Kubernetes simple introduction to writing YML

​ To write kubernetes Of yml Resource list has 5 Top level fields ：apiVersion、kind、metadata、spec、status.

#  If there is no given  group  name , Then the default is  core, have access to  kubectl apiversions #  Get current  k8s  All on the version  apiVersion  Version information (  Each version may not   Same as  )
apiVersion: group/apiversion
# Resource categories 
kind:
# Resource metadata 
metadata：
   name
   namespace
   lables
   annotations #  The main purpose is to facilitate users to read and find 
#  Desired state （disired state）
spec:
#  current state , This field has  Kubernetes  Self maintenance , Users cannot define 
status：

​ Use kubectl Commands can be viewed apiVersion Version information of ：

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

​ Get the field setting help document

[[email protected] ~]# kubectl explain pod

​ The resource list can be roughly divided into the following types ：

apiVersion <string> # Represents string type  
metadata <Object> # Indicates that you need to nest multiple fields  
labels <map[string]string> # By k:v The mapping of components  
finalizers <[]string> # Represents a list of strings  
ownerReferences <[]Object> # Represents a list of objects  
hostPID <boolean> # Boolean type  
priority <integer> # integer  
name <string> -required- # If the type is followed by  -required-, Indicates a required field 

1 establish nameSpace

​ Write a yml file , The name of the document is dream21thnamespaces.yml, The contents of the document are as follows ：

apiVersion: v1
kind: Namespace
metadata:
  name: dream21th

​ Upload to server , Execute the following instructions , You can see that the created name is dream21th Of 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

​ Execute the following instructions to delete dream21th Of namespace：

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

2 establish pod

​ Write a yml file , The name of the document is dream21thtomcatpod.yml, The contents of the document are as follows ：

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     

​ Upload to server , Execute the following instructions ：

[[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

​ Image Download Strategy 、 Restart strategy ：

imagePullPolicy: 
    Always: Always pull   pull 
    IfNotPresent: If there is a mirror image locally , Use local , If there is no image locally , Download mirroring . 
    Never: Use only local images , Never pull 

restartPolicy: 
    Always： Just exit and restart . 
    OnFailure： When you fail to exit （exit code Not for 0） To restart  
    Never： Never restart 

​ Delete the deployed above 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 establish deployment

​ Write a yml file , The name of the document is dream21thtomcatdeployment.yml, The contents of the document are as follows ：

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

​ Upload to server , Execute the following instructions ：

[[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

​ Be careful ： stay Deployment You have to write matchLables;selector.matchLabels.app The value of and template.metadata.labels.app Agreement .

​ It can be verified by the following instructions ：

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

​ You can delete the deployed above through the following instructions 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 establish service

​ Write a yml file , The name of the document is dream21thtomcatservice.yml, The contents of the document are as follows ：

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

​ Execute the following instructions , And verify ：

[[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 Parameters and Service type ：

port ： visit service Port used  
targetPort ：Pod Container port in  
NodePort：  adopt Node Realize the access of external network users k8s Within cluster service(30000-32767)

ClusterIP： Default , Assign a virtual machine that can be accessed within the cluster IP 
NodePort： At every Node Assign a port on as an external access entry  
LoadBalancer： Work in a particular Cloud Provider On , for example Google Cloud,AWS,OpenStack 
ExternalName： It refers to the introduction of services outside the cluster into the cluster , That is to realize the cluster inside pod And services outside the cluster   communicate 

​ Execute the following instructions to delete the deployed svc and deployment.

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