v1
kind: Service      #主要类型
metadata:
  name: test-service
  labels:
    app1: nginx
    app2: tomcat
spec:
  ports:   #暴露的端口设置
  - name: nginx
    port: 80     #service的端口
    targetPort: 80    #pod上暴露的端口
    nodePort: 32080   #Node上暴露的端口，需要注意的是，Node只能暴露30000-32767之间的端口
  - name: tomcat
    port:
    targetPort:
    nodePort:
  selector:
    app: myapp
  type: NodePort    #service 端口暴露的类型，默认是ClusterIP
[root@k8s-master01 manifests]# kubectl create -f svc-demo.yaml

[root@k8s-master01 manifests]# kubectl get svc -o wide #查看svc的状态
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
.......
test-service  NodePort  10.108.230.27  <none>  80:32080/TCP,8080:32088/TCP  22m  app=myapp   #根据暴露的端口，加上任意集群的IP地址进行访问

2.pod资源清单示例

[root@k8s-master01 ~]# kubectl get pod     #查看集群中pod的状态，选取一个之前使用命令行状态下创建的pod
NAME                            READY     STATUS      RESTARTS   AGE
client                          /       Completed             19h
myapp-6d6f569fd5-rtgt9          /       Running               19h
myapp-6d6f569fd5-tjpfn          /       Running               19h
myapp-6d6f569fd5-tqq5z          /       Running               19h
nginx                           /       Running               16h
nginx-deploy-7db697dfbd-2qh7v   /       Running               20h
nginx-deploy-7db697dfbd-gskcv   /       Running               20h
nginx-deploy-7db697dfbd-ssws8   /       Running               20h
[root@k8s-master01 ~]# kubectl get pod nginx-deploy-7db697dfbd-2qh7v -o yaml  #使用 -o 参数 加yaml，可以将资源的配置以 yaml的格式输出出来，也可以使用json，输出为json格式
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: --30T05::55Z
  generateName: nginx-deploy-7db697dfbd-
  labels:
    pod-template-hash: ""
    run: nginx-deploy
  name: nginx-deploy-7db697dfbd-2qh7v
  namespace: default
  ownerReferences:
  - apiVersion: extensions/v1beta1
    blockOwnerDeletion: true
    controller: true
    kind: ReplicaSet
    name: nginx-deploy-7db697dfbd
    uid: 0eef9e1c-dbf0-11e8--5254001b07db
  resourceVersion: ""
  selfLink: /api/v1/namespaces/default/pods/nginx-deploy-7db697dfbd-2qh7v
  uid: 5ee94f2a-dc06-11e8--5254001b07db
spec:
  containers:
  - image: nginx:1.14-alpine
    imagePullPolicy: IfNotPresent
    name: nginx-deploy
    ports:
    - containerPort:
      protocol: TCP
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-tcwjz
      readOnly: true
  dnsPolicy: ClusterFirst
  nodeName: k8s-node02
  restartPolicy: Always
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds:
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds:
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds:
  volumes:
  - name: default-token-tcwjz
    secret:
      defaultMode:
      secretName: default-token-tcwjz
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: --30T05::55Z
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: --30T05::06Z
    status: "True"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: --30T05::55Z
    status: "True"
    type: PodScheduled
  containerStatuses:
  - containerID: docker://b75740e5919bd975755b256c83e03b63ea95cf2307ffc606abd03b59fea6634a
    image: docker.io/nginx:1.14-alpine
    imageID: docker-pullable://docker.io/nginx@sha256:8976218be775f4244df2a60a169d44606b6978bac4375192074cefc0c7824ddf
    lastState: {}
    name: nginx-deploy
    ready: true
    restartCount:
    state:
      running:
        startedAt: --30T05::06Z
  hostIP: 172.16.150.214
  phase: Running
  podIP: 10.244.2.7
  qosClass: BestEffort
  startTime: --30T05::55Z