Main kubectl commands

CLI Tool to interact with our K8s cluster

In order for kubectl to access a K8s cluster, it needs a kubeconfig file, which is created automatically when deploying our minikube cluster

By default, config file is located at ~/.kube/config

kubectl api-versions − It prints the supported versions of API on the cluster.

$ kubectl api-version;

kubectl apply − It has the capability to configure a resource by file or stdin.

$ kubectl apply –f <filename>

kubectl attach − This attaches things to the running container.

$ kubectl attach <pod> –c <container>
$ kubectl attach 123456-7890 -c tomcat-conatiner

kubectl autoscale − This is used to auto scale pods which are defined such as Deployment, replica set, Replication Controller.

$ kubectl autoscale (-f FILENAME | TYPE NAME | TYPE/NAME) [--min = MINPODS] --
max = MAXPODS [--cpu-percent = CPU] [flags]
$ kubectl autoscale deployment foo --min = 2 --max = 10

kubectl cluster-info − It displays the cluster Info.

$ kubectl cluster-info

kubectl cluster-info dump − It dumps relevant information regarding cluster for debugging and diagnosis.

$ kubectl cluster-info dump
$ kubectl cluster-info dump --output-directory = /path/to/cluster-state

kubectl config − Modifies the kubeconfig file.

$ kubectl config <SUBCOMMAD>
$ kubectl config –-kubeconfig <String of File name>

kubectl config current-context − It displays the current context.

$ kubectl config current-context
#deploys the current context

kubectl config delete-cluster − Deletes the specified cluster from kubeconfig.

$ kubectl config delete-cluster <Cluster Name>

kubectl config delete-context − Deletes a specified context from kubeconfig.

$ kubectl config delete-context <Context Name>

kubectl config get-clusters − Displays cluster defined in the kubeconfig.

$ kubectl config get-cluster
$ kubectl config get-cluster <Cluser Name>

kubectl config get-contexts − Describes one or many contexts.

$ kubectl config get-context <Context Name>

kubectl config set-cluster − Sets the cluster entry in Kubernetes.

$ kubectl config set-cluster NAME [--server = server] [--certificateauthority =
path/to/certificate/authority] [--insecure-skip-tls-verify = true]

kubectl config set-context − Sets a context entry in kubernetes entrypoint.

$ kubectl config set-context NAME [--cluster = cluster_nickname] [--
user = user_nickname] [--namespace = namespace]
$ kubectl config set-context prod –user = vipin-mishra

kubectl config set-credentials − Sets a user entry in kubeconfig.

$ kubectl config set-credentials cluster-admin --username = vipin --
password = uXFGweU9l35qcif

kubectl config set − Sets an individual value in kubeconfig file.

$ kubectl config set PROPERTY_NAME PROPERTY_VALUE

kubectl config unset − It unsets a specific component in kubectl.

$ kubectl config unset PROPERTY_NAME PROPERTY_VALUE

kubectl config use-context − Sets the current context in kubectl file.

$ kubectl config use-context <Context Name>

kubectl config view

$ kubectl config view
$ kubectl config view –o jsonpath='{.users[?(@.name == "e2e")].user.password}'

kubectl cp − Copy files and directories to and from containers.

$ kubectl cp <Files from source> <Files to Destinatiion>
$ kubectl cp /tmp/foo <some-pod>:/tmp/bar -c <specific-container>

kubectl create − To create resource by filename of or stdin. To do this, JSON or YAML formats are accepted.

$ kubectl create –f <File Name>
$ cat <file name> | kubectl create –f -

In the same way, we can create multiple things as listed using the create command along with kubectl.

• deployment

• namespace

• quota

• secret docker-registry

• secret

• secret generic

• secret tls

• serviceaccount

• service clusterip

• service loadbalancer

• service nodeport

kubectl delete − Deletes resources by file name, stdin, resource and names.

$ kubectl delete –f ([-f FILENAME] | TYPE [(NAME | -l label | --all)])

kubectl describe − Describes any particular resource in kubernetes. Shows details of resource or a group of resources.

$ kubectl describe <type> <type name>
$ kubectl describe pod tomcat

kubectl drain − This is used to drain a node for maintenance purpose. It prepares the node for maintenance. This will mark the node as unavailable so that it should not be assigned with a new container which will be created.

$ kubectl drain tomcat –force

kubectl edit − It is used to end the resources on the server. This allows to directly edit a resource which one can receive via the command line tool.

