About a pod
1.1 Introduction
- Pod is the basis K8s cluster all business types
- Pod is the smallest unit in K8s running in the cluster deploy applications or services, it can support multiple containers.
- Pod's design philosophy is to support multiple containers shared network addresses and file system in a Pod
Difference pod and containers is that a pod can have multiple containers, when a pod is only a container, access pod is access to the container, for a kubernets, one pods have at least two containers, one is invisible, vessel called the pause, the other is the container business
pod is a logical concept, a container pod anomalies, re-create the entire pod
- Pod Kubernetes each assigned a unique IP address, called PodIP, a plurality of containers in a Pod PodIP shared address. Requirements of the underlying network supports direct communication between any two cluster Pod, usually virtual network technology to implement Layer (Flannel).
- POD POD can communicate directly with the other hosts.
- If there POD stops unexpectedly, K8S will restart based on the resource settings or create POD, until the set value in line with expectations
- pause vessel hijacked container business all traffic, IP is configured in a pause of the container, when creating the pod automatically created to take over the container network
1.2 pod of a scenario
- pod containing two containers, File Puller first start in web server container
- Pulling code into the volume, and then self-destruct
- web server container starts, the volume readings code for user access
Two POD simple operation
2.1 Creating a pods of about nginx
[root@docker-server1 namespace]# cd ../
[root@docker-server1 yamls]# mkdir pods
[root@docker-server1 yamls]# cd pods
[root@docker-server1 pods]# vi nginx-pods.yaml
apiVersion: v1 kind: Pod metadata: name: nginx labels: app: nginx annotations: test: this is a test app spec: #资源描述信息 containers: - name: nginx image: nginx ports: - containerPort: 80
This is one of the most simple of pods, but nginx is running a business, there is no other thing
[root@docker-server1 pods]# kubectl apply -f nginx-pods.yaml
Since there is no designated ns, so the pods running in defaults, view
[root@docker-server1 pods]# kubectl get pods
NAME READY STATUS RESTARTS AGE nginx 1/1 Running 0 85s
1/1: 1 indicates that the back of the pods run several containers in front of the container 1 represents several state is redy
View container
[root@docker-server1 pods]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx 1/1 Running 0 6m41s 10.244.2.6 192.168.132.133 <none> <none>
access
[root@docker-server1 pods]# curl http://10.244.2.6
<!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>
2.2 Configuring port mapping
[root@docker-server1 pods]# vim nginx-pods.yaml
apiVersion: v1 kind: Pod metadata: name: nginx labels: app: nginx spec: hostNetwork: true containers: - name: nginx image: nginx ports: - containerPort: 80
[root@docker-server1 pods]# kubectl delete -f nginx-pods.yaml
[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml
[root@docker-server1 pods]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx 0/1 ContainerCreating 0 4s 192.168.132.133 192.168.132.133 <none> <none>
[root@docker-server1 pods]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx 1/1 Running 0 95s 192.168.132.133 192.168.132.133 <none> <none>
2.3 pod common configuration
name: String Image: String imagePullPolicy: [Always | Never | IfNotPresent] # pulling mirror policy, the default is the third, look at the local, local is not only pulling restartPolicy: [Always | Never | OnFailure] the Command: [ String ] args: [ String ] the ports: containerPort: int hostPort: int Protocol: String the env : name: String value: String hostNetwork: BOOL Resources Volumes livenessProbe ReadnessProbe
2.4 on other policy
Running a plurality of containers, and using pulling mirror policy
[root@docker-server1 pods]# vim nginx-pods.yaml
