1. Introduction to kubectl
kubectl is a command-line tool for operating k8s cluster, installed on the master node of k8s, using kubectl it will look for a file named config in the $HOME/.kube directory, you can set the Kubeconfig environment variable or set a specific kubeconfig, kubectl can also operate k8s clusters using specific kubeconfig files.
By interacting with the apiserver, kubectl can add, delete, modify, and check various resources in the k8s cluster. The following will introduce kubectl syntax, command line operations, and introduce common examples. Command details, parameters, and subcommands can be viewed in the kubectl reference documentation.
1.kubectl syntax
The kubectl syntax format is as follows, which can be executed on the master node of the k8s cluster: kubectl [command] [TYPE] [NAME] [flags]
2. Explanation of the above syntax
command: Specifies the operation to be performed on one or more resources, such as create, get, describe, delete, etc.
type: Specifies the resource type, which can be pod, deployment, statefulset, service, etc. Resource types are not case-sensitive and can be specified in singular, plural, or abbreviated forms. For example, the following command outputs the same result:
kubectl get pod pod1
kubectl get pods pod1
kubectl get po pod1
NAME: Specifies the name of the resource. Names are case sensitive. If the name is omitted, details for all resources are displayed: kubectl get pods.
flags: Specifies optional parameters. For example, you can use -o to see which machine a pod is on
Note: Arguments specified from the command line override default values and any corresponding environment variables.
3. Perform operations on multiple resources
Each resource can be specified by type, name, one or more files:
- Specify resources by type and name
To group all resources of the same type:
TYPE1 name1 name2 name<#>。
Example: kubectl get pod example-pod1 example-pod2
Specify multiple resource types separately:
TYPE1/name1 TYPE1/name2 TYPE2/name3 TYPE<#>/name<#>。
例：kubectl get pod/example-pod1 pod/example-pod2 deployment/example-rc1
[root@k8smaster ~]# kubectl get pods/tomcat-deploy-6b65dd5799-88676 deployment/tomcat-deploy
NAME READY STATUS RESTARTS AGE
pod/tomcat-deploy-6b65dd5799-88676 1/1 Running 5 2d21h
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/tomcat-deploy 0/2 2 0 2d21h
4.kubectl –-help
You can view the help commands of kubectl
Second, kubectl operation command demonstration
Reference: http://docs.kubernetes.org.cn/477.html
The following explains the commands and syntax related to kubectl operations:
annotate
- Description: Add or update comments for one or more resources.
Annotations are composed of key/value. The purpose of Annotations is to store auxiliary data, especially the data operated by tools and system extensions. If –overwrite is true, existing annotations can be overwritten. Otherwise, attempting to overwrite annotations will result in an error. If set If --resource-version is specified, the update will use this resource version, otherwise it will use the original resource version.
- grammar:
kubectl annotate (-f FILENAME | TYPE NAME | TYPE/NAME) KEY_1=VAL_1 … KEY_N=VAL_N [–overwrite] [–all] [–resource-version=version] [flags]
- Example:
Update the "kubectl-pod" pod and set the value of the annotation "description" to "my kubectl-pod". If the same annotation is set multiple times, only the last set value will be used.
kubectl annotate pods kubectl-pod description=‘my kubectl-pod’
Update the pod "kubectl-pod", set the value of annotation "description" to "my tomcat", overwriting the existing value
kubectl annotate --overwrite pods kubectl-pod description=‘my tomcat’
[root@k8smaster ~]# kubectl annotate pods tomcat-deploy-6b65dd5799-88676 description='my kubectl-pod'
pod/tomcat-deploy-6b65dd5799-88676 annotated
[root@k8smaster ~]# kubectl describe pods tomcat-deploy-6b65dd5799-88676
Name: tomcat-deploy-6b65dd5799-88676
Namespace: default
Priority: 0
Node: k8snode1/192.168.11.136
Start Time: Thu, 11 Aug 2022 02:17:38 -0700
Labels: app=tomcat
pod-template-hash=6b65dd5799
release=canary
Annotations: cni.projectcalico.org/podIP: 10.244.249.28/32
cni.projectcalico.org/podIPs: 10.244.249.28/32
description: my kubectl-pod
api-versions
- grammar:
kubectl api-versions [flags]
-
Description: List available api versions
-
The meaning of various apiVersion:
alpha: internal beta version, contains many bugs, there may be bugs in use, if this version is abandoned, customers will not be notified
eta: public beta version, this version can be used normally after a lot of testing, some details may change, But this version stable will not be abandoned
: Stable version: This version is very stable and can be used with confidence. Subsequent versions will always include this stable version, named like v1
- The results displayed by kubectl api-versions are as follows
admissionregistration.k8s.io/v1 #Admission control related api
v1 # Stable version of Kubernetes API, contains many core objects: pod, service, etc.
apps/v1 #Contains some common application layer api combinations, such as: Deployments, Statefulset, Daemonset, etc.
