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Command line tool (kubectl)

Kubernetes provides a command line tool for communicating with a Kubernetes cluster's control plane, using the Kubernetes API.

This tool is named kubectl.

For configuration, kubectl looks for a file named config in the $HOME/.kube directory. You can specify other kubeconfig files by setting the KUBECONFIG environment variable or by setting the --kubeconfig flag.

This overview covers kubectl syntax, describes the command operations, and provides common examples. For details about each command, including all the supported flags and subcommands, see the kubectl reference documentation.

For installation instructions, see Installing kubectl; for a quick guide, see the cheat sheet. If you're used to using the docker command-line tool, kubectl for Docker Users explains some equivalent commands for Kubernetes.

Syntax

Use the following syntax to run kubectl commands from your terminal window:

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

where command, TYPE, NAME, and flags are:

  • command: Specifies the operation that you want to perform on one or more resources, for example create, get, describe, delete.

  • TYPE: Specifies the resource type. Resource types are case-insensitive and you can specify the singular, plural, or abbreviated forms. For example, the following commands produce the same output:

    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, for example kubectl get pods.

    When performing an operation on multiple resources, you can specify each resource by type and name or specify one or more files:

    • To specify resources by type and name:

      • To group resources if they are all the same type: TYPE1 name1 name2 name<#>.
        Example: kubectl get pod example-pod1 example-pod2

      • To specify multiple resource types individually: TYPE1/name1 TYPE1/name2 TYPE2/name3 TYPE<#>/name<#>.
        Example: kubectl get pod/example-pod1 replicationcontroller/example-rc1

    • To specify resources with one or more files: -f file1 -f file2 -f file<#>

      • Use YAML rather than JSON since YAML tends to be more user-friendly, especially for configuration files.
        Example: kubectl get -f ./pod.yaml
  • flags: Specifies optional flags. For example, you can use the -s or --server flags to specify the address and port of the Kubernetes API server.

If you need help, run kubectl help from the terminal window.

In-cluster authentication and namespace overrides

By default kubectl will first determine if it is running within a pod, and thus in a cluster. It starts by checking for the KUBERNETES_SERVICE_HOST and KUBERNETES_SERVICE_PORT environment variables and the existence of a service account token file at /var/run/secrets/kubernetes.io/serviceaccount/token. If all three are found in-cluster authentication is assumed.

To maintain backwards compatibility, if the POD_NAMESPACE environment variable is set during in-cluster authentication it will override the default namespace from the service account token. Any manifests or tools relying on namespace defaulting will be affected by this.

POD_NAMESPACE environment variable

If the POD_NAMESPACE environment variable is set, cli operations on namespaced resources will default to the variable value. For example, if the variable is set to seattle, kubectl get pods would return pods in the seattle namespace. This is because pods are a namespaced resource, and no namespace was provided in the command. Review the output of kubectl api-resources to determine if a resource is namespaced.

Explicit use of --namespace <value> overrides this behavior.

How kubectl handles ServiceAccount tokens

If:

  • there is Kubernetes service account token file mounted at /var/run/secrets/kubernetes.io/serviceaccount/token, and
  • the KUBERNETES_SERVICE_HOST environment variable is set, and
  • the KUBERNETES_SERVICE_PORT environment variable is set, and
  • you don't explicitly specify a namespace on the kubectl command line

then kubectl assumes it is running in your cluster. The kubectl tool looks up the namespace of that ServiceAccount (this is the same as the namespace of the Pod) and acts against that namespace. This is different from what happens outside of a cluster; when kubectl runs outside a cluster and you don't specify a namespace, the kubectl command acts against the default namespace.

