Kubernetes 101

-   kube-apiserver
-   kube-controller-manager
-   kube-scheduler
-   etcd

-   Container Runtime
-   kubelet
-   kube-proxy
-   pod

kubectl [get|delete|edit|apply] [pods|deployment|services] [podName|serviceName|deploymentName]

apiVersion:
kind:
    # 资源类别，标记创建什么类型的资源: Pod, Deployment, Job 等
metadata:
    # 元数据内部是嵌套的字段
    # 定义了资源对象的名称、命名空间（k8s级别的不是系统的）等、标签、注解、UID等
    annotations:
    name: myproj-mysql
    labels: # labels recommended by k8s
        app.kubernetes.io/name: mysql
        app.kubernetes.io/instance: mysql-abcxzy
        app.kubernetes.io/version: '5.7.21'
        app.kubernetes.io/component: database
        app.kubernetes.io/part-of: wordpress
        app.kubernetes.io/managed-by: helm
        app.kubernetes.io/created-by: controller-manager
data:
    # 针对数据资源，如 Secret, ConfigMap
spec:
    # 规范定义资源应该拥有什么样的特性，依靠控制器确保特性能够被满足，各种资源有自己的spec
    # 用户定义所期望了资源状态
    containers:
        - name:
          image:
          ports:
              - containerPort:
          env:
              - name:
                value:
status:
    # 显示资源的当前状态，k8s 就是确保当前状态向目标状态无限靠近从而满足用户期望
    # 它是只读的，代表了资源当前状态

kubectl get pods -l "app=firstapp" --show-labels
kubectl get pods -l "app=firstapp,tier=frontend" --show-labels
kubectl get pods -l "app=firstapp,tier!=frontend" --show-labels
kubectl get pods -l "app,tier=frontend" --show-labels #equality-based selector
kubectl get pods -l "app in (firstapp)" --show-labels  #set-based selector
kubectl get pods -l "app not in (firstapp)" --show-labels  #set-based selector
kubectl get pods -l "app=firstapp,app=secondapp" --show-labels # comma means and => firstapp and secondapp
kubectl get pods -l "app in (firstapp,secondapp)" --show-labels # it means or => firstapp or secondapp

kubectl apply -f podnode.yaml
kubectl get pods -w #always watch
kubectl label nodes minikube hddtype=ssd #after labelling node, pod11 configuration can run, because node is labelled with hddtype:ssd

apiVersion: v1
kind: ConfigMap
metadata:
    name: simple-web-config
    namespace: default
data:
    configuration_key: 'Configuration value'

apiVersion: v1
kind: Secret
metadata:
    name: simple-web-secrets
# Opaque can hold generic secrets, so no validation will be done.
type: Opaque
data:
    # Secrets should be encoded in base64
    secret_configuration_key: 'c2VjcmV0IHZhbHVl'

apiVersion: v1
kind: Pod
metadata:
    name: my-web-server
spec:
    # <containers> is a list of container definition to embed in the pod
    containers:
        - name: web
          image: nginx
          ports:
              - name: web
                containerPort: 80
                protocol: TCP
          env:
              - name: SOME_CONFIG
                # Create a line "value: <config_entry>" from the ConfigMap data
                valueFrom:
                    configMapKeyRef:
                        name: simple-web-config
                        key: configuration_key
              - name: SOME_SECRET
                # Create a line "value: <config_entry>" from the Secret data
                valueFrom:
                    secretKeyRef:
                        name: simple-web-secrets
                        key: secret_configuration_key

apiVersion: apps/v1
kind: ReplicaSet
metadata:
    name: myrs
    namespace: default
spec:
    replicas: 2
    selector:
        matchLabels:
            app: myapp
            release: canary
    template:
        metadata:
            name: myapp-pod
            labels:
                app: myapp # 标签一定要符合 replicaset 标签选择器的规则
                release: canary
        spec:
            containers:
                - name: myapp-containers
                  image: ikubernetes/myapp:v1
                  ports:
                      - name: http
                        containerPort: 80

apiVersion: apps/v1
kind: Deployment
metadata:
    name: my-web-server-deployment
    namespace: default
    labels:
        app: webserver
spec:
    # <selector> should retrieve the Pod defined below, and possibly more
    selector:
        matchLabels:
            app: webserver
            instance: nginx-ws-deployment
    # <replicas> asks for 3 pods running in parallel at all time
    replicas: 3
    # The content of <template> is a Pod definition file, without <apiVersion> nor <kind>
    template:
        metadata:
            name: my-web-server
            namespace: default
            labels:
                app: webserver
                instance: nginx-ws-deployment
        spec:
            containers:
                - name: web
                  image: nginx
                  ports:
                      - name: web
                        containerPort: 80
                        protocol: TCP
                  env:
                      - name: SOME_CONFIG
                        # Create a line "value: <config_entry>" from the ConfigMap data
                        valueFrom:
                            configMapKeyRef:
                                name: simple-web-config
                                key: configuration_key
                      - name: SOME_SECRET
                        # Create a line "value: <config_entry>" from the Secret data
                        valueFrom:
                            secretKeyRef:
                                name: simple-web-secrets
                                key: secret_configuration_key

apiVersion: v1
kind: Service
metadata:
    name: simple-web-service-clusterip
spec:
    # ClusterIP is the default service <type>
    type: ClusterIP
    # Select all pods declaring a <label> entry "app: webserver"
    selector:
        app: webserver
    ports:
        - name: http
          protocol: TCP
          # <port> is the port to bind on the service side
          port: 80
          # <targetPort> is the port to bind on the Pod side
          targetPort: 80

# <kind> is the type of resource to create (e.g. deployment, secret, namespace, quota, ...)
$ kubectl create <kind> <name>
$ kubectl edit   <kind> <name>
$ kubectl delete <kind> <name>

# All those commands can be used through a description file.
$ kubectl create -f <resource>.yaml
$ kubectl edit   -f <resource>.yaml
# create & update
$ kubectl apply  -f <resource>.yaml
$ kubectl delete -f <resource>.yaml

kubectl set image deployment rolldeployment nginx=httpd:alpine --record     # change image of deployment
kubectl rollout history deployment rolldeployment                           #shows record/history revisions
kubectl rollout history deployment rolldeployment --revision=2              #select the details of the one of the revisions
kubectl rollout undo deployment rolldeployment                              #returns back to previous deployment revision
kubectl rollout undo deployment rolldeployment --to-revision=1              #returns back to the selected revision=1
kubectl rollout status deployment rolldeployment -w                         #show live status of the rollout deployment
kubectl rollout pause deployment rolldeployment                             #pause the rollout while updating pods
kubectl rollout resume deployment rolldeployment                            #resume the rollout if rollout paused