[root@k8smaster ~]# kubectl api-versions
admissionregistration.k8s.io/v1
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1
apiextensions.k8s.io/v1beta1
apply
- grammar:
kubectl apply -f FILENAME [flags]
Make changes to the resource's application configuration from a file. Declarative update configuration files.
autoscale
Autoscales a set of pods managed by a replica controller.
- grammar:
kubectl autoscale (-f FILENAME | TYPE NAME | TYPE/NAME) [–min=MINPODS] --max=MAXPODS [–cpu-percent=CPU] [flags]
cluster-info
- grammar:
kubectl cluster-info [flags] Displays endpoint information about masters and services in the cluster.
[root@k8smaster ~]# kubectl cluster-info
Kubernetes control plane is running at https://192.168.11.129:6443
KubeDNS is running at https://192.168.11.129:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
Metrics-server is running at https://192.168.11.129:6443/api/v1/namespaces/kube-system/services/https:metrics-server:/proxy
config
- grammar:
kubectl config SUBCOMMAND [flags] Modify kubeconfig file
create, generally not used, use apply instead of this
- grammar:
kubectl create -f FILENAME [flags] Create one or more resources from a file or standard input.
delete
- grammar:
kubectl delete (-f FILENAME | TYPE [NAME | /NAME | -l label | --all]) [flags] Delete a resource from file, standard input, or the specified label selector, name, resource selector, or resource.
[root@k8smaster ~]# kubectl delete deployment tomcat-deploy
deployment.apps "tomcat-deploy" deleted
describe
- grammar:
kubectl describe (-f FILENAME | TYPE [NAME_PREFIX | /NAME | -l label]) [flags] Display detailed status of one or more resources.
[root@k8smaster ~]# kubectl describe pods tomcat-deploy-6b65dd5799-88676
[root@k8smaster ~]# kubectl describe pod/tomcat-deploy-6b65dd5799-88676
edit
- grammar:
kubectl edit (-f FILENAME | TYPE NAME | TYPE/NAME) [flags] Use the default editor to edit and update the definition of one or more resources on the server, changing dynamically.
exec
- grammar:
kubectl exec POD-name [-c CONTAINER-name] [-i] [-t] [flags] [-- COMMAND [args…]] Execute a command for the containers in the pod.
The following command is the command to log in to the container in the pod, -c is the name of the container, if there is only one, you don't need to write it.
kubectl exec calico-node-cblk2 -n kube-system -i -t – /bin/sh
explain
- grammar:
kubectl explain [–recursive=false] [flags] Get documentation for various resources. For example, pod, node, service, etc. are equivalent to help commands, which can tell us how
to create resources
expose
- grammar:
kubectl expose (-f FILENAME | TYPE NAME | TYPE/NAME) [–port=port] [–protocol=TCP|UDP] [–target-port=number-or-name] [–name=name] [–externalip= external-ip-of-service] [–type=type] [flags] Expose the replica controller, service or pod as a new Kubernetes service.
get
- grammar:
kubectl get (-f FILENAME | TYPE [NAME | /NAME | -l label]) [–watch] [–sortby=FIELD] [[-o | --output]=OUTPUT_FORMAT] [flags]
List one or more resource.
label
- grammar:
kubectl label (-f FILENAME | TYPE NAME | TYPE/NAME) KEY_1=VAL_1 … KEY_N=VAL_N [–overwrite] [–all] [–resource-version=version] [flags] Add or update labels for one or more resources .
[root@k8smaster ~]# kubectl label pods tomcat-deploy-6b65dd5799-88676 a=b
pod/tomcat-deploy-6b65dd5799-88676 labeled
logs
- grammar:
kubectl logs POD [-c CONTAINER] [–follow] [flags] Print the log of the container, -c can specify the container
[root@k8smaster ~]# kubectl logs tomcat-deploy-6b65dd5799-88676
patch
- grammar:
kubectl patch (-f FILENAME | TYPE NAME | TYPE/NAME) --patch PATCH [flags] Update one or more fields of the resource
port-forward
1) Syntax:
kubectl port-forward POD [LOCAL_PORT:]REMOTE_PORT […[LOCAL_PORT_N:]REMOTE_PORT_N] [flags] Forward one or more local ports to the Pod.
proxy
- grammar:
kubectl proxy [–port=PORT] [–www=static-dir] [–www-prefix=prefix] [–apiprefix=prefix] [flags] Proxy to run the Kubernetes API server.
replace
- Syntax: kubectl replace -f FILENAM Replace resource from file or standard input.
run
- grammar:
kubectl run NAME --image=image [–env=“key=value”] [–port=port] [–dryrun=server | client | none] [–overrides=inline-json] [flags] Run the specified on the cluster mirror
kubectl run nginx --image=nginx
You can create an nginx application, and the actual creation of pod applications is created by writing a resource manifest file
scale
- grammar:
kubectl scale (-f FILENAME | TYPE NAME | TYPE/NAME) --replicas=COUNT [–resource-version=version] [–current-replicas=count] [flags] Update the size of the specified replica controller (change the number of replicas) .