$ kubectl edit <Resource/Name | File Name)
Ex.
$ kubectl edit rc/tomcat

kubectl exec − This helps to execute a command in the container.

$ kubectl exec POD <-c CONTAINER > -- COMMAND < args...>
$ kubectl exec tomcat 123-5-456 date

kubectl expose − This is used to expose the Kubernetes objects such as pod, replication controller, and service as a new Kubernetes service. This has the capability to expose it via a running container or from a yaml file.

$ kubectl expose (-f FILENAME | TYPE NAME) [--port=port] [--protocol = TCP|UDP]
[--target-port = number-or-name] [--name = name] [--external-ip = external-ip-ofservice]
[--type = type]
$ kubectl expose rc tomcat –-port=80 –target-port = 30000
$ kubectl expose –f tomcat.yaml –port = 80 –target-port =

kubectl get − This command is capable of fetching data on the cluster about the Kubernetes resources.

$ kubectl get [(-o|--output=)json|yaml|wide|custom-columns=...|custom-columnsfile=...|
go-template=...|go-template-file=...|jsonpath=...|jsonpath-file=...]
(TYPE [NAME | -l label] | TYPE/NAME ...) [flags]

For example,

$ kubectl get pod <pod name>
$ kubectl get service <Service name>

kubectl logs − They are used to get the logs of the container in a pod. Printing the logs can be defining the container name in the pod. If the POD has only one container there is no need to define its name.

$ kubectl logs [-f] [-p] POD [-c CONTAINER]
Example
$ kubectl logs tomcat.
$ kubectl logs –p –c tomcat.8

kubectl port-forward − They are used to forward one or more local port to pods.

$ kubectl port-forward POD [LOCAL_PORT:]REMOTE_PORT
[...[LOCAL_PORT_N:]REMOTE_PORT_N]
$ kubectl port-forward tomcat 3000 4000
$ kubectl port-forward tomcat 3000:5000

kubectl replace − Capable of replacing a resource by file name or stdin.

$ kubectl replace -f FILENAME
$ kubectl replace –f tomcat.yml
$ cat tomcat.yml | kubectl replace –f -

kubectl rolling-update − Performs a rolling update on a replication controller. Replaces the specified replication controller with a new replication controller by updating a POD at a time.

$ kubectl rolling-update OLD_CONTROLLER_NAME ([NEW_CONTROLLER_NAME] --
image = NEW_CONTAINER_IMAGE | -f NEW_CONTROLLER_SPEC)
$ kubectl rolling-update frontend-v1 –f freontend-v2.yaml

kubectl rollout − It is capable of managing the rollout of deployment.

$ Kubectl rollout <Sub Command>
$ kubectl rollout undo deployment/tomcat

Apart from the above, we can perform multiple tasks using the rollout such as −

• rollout history

• rollout pause

• rollout resume

• rollout status

• rollout undo

kubectl run − Run command has the capability to run an image on the Kubernetes cluster.

$ kubectl run NAME --image = image [--env = "key = value"] [--port = port] [--
replicas = replicas] [--dry-run = bool] [--overrides = inline-json] [--command] --
[COMMAND] [args...]
$ kubectl run tomcat --image = tomcat:7.0
$ kubectl run tomcat –-image = tomcat:7.0 –port = 5000

kubectl scale − It will scale the size of Kubernetes Deployments, ReplicaSet, Replication Controller, or job.

$ kubectl scale [--resource-version = version] [--current-replicas = count] --
replicas = COUNT (-f FILENAME | TYPE NAME )
$ kubectl scale –-replica = 3 rs/tomcat
$ kubectl scale –replica = 3 tomcat.yaml

kubectl set image − It updates the image of a pod template.

$ kubectl set image (-f FILENAME | TYPE NAME)
CONTAINER_NAME_1 = CONTAINER_IMAGE_1 ... CONTAINER_NAME_N = CONTAINER_IMAGE_N
$ kubectl set image deployment/tomcat busybox = busybox ngnix = ngnix:1.9.1
$ kubectl set image deployments, rc tomcat = tomcat6.0 --all

kubectl set resources − It is used to set the content of the resource. It updates resource/limits on object with pod template.

$ kubectl set resources (-f FILENAME | TYPE NAME) ([--limits = LIMITS & --
requests = REQUESTS]
$ kubectl set resources deployment tomcat -c = tomcat --
limits = cpu = 200m,memory = 512Mi

kubectl top node − It displays CPU/Memory/Storage usage. The top command allows you to see the resource consumption for nodes.

$ kubectl top node [node Name]

The same command can be used with a pod as well.