k8s (2)k8s资源清单的编写

ゝ一世哀愁。 2022-12-28 01:41 197阅读 0赞

### 文章目录 ###

*   *   *  什么是资源？
         *  什么是资源清单？
         *  资源清单的格式
         *   *  通过清单部署nginx

### 什么是资源？ ###

k8s中所有的内容都抽象为资源，资源实例化之后，叫做对象。

### 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

### 资源清单的格式 ###

[k8s@server1 ~]$ 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/sig-architecture/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/sig-architecture/api-conventions.md#types-kinds
    
       metadata     <Object>
         Standard object's metadata. More info:
         https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
    
       spec <Object>
         Specification of the desired behavior of the pod. More info:
         https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
    
       status       <Object>
         Most recently observed status of the pod. This data may not be up to date.
         Populated by the system. Read-only. More info:
         https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status

一个pod必须要有apiVersion，kind，metadata，spec  
apiVersion:k8s api的版本，指明api资源属于那个群组和版本，同一个组可以有多个版本，目前基本是V1，可以使用kubectl api-versions命令查询

[k8s@server1 ~]$ kubectl api-versions 
    admissionregistration.k8s.io/v1
    admissionregistration.k8s.io/v1beta1
    apiextensions.k8s.io/v1
    apiextensions.k8s.io/v1beta1
    apiregistration.k8s.io/v1
    apiregistration.k8s.io/v1beta1
    apps/v1
    authentication.k8s.io/v1
    authentication.k8s.io/v1beta1
    authorization.k8s.io/v1
    authorization.k8s.io/v1beta1
    autoscaling/v1
    autoscaling/v2beta1
    autoscaling/v2beta2
    batch/v1
    batch/v1beta1
    certificates.k8s.io/v1
    certificates.k8s.io/v1beta1
    coordination.k8s.io/v1
    coordination.k8s.io/v1beta1
    discovery.k8s.io/v1beta1
    events.k8s.io/v1
    events.k8s.io/v1beta1
    extensions/v1beta1
    flowcontrol.apiserver.k8s.io/v1beta1
    networking.k8s.io/v1
    networking.k8s.io/v1beta1
    node.k8s.io/v1
    node.k8s.io/v1beta1
    policy/v1beta1
    rbac.authorization.k8s.io/v1
    rbac.authorization.k8s.io/v1beta1
    scheduling.k8s.io/v1
    scheduling.k8s.io/v1beta1
    storage.k8s.io/v1
    storage.k8s.io/v1beta1
    v1

前面是组，后面是版本  
kind(String):yaml文件定义的资源类型和角色，比如Pod  
metadata(Object):元数据对象，固定值就写metadata  
metadata.name(String):元数据对象的名字，由我们编写，如定义Pod的名字  
metadata.namespace:元数据对象的命名空间，由我们自身定义  
Spec(Object):详细定义对象，固定值就写Spec  
spec.containers:Spec对象的容器列表定义，是个列表  
spec.containers\[\].name(String):定义容器的名字  
spec.containers\[\].image(String):容器用到的镜像名称  
上面的属性可以通过kubectl explain 查看

#### 通过清单部署nginx ####

apiVersion: v1
    kind: Pod
    metadata:
      name: pod1
    spec:
      containers:
      - name: nginx
        image: nginx:1.18.0
        imagePullPolicy: IfNotPresent

*  创建与删除

[k8s@server1 ~]$ kubectl apply -f pod.yml 
    pod/pod1 created
    [k8s@server1 ~]$ kubectl get pod --all-namespaces
    NAMESPACE     NAME                              READY   STATUS    RESTARTS   AGE
    default       pod1                              1/1     Running   0          9s
    [k8s@server1 ~]$ kubectl delete -f pod.yml 
    pod "pod1" deleted
    [k8s@server1 ~]$ kubectl get pod 
    No resources found in default namespace.

*  升级

[k8s@server1 ~]$ cat pod.yml 
    apiVersion: v1
    kind: Pod
    metadata:
      name: pod1
    spec:
      containers:
      - name: nginx
        image: nginx:latest 
        imagePullPolicy: IfNotPresent
    [k8s@server1 ~]$ kubectl apply -f pod.yml 
    pod/pod1 created
    [k8s@server1 ~]$ kubectl describe pod1
    Events:
      Type    Reason     Age   From               Message
      ----    ------     ----  ----               -------
      Normal  Scheduled  18s   default-scheduler  Successfully assigned default/pod1 to server3
      Normal  Pulled     16s   kubelet            Container image "nginx:latest" already present on machine
      Normal  Created    15s   kubelet            Created container nginx
      Normal  Started    14s   kubelet            Started container nginx

*  添加资源限制  
    因为用的是自主式单一pod，不允许直接更新，需要先删除pod

apiVersion: v1
    kind: Pod
    metadata:
      name: pod1
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        imagePullPolicy: IfNotPresent
        resources: 
          requests:
            cpu: "0.5"
            memory: "25M"
          limits:
            cpu: "1"
            memory: "50M"

[k8s@server1 ~]$ kubectl describe pod pod1
       Limits:
          cpu:     1
          memory:  50M
        Requests:
          cpu:        500m
          memory:     25M

*  设置网络

[root@server2 ~]# netstat -antlup | grep :80
    tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      4072/nginx: master  
    tcp6       0      0 :::80                   :::*                    LISTEN      4072/nginx: master

*  pod 特性 ：在一个pod内部 容器间可以相互通信，并且使用一个存储

[k8s@server1 ~]$ kubectl apply -f pod.yml 
    pod/pod1 created
    [k8s@server1 ~]$ kubectl get pod
    NAME   READY   STATUS      RESTARTS   AGE
    demo   0/1     Completed   0          49m
    pod1   2/2     Running     0          19s
    [k8s@server1 ~]$ kubectl attach pod1 -c busyboxplus -it
    If you don't see a command prompt, try pressing enter.
    / # curl localhost
    <!DOCTYPE html>
    <html>
    <head>
    <title>Welcome to nginx!</title>
    <style>
        body {
            width: 35em;
            margin: 0 auto;
            font-family: Tahoma, Verdana, Arial, sans-serif;
        }
    </style>
    </head>
    <body>
    <h1>Welcome to nginx!</h1>
    <p>If you see this page, the nginx web server is successfully installed and
    working. Further configuration is required.</p>
    
    <p>For online documentation and support please refer to
    <a href="http://nginx.org/">nginx.org</a>.<br/>
    Commercial support is available at
    <a href="http://nginx.com/">nginx.com</a>.</p>
    
    <p><em>Thank you for using nginx.</em></p>
    </body>
    </html>
    / # Session ended, resume using 'kubectl attach pod1 -c busyboxplus -i -t' command when the pod is running