Operations

The following table includes short descriptions and the general syntax for all of the kubectl operations:

Operation Syntax Description
alpha kubectl alpha SUBCOMMAND [flags] List the available commands that correspond to alpha features, which are not enabled in Kubernetes clusters by default.
annotate kubectl annotate (-f FILENAME | TYPE NAME | TYPE/NAME) KEY_1=VAL_1 ... KEY_N=VAL_N [--overwrite] [--all] [--resource-version=version] [flags] Add or update the annotations of one or more resources.
api-resources kubectl api-resources [flags] List the API resources that are available.
api-versions kubectl api-versions [flags] List the API versions that are available.
apply kubectl apply -f FILENAME [flags] Apply a configuration change to a resource from a file or stdin.
attach kubectl attach POD -c CONTAINER [-i] [-t] [flags] Attach to a running container either to view the output stream or interact with the container (stdin).
auth kubectl auth [flags] [options] Inspect authorization.
autoscale kubectl autoscale (-f FILENAME | TYPE NAME | TYPE/NAME) [--min=MINPODS] --max=MAXPODS [--cpu-percent=CPU] [flags] Automatically scale the set of pods that are managed by a replication controller.
certificate kubectl certificate SUBCOMMAND [options] Modify certificate resources.
cluster-info kubectl cluster-info [flags] Display endpoint information about the master and services in the cluster.
completion kubectl completion SHELL [options] Output shell completion code for the specified shell (bash or zsh).
config kubectl config SUBCOMMAND [flags] Modifies kubeconfig files. See the individual subcommands for details.
convert kubectl convert -f FILENAME [options] Convert config files between different API versions. Both YAML and JSON formats are accepted. Note - requires kubectl-convert plugin to be installed.
cordon kubectl cordon NODE [options] Mark node as unschedulable.
cp kubectl cp <file-spec-src> <file-spec-dest> [options] Copy files and directories to and from containers.
create kubectl create -f FILENAME [flags] Create one or more resources from a file or stdin.
delete kubectl delete (-f FILENAME | TYPE [NAME | /NAME | -l label | --all]) [flags] Delete resources either from a file, stdin, or specifying label selectors, names, resource selectors, or resources.
describe kubectl describe (-f FILENAME | TYPE [NAME_PREFIX | /NAME | -l label]) [flags] Display the detailed state of one or more resources.
diff kubectl diff -f FILENAME [flags] Diff file or stdin against live configuration.
drain kubectl drain NODE [options] Drain node in preparation for maintenance.
edit kubectl edit (-f FILENAME | TYPE NAME | TYPE/NAME) [flags] Edit and update the definition of one or more resources on the server by using the default editor.
exec kubectl exec POD [-c CONTAINER] [-i] [-t] [flags] [-- COMMAND [args...]] Execute a command against a container in a pod.
explain kubectl explain [--recursive=false] [flags] Get documentation of various resources. For instance pods, nodes, services, etc.
expose kubectl expose (-f FILENAME | TYPE NAME | TYPE/NAME) [--port=port] [--protocol=TCP|UDP] [--target-port=number-or-name] [--name=name] [--external-ip=external-ip-of-service] [--type=type] [flags] Expose a replication controller, service, or pod as a new Kubernetes service.
get kubectl get (-f FILENAME | TYPE [NAME | /NAME | -l label]) [--watch] [--sort-by=FIELD] [[-o | --output]=OUTPUT_FORMAT] [flags] List one or more resources.
kustomize kubectl kustomize <dir> [flags] [options] List a set of API resources generated from instructions in a kustomization.yaml file. The argument must be the path to the directory containing the file, or a git repository URL with a path suffix specifying same with respect to the repository root.
label 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 the labels of one or more resources.
logs kubectl logs POD [-c CONTAINER] [--follow] [flags] Print the logs for a container in a pod.
options kubectl options List of global command-line options, which apply to all commands.
patch kubectl patch (-f FILENAME | TYPE NAME | TYPE/NAME) --patch PATCH [flags] Update one or more fields of a resource by using the strategic merge patch process.
plugin kubectl plugin [flags] [options] Provides utilities for interacting with plugins.
port-forward kubectl port-forward POD [LOCAL_PORT:]REMOTE_PORT [...[LOCAL_PORT_N:]REMOTE_PORT_N] [flags] Forward one or more local ports to a pod.
proxy kubectl proxy [--port=PORT] [--www=static-dir] [--www-prefix=prefix] [--api-prefix=prefix] [flags] Run a proxy to the Kubernetes API server.
replace kubectl replace -f FILENAME Replace a resource from a file or stdin.
rollout kubectl rollout SUBCOMMAND [options] Manage the rollout of a resource. Valid resource types include: deployments, daemonsets and statefulsets.
run kubectl run NAME --image=image [--env="key=value"] [--port=port] [--dry-run=server|client|none] [--overrides=inline-json] [flags] Run a specified image on the cluster.
scale kubectl scale (-f FILENAME | TYPE NAME | TYPE/NAME) --replicas=COUNT [--resource-version=version] [--current-replicas=count] [flags] Update the size of the specified replication controller.
set kubectl set SUBCOMMAND [options] Configure application resources.
taint kubectl taint NODE NAME KEY_1=VAL_1:TAINT_EFFECT_1 ... KEY_N=VAL_N:TAINT_EFFECT_N [options] Update the taints on one or more nodes.
top kubectl top [flags] [options] Display Resource (CPU/Memory/Storage) usage.
uncordon kubectl uncordon NODE [options] Mark node as schedulable.
version kubectl version [--client] [flags] Display the Kubernetes version running on the client and server.
wait kubectl wait ([-f FILENAME] | resource.group/resource.name | resource.group [(-l label | --all)]) [--for=delete|--for condition=available] [options] Experimental: Wait for a specific condition on one or many resources.

