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TL;DR
  • Imperatively Set fields on Resources

Creating Resources

Motivation

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

Scale

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

# 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

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

Labels

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

# 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-

Annotations

Annotations can be set using the kubectl annotate command.

# 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-

Patches

Arbitrary fields can be set using the kubectl patch command.

# 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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