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Editor to share with you what the basic use of K8S, I believe that most people do not know much, so share this article for your reference, I hope you will learn a lot after reading this article, let's go to know it!

Pod creation

The smallest unit of a K8s cluster is pod. A pod can contain multiple containers, usually using a yaml file to create a pod, or directly using the run command.

Create pod: command format: kubectl create-f [yaml file] create directly using the RUN command: command format: kubectl run-I-t [pod name]-image= [image name]

Column 1: create a Redis-master pod from the ymal file

Redis-master-controller.yaml file content: apiVersion: v1kind: ReplicationControllermetadata: name: redis-master labels: name: redis-masterspec: replicas: selector: name: redis-master template: metadata: labels: name: redis-masterspec: containers:-name: master image: kubeguide/redis-master ports:-containerPort: 6379kubectl create-f redis-master-controller.yaml

Example 2: create directly using the RUN command

Kubectl run-I-t busybox-- image=busyboxkubectl run-I-t busybox-- image=busybox-- replicas=5-- replicas specify the number of copies commonly used parameters pod delete command format: kubectl delete pod/po [pod name]

At this point, although pod has been deleted, when you check the pod again, you will find that there is still a pod named busybox**. This is because of the security mechanism of K8s. K8s ensures a constant number of defined pod replicas. If you add a pod replica with a number of 5, then there are 5 pod to provide services. The security mechanism that pod breaks or deletes K8s will check the number of copies if the number of pod is less than 5, then K8s will automatically create pod to keep it at 5.

Completely delete:

The first way is to re-edit the yaml file if the file specifies multiple copies and change it to 0. The second way is to use the kubectl delete-f m command

POD View

Overall view

Command kubectl get pods to view

View relative details

Kubectl get pod-o wide

More detailed information

Command format: kubectl describe [po/deploy] [name] what are pod and deploymentpod

Pod is the smallest unit of a K8s cluster. A pod can contain multiple containers, so all containers belonging to this pod will run on one node. Pod encapsulates containers for one or more applications (such as nginx, etc.), storage resources, unique network IP, and some options for managing containers Pod marks a deployment unit, which can be understood as a single instance of an application in Kubernetes, which may consist of a single container or a small number of containers that are tightly coupled and share resources. If multiple containers share the same IP under the same Pod, they cannot have duplicate port numbers. For example, if you run two nginx under one Pod, there will be a container exception. Multiple containers under one Pod can use localhost to access each other's port. Pod is the smallest unit. If the container terminates abnormally in Pod, it will not restart. In actual use scenarios, you will not directly use Pod but use Deployment to deploy your own applications.

What is deployment?

In the previous version, Replication Controller was used to manage the number of Pod copies, but in the new version, it is officially recommended to use Deployment instead of RC,Deployment over RC.

Features:

Deployment has more flexible and powerful upgrade and rollback capabilities, and supports rolling updates

To upgrade Pod using Deployment, you only need to define the final state of Pod, and K8s will perform the necessary actions for you (RC has to define how to do it)

Enter the operation inside the container

The K8s entry pod instruction is similar to the docker entry container specification.

The instructions for Docker to enter the container are:

Docker exec-it container ID/name sh/bash

K8s enters the container in pod with the following instructions:

Kubectl exec-it pod-name sh/bash

Copy a file to the directory specified by pod

Command: kubectl cp file/dir: a directory service and pod or deployment

The relationship between pod and service

It was written earlier that POD was created, but the service is still not available with POD. At this time, it is our turn to play service. Professionally, we call the service release. Service publishing creates a POD or deployment and then needs to create a service to publish it. The association between pod and service is achieved through the labels tag. Multiple tags can be added for the accuracy of the association

Example: we create a POD for redis-master and then create a service for redis-master and publish

Publish pod

Create pod:vim redis-master-controller.yaml apiVersion: v1kind: ReplicationControllermetadata: name: redis-master labels: name: redis-masterspec: replicas: selector: name: redis-master template: metadata: labels: name: redis-masterspec: containers:-name: master image: kubeguide/redis-master ports:-containerPort: 6379

Publish Service

Vim redis-master-service.yaml apiVersion: v1kind: Servicemetadata: name: redis-master labels: name: redis-masterspec: ports:-port: 6379 targetPort: 6379 selector: name: redis-master service is created in the same way as pod: using kubectl create-f [x-service.yaml] kubectl create-f redis-master-service.yaml

View Servic

Command that the CLUSTER-IP of the kubectl get svc-o wide service is the VIP of the service

View detailed description information:

Kubectl describe svc [service-name]

Destroy service

The destruction of service is the same as that of pod. Command: kubectl delete-f [x-service.yaml]

Note: creating a complete container service includes POD (Deployment) and Services. It is recommended that Services be created before Pod.