To learn more about command operations, see the kubectl reference documentation.

Resource types

The following table includes a list of all the supported resource types and their abbreviated aliases.

(This output can be retrieved from kubectl api-resources, and was accurate as of Kubernetes 1.19.1.)

NAME SHORTNAMES APIGROUP NAMESPACED KIND
bindings true Binding
componentstatuses cs false ComponentStatus
configmaps cm true ConfigMap
endpoints ep true Endpoints
events ev true Event
limitranges limits true LimitRange
namespaces ns false Namespace
nodes no false Node
persistentvolumeclaims pvc true PersistentVolumeClaim
persistentvolumes pv false PersistentVolume
pods po true Pod
podtemplates true PodTemplate
replicationcontrollers rc true ReplicationController
resourcequotas quota true ResourceQuota
secrets true Secret
serviceaccounts sa true ServiceAccount
services svc true Service
mutatingwebhookconfigurations admissionregistration.k8s.io false MutatingWebhookConfiguration
validatingwebhookconfigurations admissionregistration.k8s.io false ValidatingWebhookConfiguration
customresourcedefinitions crd,crds apiextensions.k8s.io false CustomResourceDefinition
apiservices apiregistration.k8s.io false APIService
controllerrevisions apps true ControllerRevision
daemonsets ds apps true DaemonSet
deployments deploy apps true Deployment
replicasets rs apps true ReplicaSet
statefulsets sts apps true StatefulSet
tokenreviews authentication.k8s.io false TokenReview
localsubjectaccessreviews authorization.k8s.io true LocalSubjectAccessReview
selfsubjectaccessreviews authorization.k8s.io false SelfSubjectAccessReview
selfsubjectrulesreviews authorization.k8s.io false SelfSubjectRulesReview
subjectaccessreviews authorization.k8s.io false SubjectAccessReview
horizontalpodautoscalers hpa autoscaling true HorizontalPodAutoscaler
cronjobs cj batch true CronJob
jobs batch true Job
certificatesigningrequests csr certificates.k8s.io false CertificateSigningRequest
leases coordination.k8s.io true Lease
endpointslices discovery.k8s.io true EndpointSlice
events ev events.k8s.io true Event
ingresses ing extensions true Ingress
flowschemas flowcontrol.apiserver.k8s.io false FlowSchema
prioritylevelconfigurations flowcontrol.apiserver.k8s.io false PriorityLevelConfiguration
ingressclasses networking.k8s.io false IngressClass
ingresses ing networking.k8s.io true Ingress
networkpolicies netpol networking.k8s.io true NetworkPolicy
runtimeclasses node.k8s.io false RuntimeClass
poddisruptionbudgets pdb policy true PodDisruptionBudget
podsecuritypolicies psp policy false PodSecurityPolicy
clusterrolebindings rbac.authorization.k8s.io false ClusterRoleBinding
clusterroles rbac.authorization.k8s.io false ClusterRole
rolebindings rbac.authorization.k8s.io true RoleBinding
roles rbac.authorization.k8s.io true Role
priorityclasses pc scheduling.k8s.io false PriorityClass
csidrivers storage.k8s.io false CSIDriver
csinodes storage.k8s.io false CSINode
storageclasses sc storage.k8s.io false StorageClass
volumeattachments storage.k8s.io false VolumeAttachment

Output options

Use the following sections for information about how you can format or sort the output of certain commands. For details about which commands support the various output options, see the kubectl reference documentation.