apiVersion: v1 kind: Pod metadata: name: nginx labels: app: nginx annotations: test: this is a test app spec: imagePullPolicy: Always restartPolicy: Always containers: - name: nginx image: nginx ports: - containerPort: 80 hostPost: 8080 env: - name: test value: aaa - name: test1 value: bbb - name: busybox image: busybox command: - sh - -c - sleep 3600
2.4 Delete and then create pod
[root@docker-server1 pods]# kubectl delete pod nginx
[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml
error: error validating "nginx-pods.yaml": error validating data: ValidationError(Pod.spec): unknown field "imagePullPolicy" in io.k8s.api.core.v1.PodSpec; if you choose to ignore these errors, turn validation off with --validate=false
imagePullPolicy this can not specify all containers
[root@docker-server1 pods]# vim nginx-pods.yaml
apiVersion: v1 kind: Pod metadata: name: nginx labels: app: nginx annotations: test: this is a test app spec: restartPolicy: Always containers: - name: nginx image: nginx imagePullPolicy: Always ports: - containerPort: 80 hostPort: 8080 env: - name: test value: aaa - name: test1 value: bbb - name: busybox image: busybox command: - sh - -c - sleep 3600
[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml
[root@docker-server1 pods]# kubectl get pods
NAME READY STATUS RESTARTS AGE nginx 2/2 Running 0 28s
[root@docker-server1 pods]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx 2/2 Running 0 36s 10.244.2.7 192.168.132.133 <none> <none>
Port mapping, two ways to access
[root@docker-server1 pods]# curl http://192.168.132.133:8080
[root@docker-server1 pods]# curl http://10.244.2.7
2.5 view details of pods
[root@docker-server1 pods]# kubectl describe po nginx
Name: nginx Namespace: default Priority: 0 Node: 192.168.132.133/192.168.132.133 Start Time: Thu, 09 Jan 2020 18:17:48 -0500 Labels: app=nginx Annotations: test: this is a test app Status: Running IP: 10.244.2.7 IPs: IP: 10.244.2.7 Containers: nginx: Container ID: docker://676a2d9bebda40d86138190093d1a6d6cf6f16e5ff0e89fc22df53a74bdf8048 Image: nginx Image ID: docker-pullable://nginx@sha256:8aa7f6a9585d908a63e5e418dc5d14ae7467d2e36e1ab4f0d8f9d059a3d071ce Port: 80/TCP Host Port: 8080/TCP State: Running Started: Thu, 09 Jan 2020 18:17:55 -0500 Ready: True Restart Count: 0 Environment: test: aaa test1: bbb Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-bwbrn (ro) busybox: Container ID: docker://e8cc006f3ab292701d9876d84881af90f4c97ea22f32bf0cabf2b93d82b8c82b Image: busybox Image ID: docker-pullable://busybox@sha256:6915be4043561d64e0ab0f8f098dc2ac48e077fe23f488ac24b665166898115a Port: <none> Host Port: <none> Command: sh -c sleep 3600 State: Running Started: Thu, 09 Jan 2020 18:18:00 -0500 Ready: True Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-bwbrn (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-bwbrn: Type: Secret (a volume populated by a Secret) SecretName: default-token-bwbrn Optional: false QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Pulling 4m43s kubelet, 192.168.132.133 Pulling image "nginx" Normal Scheduled 4m41s default-scheduler Successfully assigned default/nginx to 192.168.132.133 Normal Pulled 4m38s kubelet, 192.168.132.133 Successfully pulled image "nginx" Normal Created 4m37s kubelet, 192.168.132.133 Created container nginx Normal Started 4m37s kubelet, 192.168.132.133 Started container nginx Normal Pulling 4m37s kubelet, 192.168.132.133 Pulling image "busybox" Normal Pulled 4m32s kubelet, 192.168.132.133 Successfully pulled image "busybox" Normal Created 4m32s kubelet, 192.168.132.133 Created container busybox Normal Started 4m32s kubelet, 192.168.132.133 Started container busybox
Three yaml file back
If you accidentally delete a file yaml, you can retrieve descriptive information
3.1 yaml delete files
[root@docker-server1 pods]# rm -rf nginx-pods.yaml
[root@docker-server1 pods]# kubectl get pods nginx -o yaml