Dynamic scaling of the number of Pod copies

Method 1 use the command to manipulate the number of copies

Example: create a redis-slave application container with the number of copies specified as 2, and then dynamically expand and reduce the capacity through the command

Vim redis-slave.yamlapiVersion: v1kind: ReplicationControllermetadata: name: redis-slave labels: name: redis-slavespec: replicas: 2 selector: name: redis-slave template: metadata: labels: name: redis-slavespec: containers:-name: slave image: kubeguide/guestbook-redis-slave env:-name: GET_HOSTS_FROM value: env ports:-containerPort: 6379kubectl create-f redis-slave.yaml

The above yaml file defines 2 copies of pod. We expand the capacity to 5 by command.

Use the scale command kubectl scale rc redis-slave-- replicas=5

At this point, check with the kubectl get pod-o wide command, and you will find that there are five redis-slave pod.

The way to scale down is also specified in the command-- the number of replicas can be achieved.

Method 2 modify configuration to achieve capacity reduction and expansion command: kubectl edit rc/deployment [rc/deployment-name]

Example: modify the application configuration we set the number of replicas to 5 in the previous step, and now change it to 6 to save and exit verification

Kubectl edit rc redis-slave

Method 3 modify yaml file reconstruction to achieve the purpose of reconstruction command: kubectl replace-f x.yaml

Modify the configuration file for refactoring, which is the process of releasing an existing pod and then creating a new pod

View the ports used by the services that have been built

View all of them, including the host

Command: kubectl get endpoints

View only rc/deploy-related ports

Kubectl get ep [rc/deploy-name]

Status of pod

Using k8s to create several states of pod

Pending:Pod has been received by the system and is ready to download the image. The Running:Pod has been assigned to the node and all containers have been created. At least one container is still running, starting, or restarting. All containers in Successed:Pod have been successfully terminated and will not be restarted. All containers in Failed:Pod have been terminated, and at least one container has been terminated. That is, the container exits a non-zero state or is terminated by the system. Unknown: for some reason, the Pod status cannot be obtained, usually due to an error communicating with the host where the Pod resides. Namespace

View all namespace

Command: kubectl get namespace/ns (ns is abbreviated)

Note: when we create a Pod without specifying namespace, we will use the default namespace by default.

Assign namespace to pod

Before assigning pod, our K8s cluster defaults to only default, so if we use other namespaces, we need to create namespaces first.

Example: create a namespace named mynamespace

The cat mynamespace.yamlapiVersion: v1kind: Namespacemetadata: name: mynamespace creation command is the same as creating pod and service

Yaml specifies the namespace indicator:

Cat pod.yamlapiVersion: v1kind: Podmetadata: name: busybox1 namespace: mynamespacespec: containers:-image: gcr.io/google_containers/busybox command:-sleep-"3600" name: busybox1kubectl create-f pod.yaml

After creating the pod, you can't see it when you use kubectl get pod-o wide or kubectl get pod to view it, because these pod are in the default space.

So if you want to view the pod of mynamespace space, you need to specify the namespace space in the view command.

Command:

Kubectl get pods-n [namespace name] or kubectl get pods-o wide-n [namespace name]

Use the run command to create a pod to specify the namespace

Kubectl run-I-t busybox-image=busybox-namespace=mynamespace

Kubectl Command Line Management object

Tips for creating resources

When a resource can be created using create, you can use-o yaml and-- dry-run to see how the yaml file is written

-o yaml output in yaml format

-- dry-run test creation, does not actually create resources

Example:

Kubectl create serviceaccount mycount-o yaml-- dry-run

Another method is to export a pod/deploy yaml file for template files that can be modified to other pod/deploy yaml

Kubectl get pods x-pod-o yaml-- export

View node tags

Kubectl get nodes-show-labels

Tag node

Kubectl label nodes node1 zone=foozone tag keyfoo tag value

Node set smudge

Kubectl taint node node2 node-type=dev:NoExecute

Node decontamination

Kubectl taint node node2 node-type:NoExecute- above is all the contents of this article entitled "what are the basic uses of K8S?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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