kubectl/docs/book/pages/imperative_porcelain/setting_fields.md

{% panel style="success", title="Providing Feedback" %} Provide feedback at the survey {% endpanel %}

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• Imperatively Set fields on Resources {% endpanel %}

Creating Resources

Motivation

Set fields on Resources directly from the command line for the purposes of development or debugging. Not for production Application Management.

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Scale

The Replicas field on a Resource can be set using the kubectl scale command.

{% sample lang="yaml" %}

# Scale a replicaset named 'foo' to 3.
kubectl scale --replicas=3 rs/foo

# Scale a resource identified by type and name specified in "foo.yaml" to 3.
kubectl scale --replicas=3 -f foo.yaml

# If the deployment named mysql's current size is 2, scale mysql to 3.
kubectl scale --current-replicas=2 --replicas=3 deployment/mysql

# Scale multiple replication controllers.
kubectl scale --replicas=5 rc/foo rc/bar rc/baz

# Scale statefulset named 'web' to 3.
kubectl scale --replicas=3 statefulset/web

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{% panel style="info", title="Conditional Scale Update" %} It is possible to conditionally update the replicas if and only if the replicas haven't changed from their last known value using the --current-replicas flag. e.g. kubectl scale --current-replicas=2 --replicas=3 deployment/mysql {% endpanel %}

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Labels

Labels can be set using the kubectl label command. Multiple Resources can be updated in a single command using the -l flag.

{% sample lang="yaml" %}

# Update pod 'foo' with the label 'unhealthy' and the value 'true'.
kubectl label pods foo unhealthy=true

# Update pod 'foo' with the label 'status' and the value 'unhealthy', overwriting any existing value.
kubectl label --overwrite pods foo status=unhealthy

# Update all pods in the namespace
kubectl label pods --all status=unhealthy

# Update a pod identified by the type and name in "pod.json"
kubectl label -f pod.json status=unhealthy

# Update pod 'foo' only if the resource is unchanged from version 1.
kubectl label pods foo status=unhealthy --resource-version=1

# Update pod 'foo' by removing a label named 'bar' if it exists.
# Does not require the --overwrite flag.
kubectl label pods foo bar-

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Annotations

Annotations can be set using the kubectl annotate command.

{% sample lang="yaml" %}

# Update pod 'foo' with the annotation 'description' and the value 'my frontend'.
# If the same annotation is set multiple times, only the last value will be applied
kubectl annotate pods foo description='my frontend'

# Update a pod identified by type and name in "pod.json"
kubectl annotate -f pod.json description='my frontend'

# Update pod 'foo' with the annotation 'description' and the value 'my frontend running nginx', overwriting any
existing value.
kubectl annotate --overwrite pods foo description='my frontend running nginx'

# Update all pods in the namespace
kubectl annotate pods --all description='my frontend running nginx'

# Update pod 'foo' only if the resource is unchanged from version 1.
kubectl annotate pods foo description='my frontend running nginx' --resource-version=1

# Update pod 'foo' by removing an annotation named 'description' if it exists.
# Does not require the --overwrite flag.
kubectl annotate pods foo description-

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Patches

Arbitrary fields can be set using the kubectl patch command.

{% sample lang="yaml" %}

# Partially update a node using a strategic merge patch. Specify the patch as JSON.
kubectl patch node k8s-node-1 -p '{"spec":{"unschedulable":true}}'

# Partially update a node using a strategic merge patch. Specify the patch as YAML.
kubectl patch node k8s-node-1 -p $'spec:\n unschedulable: true'

# Partially update a node identified by the type and name specified in "node.json" using strategic merge patch.
kubectl patch -f node.json -p '{"spec":{"unschedulable":true}}'

# Update a container's image; spec.containers[*].name is required because it's a merge key.
kubectl patch pod valid-pod -p '{"spec":{"containers":[{"name":"kubernetes-serve-hostname","image":"new image"}]}}'

# Update a container's image using a json patch with positional arrays.
kubectl patch pod valid-pod --type='json' -p='[{"op": "replace", "path": "/spec/containers/0/image", "value":"newimage"}]'

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