apiVersion: v1 kind: Pod metadata: annotations: test: this is a test app creationTimestamp: "2020-01-09T23:17:51Z" labels: app: nginx name: nginx namespace: default resourceVersion: "43864" selfLink: /api/v1/namespaces/default/pods/nginx uid: 41510342-de97-4b37-ab95-0a01dd73aac7 spec: containers: - env: - name: test value: aaa - name: test1 value: bbb image: nginx imagePullPolicy: Always name: nginx ports: - containerPort: 80 hostPort: 8080 protocol: TCP resources: {} terminationMessagePath: /dev/termination-log terminationMessagePolicy: File volumeMounts: - mountPath: /var/run/secrets/kubernetes.io/serviceaccount name: default-token-bwbrn readOnly: true - command: - sh - -c - sleep 3600 image: busybox imagePullPolicy: Always name: busybox resources: {} terminationMessagePath: /dev/termination-log terminationMessagePolicy: File volumeMounts: - mountPath: /var/run/secrets/kubernetes.io/serviceaccount name: default-token-bwbrn readOnly: true dnsPolicy: ClusterFirst enableServiceLinks: true nodeName: 192.168.132.133 priority: 0 restartPolicy: Always schedulerName: default-scheduler securityContext: {} serviceAccount: default serviceAccountName: default terminationGracePeriodSeconds: 30 tolerations: - effect: NoExecute key: node.kubernetes.io/not-ready operator: Exists tolerationSeconds: 300 - effect: NoExecute key: node.kubernetes.io/unreachable operator: Exists tolerationSeconds: 300 volumes: - name: default-token-bwbrn secret: defaultMode: 420 secretName: default-token-bwbrn status: conditions: - lastProbeTime: null lastTransitionTime: "2020-01-09T23:17:48Z" status: "True" type: Initialized - lastProbeTime: null lastTransitionTime: "2020-01-09T23:18:01Z" status: "True" type: Ready - lastProbeTime: null lastTransitionTime: "2020-01-09T23:18:01Z" status: "True" type: ContainersReady - lastProbeTime: null lastTransitionTime: "2020-01-09T23:17:51Z" status: "True" type: PodScheduled containerStatuses: - containerID: docker://e8cc006f3ab292701d9876d84881af90f4c97ea22f32bf0cabf2b93d82b8c82b image: busybox:latest imageID: docker-pullable://busybox@sha256:6915be4043561d64e0ab0f8f098dc2ac48e077fe23f488ac24b665166898115a lastState: {} name: busybox ready: true restartCount: 0 started: true state: running: startedAt: "2020-01-09T23:18:00Z" - containerID: docker://676a2d9bebda40d86138190093d1a6d6cf6f16e5ff0e89fc22df53a74bdf8048 image: nginx:latest imageID: docker-pullable://nginx@sha256:8aa7f6a9585d908a63e5e418dc5d14ae7467d2e36e1ab4f0d8f9d059a3d071ce lastState: {} name: nginx ready: true restartCount: 0 started: true state: running: startedAt: "2020-01-09T23:17:55Z" hostIP: 192.168.132.133 phase: Running podIP: 10.244.2.7 podIPs: - ip: 10.244.2.7 qosClass: BestEffort startTime: "2020-01-09T23:17:48Z"
3.2 Use command to recover
[root@docker-server1 pods]# kubectl get pods nginx -o yaml > nginx-pods.yaml
Remove unnecessary information
[root@docker-server1 pods]# vim nginx-pods.yaml
apiVersion: v1 kind: Pod metadata: annotations: test: this is a test app labels: app: nginx name: nginx namespace: default spec: containers: - env: - name: test value: aaa - name: test1 value: bbb image: nginx imagePullPolicy: Always name: nginx ports: - containerPort: 80 hostPort: 8080 protocol: TCP - command: - sh - -c - sleep 3600 image: busybox imagePullPolicy: Always name: busybox restartPolicy: Always
[root@docker-server1 pods]# kubectl delete pod nginx
[root@docker-server1 pods]# kubectl create -f nginx-pods.yaml
3.3 In accordance with the validation file recovery yaml
[root@docker-server1 pods]# kubectl get pods
NAME READY STATUS RESTARTS AGE nginx 2/2 Running 0 14s
[root@docker-server1 pods]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES nginx 2/2 Running 0 27s 10.244.2.8 192.168.132.133 <none> <none>
[root@docker-server1 pods]# curl http://192.168.132.133:8080
[root@docker-server1 pods]# curl http://10.244.2.8
<!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>
The pod is simple to learn here
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