version
- grammar:
kubectl version [–client] [flags] show the version of Kubernetes running on the client and server
Resource Type
The following table lists all supported resource types and their abbreviated aliases:
[root@k8smaster ~]# kubectl api-resources
NAME SHORTNAMES APIVERSION NAMESPACED KIND
bindings v1 true Binding
componentstatuses cs v1 false ComponentStatus
configmaps cm v1 true ConfigMap
endpoints ep v1 true Endpoints
events ev v1 true Event
limitranges limits v1 true LimitRange
namespaces ns v1 false Namespace
nodes no v1 false Node
persistentvolumeclaims pvc v1 true PersistentVolumeClaim
persistentvolumes pv v1 false PersistentVolume
pods po v1 true Pod
podtemplates v1 true PodTemplate
replicationcontrollers rc v1 true ReplicationController
resourcequotas quota v1 true ResourceQuota
secrets v1 true Secret
serviceaccounts sa v1 true ServiceAccount
services svc v1 true Service
mutatingwebhookconfigurations admissionregistration.k8s.io/v1 false MutatingWebhookConfiguration
validatingwebhookconfigurations admissionregistration.k8s.io/v1 false ValidatingWebhookConfiguration
customresourcedefinitions crd,crds apiextensions.k8s.io/v1 false CustomResourceDefinition
apiservices apiregistration.k8s.io/v1 false APIService
controllerrevisions apps/v1 true ControllerRevision
daemonsets ds apps/v1 true DaemonSet
deployments deploy apps/v1 true Deployment
replicasets rs apps/v1 true ReplicaSet
statefulsets sts apps/v1 true StatefulSet
tokenreviews authentication.k8s.io/v1 false TokenReview
localsubjectaccessreviews authorization.k8s.io/v1 true LocalSubjectAccessReview
selfsubjectaccessreviews authorization.k8s.io/v1 false SelfSubjectAccessReview
selfsubjectrulesreviews authorization.k8s.io/v1 false SelfSubjectRulesReview
subjectaccessreviews authorization.k8s.io/v1 false SubjectAccessReview
horizontalpodautoscalers hpa autoscaling/v1 true HorizontalPodAutoscaler
cronjobs cj batch/v1beta1 true CronJob
jobs batch/v1 true Job
certificatesigningrequests csr certificates.k8s.io/v1 false CertificateSigningRequest
leases coordination.k8s.io/v1 true Lease
bgpconfigurations crd.projectcalico.org/v1 false BGPConfiguration
bgppeers crd.projectcalico.org/v1 false BGPPeer
blockaffinities crd.projectcalico.org/v1 false BlockAffinity
clusterinformations crd.projectcalico.org/v1 false ClusterInformation
felixconfigurations crd.projectcalico.org/v1 false FelixConfiguration
globalnetworkpolicies crd.projectcalico.org/v1 false GlobalNetworkPolicy
globalnetworksets crd.projectcalico.org/v1 false GlobalNetworkSet
hostendpoints crd.projectcalico.org/v1 false HostEndpoint
ipamblocks crd.projectcalico.org/v1 false IPAMBlock
ipamconfigs crd.projectcalico.org/v1 false IPAMConfig
ipamhandles crd.projectcalico.org/v1 false IPAMHandle
ippools crd.projectcalico.org/v1 false IPPool
kubecontrollersconfigurations crd.projectcalico.org/v1 false KubeControllersConfiguration
networkpolicies crd.projectcalico.org/v1 true NetworkPolicy
networksets crd.projectcalico.org/v1 true NetworkSet
endpointslices discovery.k8s.io/v1beta1 true EndpointSlice
events ev events.k8s.io/v1 true Event
ingresses ing extensions/v1beta1 true Ingress
flowschemas flowcontrol.apiserver.k8s.io/v1beta1 false FlowSchema
prioritylevelconfigurations flowcontrol.apiserver.k8s.io/v1beta1 false PriorityLevelConfiguration
ingressclasses networking.k8s.io/v1 false IngressClass
ingresses ing networking.k8s.io/v1 true Ingress
networkpolicies netpol networking.k8s.io/v1 true NetworkPolicy
runtimeclasses node.k8s.io/v1 false RuntimeClass
poddisruptionbudgets pdb policy/v1beta1 true PodDisruptionBudget
podsecuritypolicies psp policy/v1beta1 false PodSecurityPolicy
clusterrolebindings rbac.authorization.k8s.io/v1 false ClusterRoleBinding
clusterroles rbac.authorization.k8s.io/v1 false ClusterRole
rolebindings rbac.authorization.k8s.io/v1 true RoleBinding
roles rbac.authorization.k8s.io/v1 true Role
priorityclasses pc scheduling.k8s.io/v1 false PriorityClass
csidrivers storage.k8s.io/v1 false CSIDriver
csinodes storage.k8s.io/v1 false CSINode
storageclasses sc storage.k8s.io/v1 false StorageClass
volumeattachments storage.k8s.io/v1 false VolumeAttachment
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