Formatting output

The default output format for all kubectl commands is the human readable plain-text format. To output details to your terminal window in a specific format, you can add either the -o or --output flags to a supported kubectl command.

Syntax

kubectl [command] [TYPE] [NAME] -o <output_format>

Depending on the kubectl operation, the following output formats are supported:

Output format Description
-o custom-columns=<spec> Print a table using a comma separated list of custom columns.
-o custom-columns-file=<filename> Print a table using the custom columns template in the <filename> file.
-o json Output a JSON formatted API object.
-o jsonpath=<template> Print the fields defined in a jsonpath expression.
-o jsonpath-file=<filename> Print the fields defined by the jsonpath expression in the <filename> file.
-o name Print only the resource name and nothing else.
-o wide Output in the plain-text format with any additional information. For pods, the node name is included.
-o yaml Output a YAML formatted API object.
Example

In this example, the following command outputs the details for a single pod as a YAML formatted object:

kubectl get pod web-pod-13je7 -o yaml

Remember: See the kubectl reference documentation for details about which output format is supported by each command.

Custom columns

To define custom columns and output only the details that you want into a table, you can use the custom-columns option. You can choose to define the custom columns inline or use a template file: -o custom-columns=<spec> or -o custom-columns-file=<filename>.

Examples

Inline:

kubectl get pods <pod-name> -o custom-columns=NAME:.metadata.name,RSRC:.metadata.resourceVersion

Template file:

kubectl get pods <pod-name> -o custom-columns-file=template.txt

where the template.txt file contains:

NAME          RSRC
metadata.name metadata.resourceVersion

The result of running either command is similar to:

NAME           RSRC
submit-queue   610995

Server-side columns

kubectl supports receiving specific column information from the server about objects. This means that for any given resource, the server will return columns and rows relevant to that resource, for the client to print. This allows for consistent human-readable output across clients used against the same cluster, by having the server encapsulate the details of printing.

This feature is enabled by default. To disable it, add the --server-print=false flag to the kubectl get command.

Examples

To print information about the status of a pod, use a command like the following:

kubectl get pods <pod-name> --server-print=false

The output is similar to:

NAME       AGE
pod-name   1m

Sorting list objects

To output objects to a sorted list in your terminal window, you can add the --sort-by flag to a supported kubectl command. Sort your objects by specifying any numeric or string field with the --sort-by flag. To specify a field, use a jsonpath expression.

Syntax

kubectl [command] [TYPE] [NAME] --sort-by=<jsonpath_exp>
Example

To print a list of pods sorted by name, you run:

kubectl get pods --sort-by=.metadata.name

Examples: Common operations

Use the following set of examples to help you familiarize yourself with running the commonly used kubectl operations:

kubectl apply - Apply or Update a resource from a file or stdin.

# Create a service using the definition in example-service.yaml.
kubectl apply -f example-service.yaml

# Create a replication controller using the definition in example-controller.yaml.
kubectl apply -f example-controller.yaml

# Create the objects that are defined in any .yaml, .yml, or .json file within the <directory> directory.
kubectl apply -f <directory>

kubectl get - List one or more resources.

# List all pods in plain-text output format.
kubectl get pods

# List all pods in plain-text output format and include additional information (such as node name).
kubectl get pods -o wide

# List the replication controller with the specified name in plain-text output format. Tip: You can shorten and replace the 'replicationcontroller' resource type with the alias 'rc'.
kubectl get replicationcontroller <rc-name>

# List all replication controllers and services together in plain-text output format.
kubectl get rc,services

# List all daemon sets in plain-text output format.
kubectl get ds

# List all pods running on node server01
kubectl get pods --field-selector=spec.nodeName=server01

kubectl describe - Display detailed state of one or more resources, including the uninitialized ones by default.

