1. Overview of Kubectl

Kubectl is the command line tool of Kubernetes cluster, through Kubectl can manage the cluster itself, and can install and deploy containerized applications on the cluster. The syntax for running kubectl looks like this:

$ kubectl [command] [TYPE] [NAME] [flags]Copy the code

Here the command, TYPE, NAME and flags are:

• Comand: Specifies the operations to be performed on the resource, such as create, GET, Describe, and DELETE
• TYPE: Specifies the resource TYPE. The resource TYPE is sensitive and can be singular, plural, or abbreviated by the developer. Such as:

$ kubectl get pod pod1 
$ kubectl get pods pod1 
$ kubectl get po pod1Copy the code

• NAME: Specifies the NAME of the resource. The NAME is also case-sensitive. If the name is omitted, all resources are displayed, for example:

 $ kubectl get podsCopy the code

• Flags: Specifies optional parameters. For example, you can specify the address and port of the Kubernetes API Server using either -s or -server arguments.

In addition, you can get more information by running the kubectl help command.

1.1 Kubectl operation

As a command line tool of Kubernetes, Kubectl’s main responsibility is to operate the resource objects in the cluster, including the creation, deletion and view of the resource objects. The following table shows all of the operations supported by Kubectl, along with their syntax and description information:

1.2 Resource Object Types

In Kubernetes, there are a number of resource objects that developers and operations personnel can use to orchestrate containers. In the following table, are the resource object types supported by Kubectl, along with their abbreviated aliases:

1.3 Output Options

The default output format of Kubectl is plain text. You can specify the output format of the command through the -o or -output field.

$ kubectl [command] [TYPE] [NAME] -o=<output_format>Copy the code

2. Kubectl installation and deployment

2.1 The installationkubectl

1) Download Kubectl

Here is under the Windows installation, so download kubectl. Exe, download address: storage.googleapis.com/kubernetes-… .

Add the address of kubectl.exe to the Path of Windows environment variable.

Please refer to: the other operating systems, the installation kubectl kubernetes. IO/docs/tasks /…

2) Configure the Kubeconfig file

RKE deploys a local file in the same directory as the configuration file that contains kube configuration information to connect to the newly generated cluster.

By default, the kube configuration file is called.kube_config_cluster.yml. Copy this file to your local ~/.kube/config and you can use kubectl locally.

Note that the deployed local KUBE configuration name is associated with the cluster configuration file. For example, if you use a configuration file named mycluster.yml, the local kube configuration will be named.kube_config_mycluster.yml.

2.2 validation

Execute kubectl to obtain information about nodes:

$ kubectl get nodesCopy the code

3, Kubectl common command examples

Examples of common commands are provided in this section to help you quickly get to know and try Kubectl.

1) kubectl create command

This command creates a resource object from a file or stdin. Assuming there is a YAML configuration file for nginx deployment, you can create the deployment object by executing the following command.

$ kubectl create -f nginx-deployment.yamlCopy the code

ApiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2 kind: Deployment metadata: name: nginx spec: replicas: 10 selector: matchLabels: app: nginx revisionHistoryLimit: 2 template: metadata: labels: app: nginx spec: ImagePullSecrets: - name: dC-hSPFD containers: # imagePullPolicy: nginx imagePullPolicy: Name: nginx80 # volumeMounts: - mountPath: /usr/share/nginx/html name: nginx-data-mountpath: /etc/nginx name: nginx-conf volumes: # Host directory Nginx-data NFS: path: /k8s-nfs/nginx server: 192.168.8.150 - name: nginx-conf NFS: path: /k8s-nfs/nginx/conf server: 192.168.8.150Copy the code

2) kubectl get

Use this command to list one or more resource objects, where all deployments under the default namespace are obtained using the kubectl get command.

3) Kubectl describe command

This command is used to display the details of one or more resource objects, in this case by obtaining the above nginx deployment information.

$ kubectl describe deployments/nginxCopy the code

4) kubectl exec command

This command is used to execute a command on a Pod container, where the /bin/bash command is executed on an nginx container.

$ kubectl exec -it nginx-5847748bf9-49k5k /bin/bashCopy the code

Kubectl logs

This command is used to obtain the log information of a Pod container.

$ kubectl logs nginx-5847748bf9-49k5kCopy the code

6) kubectl delete command

This command is used to delete an existing resource object from a cluster by specifying a name, label selector, or resource selector. Delete the nginx deployment you created earlier here.

$ kubectl delete deployments/nginxCopy the code

The resources

1. The kubectl Usage Conventions address: https://kubernetes.io/docs/reference/kubectl/conventions/

2. The kubectl Commands address: https://kubernetes.io/docs/reference/kubectl/kubectl-cmds/

3. “the Overview of kubectl address: https://kubernetes.io/docs/reference/kubectl/overview/

About the author: Ji Xiangyuan, product manager of Beijing Shenzhou Aerospace Software Technology Co., LTD. The copyright of this article belongs to the author.