Main points:
1. Overview of kubectl
2. kubectl syntax
3. kubectl Management Commands
4. Similarities and differences between create and apply commands
5. Example demonstration
1. Overview of kubectl

Kubectl is a command line interface for running commands against the Kubernetes cluster.The configuration file for Kubectl is in the $HOME/.kube directory.We can specify a kubeconfig file in another location by setting the KUBECONFIG environment variable or the command parameter, kubeconfig.

2. kubectl Syntax

1. Run the command from the terminal window using the following syntax, kubectl:

kubectl [command] [TYPE] [NAME] [flags]

2. where command, TYPE, NAME, and flags are:

• command

Specify the operations to be performed on one or more resources, such as create, get, describe, delete.For example, "kubectl get cs".

• TYPE

Specify the resource type.Resource types are case-insensitive and can be singular, plural, or abbreviated.

Example:

#The following commands produce the same output
kubectl get pod pod1

kubectl get pods pod1

kubectl get po pod1

• NAME

  Specify the name of the resource.Names are case sensitive.If the name is omitted, details of all resources, such as "kubectl get pods", are displayed.
  When working with multiple resources, we can specify each resource by type and name, or one or more files:

1. To specify resources by type and name:

• If the resource types are the same, group the resources:

TYPE1 name1 name2 name<#>. 

Example:

kubectl get pod example-pod1 example-pod2

• Specify multiple resource types:

TYPE1/name1 TYPE1/name2 TYPE2/name3 TYPE<#>/name<#>. 

Example:

kubectl get pod/example-pod1 replicationcontroller/example-rc1

2. To specify resources using one or more files:

-f file1 -f file2 -f file<#>
#Be aware of using YAML instead of JSON, as YAML is often more user-friendly, especially for configuration files.

Example:

kubectl get pod -f ./pod.yaml

• flags:

The optional flag specified, but it is worth noting that specifying parameters using the command line overrides the default values and associated environment variables.
For example, we can use the -s or--server flag to specify the address and port of the Kubernetes API server.

3. kubectl Management Commands

4. Similarities and differences between create and apply commands

• Create from YAML file

kubectl create -f FILENAME [options]

• Upgrade deployment through YAML file

kubectl apply -f FILENAME

• Same point

If the kind value in the yaml file is deployment, both commands above can create a deployment and generate the appropriate number of pod s

• Difference

create command: delete all existing things first, and regenerate new ones from the yaml file.So the configuration in the yaml file must be complete
 apply command: Upgrade an existing one according to what is listed in the configuration file.So the contents of the yaml file can only write attributes that need to be upgraded

5. Example demonstration:

• Life cycle of project

  Create->Publish->Update->Rollback->Delete

1. Create nginx

#Common syntax: kubectl run NAME --image=image [--env="key=value" parameter] [--port=port port] [--replicas=replicas replicas replicas set] [--dry-run=bool state] [--overrides=inline-json] [--command command] -- [COMMAND] [args...] [options]`
kubectl run nginx-deployment --image=nginx --port=80 --replicas=3

#View pod nodes
kubectl get pods

2. Publish nginx service to provide load balancing

#Common syntax: kubectl expose (-f FILENAME | TYPE NAME) [--port=port f or internal communication between port clusters] [--protocol=TCP|UDP|SCTP] [--target-port exposed port=number-or-name] [--name=name specified name] [--name=name specified name] [--external-ip=external-ip-of-service] [--type=type specified type] [options]
kubectl expose deployment nginx-deployment --port=80 --target-port=80 --name=nginx-deployment-service --type=NodePort

#View service publication, abbreviation of svc bit service component here
kubectl get pods,svc

#View Backend Associated Nodes
kubectl get endpoints

#View network status details
kubectl get pods -o wide

#View ports for services
kubectl get svc

#kube-proxy supports three modes in kubernetes. Before v1.8 we used iptables and userspace, and after kubernetes 1.8 we introduced ipvs

#Node node installs ipvsadmin tool to view service ports
yum install ipvsadm -y

ipvsadm -L -n
#Looking at it with the tool, you can see that the scheduling algorithm is rr polling mode

#View access log on master side
kubectl get pods

3. Update nginx version 1.14

• Google Browser reloads the refresh page to view nginx version information

View nginx version steps: F12 opens developer options - > F5 refresh access - > Find Network - > Click name - > Find headers header information

kubectl set image deployment/nginx-deployment nginx-deployment=nginx:1.14

4. Rollback nginx

#View historical versions
kubectl rollout history deployment/nginx-deployment

#Execute rollback to previous version
kubectl rollout undo deployment/nginx-deployment

#Check rollback status
kubectl rollout status deployment/nginx-deployment

5. Delete nginx

#Delete deployment
kubectl delete deployment/nginx-deployment

#Delete Service SVC
kubectl get svc

6. Other Commands

• View details of specific resources

kubectl describe (-f FILENAME | TYPE [NAME_PREFIX | -l label] | TYPE/NAME) [options]

• View deployment resources

kubectl describe deployment/nginx-deployment

• View resource object abbreviations

kubectl api-resources

• Enter the corresponding pod

kubectl exec POD [-c CONTAINER] -- COMMAND [args...] [options]

• View the resulting YAML format file

kubectl run nginx-deployment --image=nginx --port=80 --replicas=3 --dry-run -o yaml

• View the generated JSON format file

kubectl run nginx-deployment --image=nginx --port=80 --replicas=3 --dry-run -o json

• Generate YAML, JSON file export

kubectl run nginx-deployment --image=nginx --port=80 --replicas=3 --dry-run -o json(yaml) > test.json(yaml)

• Export existing resources

kubectl get svc/nginx-svc --export -o yaml > nginx-svc.yaml

• Test command correctness, do not execute (like sh-n in shell scripts)

kubectl run nginx --image=nginx --port=80 --replicas=2 --dry-run