# Display the details of the node with name <node-name>.
kubectl describe nodes <node-name>

# Display the details of the pod with name <pod-name>.
kubectl describe pods/<pod-name>

# Display the details of all the pods that are managed by the replication controller named <rc-name>.
# Remember: Any pods that are created by the replication controller get prefixed with the name of the replication controller.
kubectl describe pods <rc-name>

# Describe all pods
kubectl describe pods

kubectl delete - Delete resources either from a file, stdin, or specifying label selectors, names, resource selectors, or resources.

# Delete a pod using the type and name specified in the pod.yaml file.
kubectl delete -f pod.yaml

# Delete all the pods and services that have the label '<label-key>=<label-value>'.
kubectl delete pods,services -l <label-key>=<label-value>

# Delete all pods, including uninitialized ones.
kubectl delete pods --all

kubectl exec - Execute a command against a container in a pod.

# Get output from running 'date' from pod <pod-name>. By default, output is from the first container.
kubectl exec <pod-name> -- date

# Get output from running 'date' in container <container-name> of pod <pod-name>.
kubectl exec <pod-name> -c <container-name> -- date

# Get an interactive TTY and run /bin/bash from pod <pod-name>. By default, output is from the first container.
kubectl exec -ti <pod-name> -- /bin/bash

kubectl logs - Print the logs for a container in a pod.

# Return a snapshot of the logs from pod <pod-name>.
kubectl logs <pod-name>

# Start streaming the logs from pod <pod-name>. This is similar to the 'tail -f' Linux command.
kubectl logs -f <pod-name>

kubectl diff - View a diff of the proposed updates to a cluster.

# Diff resources included in "pod.json".
kubectl diff -f pod.json

# Diff file read from stdin.
cat service.yaml | kubectl diff -f -

Examples: Creating and using plugins

Use the following set of examples to help you familiarize yourself with writing and using kubectl plugins:

# create a simple plugin in any language and name the resulting executable file
# so that it begins with the prefix "kubectl-"
cat ./kubectl-hello
#!/bin/sh

# this plugin prints the words "hello world"
echo "hello world"

With a plugin written, let's make it executable:

chmod a+x ./kubectl-hello

# and move it to a location in our PATH
sudo mv ./kubectl-hello /usr/local/bin
sudo chown root:root /usr/local/bin

# You have now created and "installed" a kubectl plugin.
# You can begin using this plugin by invoking it from kubectl as if it were a regular command
kubectl hello
hello world
# You can "uninstall" a plugin, by removing it from the folder in your
# $PATH where you placed it
sudo rm /usr/local/bin/kubectl-hello

In order to view all of the plugins that are available to kubectl, use the kubectl plugin list subcommand:

kubectl plugin list

The output is similar to:

The following kubectl-compatible plugins are available:

/usr/local/bin/kubectl-hello
/usr/local/bin/kubectl-foo
/usr/local/bin/kubectl-bar

kubectl plugin list also warns you about plugins that are not executable, or that are shadowed by other plugins; for example:

sudo chmod -x /usr/local/bin/kubectl-foo # remove execute permission
kubectl plugin list
The following kubectl-compatible plugins are available:

/usr/local/bin/kubectl-hello
/usr/local/bin/kubectl-foo
  - warning: /usr/local/bin/kubectl-foo identified as a plugin, but it is not executable
/usr/local/bin/kubectl-bar

error: one plugin warning was found

You can think of plugins as a means to build more complex functionality on top of the existing kubectl commands:

cat ./kubectl-whoami

The next few examples assume that you already made kubectl-whoami have the following contents:

#!/bin/bash

# this plugin makes use of the `kubectl config` command in order to output
# information about the current user, based on the currently selected context
kubectl config view --template='{{ range .contexts }}{{ if eq .name "'$(kubectl config current-context)'" }}Current user: {{ printf "%s\n" .context.user }}{{ end }}{{ end }}'

Running the above command gives you an output containing the user for the current context in your KUBECONFIG file:

# make the file executable
sudo chmod +x ./kubectl-whoami

# and move it into your PATH
sudo mv ./kubectl-whoami /usr/local/bin

kubectl whoami
Current user: plugins-user

What's next

Last modified March 03, 2022 at 10:02 AM PST: Use in-page “what's next” list for kubectl (77a598cb33)