# Extend the Kubernetes API with CustomResourceDefinitions

Extend the Kubernetes API with CustomResourceDefinitionsThis page shows how to install a custom resource into the Kubernetes API by creating a CustomResourceDefinition.Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:iximiuz LabsKillercodaKodeKloudPlay with KubernetesYour Kubernetes server must be at or later than version 1.16.To check the version, enter kubectl version.If you are using an older version of Kubernetes that is still supported, switch to the documentation for that version to see advice that is relevant for your cluster.Create a CustomResourceDefinitionWhen you create a new CustomResourceDefinition (CRD), the Kubernetes API Server creates a new RESTful resource path for each version you specify. The custom resource created from a CRD object can be either namespaced or cluster-scoped, as specified in the CRD's spec.scope field. As with existing built-in objects, deleting a namespace deletes all custom objects in that namespace. CustomResourceDefinitions themselves are non-namespaced and are available to all namespaces.For example, if you save the following CustomResourceDefinition to resourcedefinition.yaml:apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: # name must match the spec fields below, and be in the form: <plural>.<group> name: crontabs.stable.example.com spec: # group name to use for REST API: /apis/<group>/<version> group: stable.example.com # list of versions supported by this CustomResourceDefinition versions: - name: v1 # Each version can be enabled/disabled by Served flag. served: true # One and only one version must be marked as the storage version. storage: true schema: openAPIV3Schema: type: object properties: spec: type: object properties: cronSpec: type: string image: type: string replicas: type: integer # either Namespaced or Cluster scope: Namespaced names: # plural name to be used in the URL: /apis/<group>/<version>/<plural> plural: crontabs # singular name to be used as an alias on the CLI and for display singular: crontab # kind is normally the CamelCased singular type. Your resource manifests use this. kind: CronTab # shortNames allow shorter string to match your resource on the CLI shortNames: - ct and create it:kubectl apply -f resourcedefinition.yaml Then a new namespaced RESTful API endpoint is created at:/apis/stable.example.com/v1/namespaces/*/crontabs/... This endpoint URL can then be used to create and manage custom objects. The kind of these objects will be CronTab from the spec of the CustomResourceDefinition object you created above.It might take a few seconds for the endpoint to be created. You can watch the Established condition of your CustomResourceDefinition to be true or watch the discovery information of the API server for your resource to show up.Create custom objectsAfter the CustomResourceDefinition object has been created, you can create custom objects. Custom objects can contain custom fields. These fields can contain arbitrary JSON. In the following example, the cronSpec and image custom fields are set in a custom object of kind CronTab. The kind CronTab comes from the spec of the CustomResourceDefinition object you created above.If you save the following YAML to my-crontab.yaml:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: cronSpec: "* * * * */5" image: my-awesome-cron-image and create it:kubectl apply -f my-crontab.yaml You can then manage your CronTab objects using kubectl. For example:kubectl get crontab Should print a list like this:NAME AGE my-new-cron-object 6s Resource names are not case-sensitive when using kubectl, and you can use either the singular or plural forms defined in the CRD, as well as any short names.You can also view the raw YAML data:kubectl get ct -o yaml You should see that it contains the custom cronSpec and image fields from the YAML you used to create it:apiVersion: v1 items: - apiVersion: stable.example.com/v1 kind: CronTab metadata: annotations: kubectl.kubernetes.io/last-applied-configuration: | {"apiVersion":"stable.example.com/v1","kind":"CronTab","metadata":{"annotations":{},"name":"my-new-cron-object","namespace":"default"},"spec":{"cronSpec":"* * * * */5","image":"my-awesome-cron-image"}} creationTimestamp: "2021-06-20T07:35:27Z" generation: 1 name: my-new-cron-object namespace: default resourceVersion: "1326" uid: 9aab1d66-628e-41bb-a422-57b8b3b1f5a9 spec: cronSpec: '* * * * */5' image: my-awesome-cron-image kind: List metadata: resourceVersion: "" selfLink: "" Delete a CustomResourceDefinitionWhen you delete a CustomResourceDefinition, the server will uninstall the RESTful API endpoint and delete all custom objects stored in it.kubectl delete -f resourcedefinition.yaml kubectl get crontabs Error from server (NotFound): Unable to list {"stable.example.com" "v1" "crontabs"}: the server could not find the requested resource (get crontabs.stable.example.com) If you later recreate the same CustomResourceDefinition, it will start out empty.Specifying a structural schemaCustomResources store structured data in custom fields (alongside the built-in fields apiVersion, kind and metadata, which the API server validates implicitly). With OpenAPI v3.0 validation a schema can be specified, which is validated during creation and updates, compare below for details and limits of such a schema.With apiextensions.k8s.io/v1 the definition of a structural schema is mandatory for CustomResourceDefinitions. In the beta version of CustomResourceDefinition, the structural schema was optional.A structural schema is an OpenAPI v3.0 validation schema which:specifies a non-empty type (via type in OpenAPI) for the root, for each specified field of an object node (via properties or additionalProperties in OpenAPI) and for each item in an array node (via items in OpenAPI), with the exception of:a node with x-kubernetes-int-or-string: truea node with x-kubernetes-preserve-unknown-fields: truefor each field in an object and each item in an array which is specified within any of allOf, anyOf, oneOf or not, the schema also specifies the field/item outside of those logical junctors (compare example 1 and 2).does not set description, type, default, additionalProperties, nullable within an allOf, anyOf, oneOf or not, with the exception of the two pattern for x-kubernetes-int-or-string: true (see below).if metadata is specified, then only restrictions on metadata.name and metadata.generateName are allowed.Non-structural example 1:allOf: - properties: foo: # ... conflicts with rule 2. The following would be correct:properties: foo: # ... allOf: - properties: foo: # ... Non-structural example 2:allOf: - items: properties: foo: # ... conflicts with rule 2. The following would be correct:items: properties: foo: # ... allOf: - items: properties: foo: # ... Non-structural example 3:properties: foo: pattern: "abc" metadata: type: object properties: name: type: string pattern: "^a" finalizers: type: array items: type: string pattern: "my-finalizer" anyOf: - properties: bar: type: integer minimum: 42 required: ["bar"] description: "foo bar object" is not a structural schema because of the following violations:the type at the root is missing (rule 1).the type of foo is missing (rule 1).bar inside of anyOf is not specified outside (rule 2).bar's type is within anyOf (rule 3).the description is set within anyOf (rule 3).metadata.finalizers might not be restricted (rule 4).In contrast, the following, corresponding schema is structural:type: object description: "foo bar object" properties: foo: type: string pattern: "abc" bar: type: integer metadata: type: object properties: name: type: string pattern: "^a" anyOf: - properties: bar: minimum: 42 required: ["bar"] Violations of the structural schema rules are reported in the NonStructural condition in the CustomResourceDefinition.Field pruningCustomResourceDefinitions store validated resource data in the cluster's persistence store, etcd. As with native Kubernetes resources such as ConfigMap, if you specify a field that the API server does not recognize, the unknown field is pruned (removed) before being persisted.CRDs converted from apiextensions.k8s.io/v1beta1 to apiextensions.k8s.io/v1 might lack structural schemas, and spec.preserveUnknownFields might be true.For legacy CustomResourceDefinition objects created as apiextensions.k8s.io/v1beta1 with spec.preserveUnknownFields set to true, the following is also true:Pruning is not enabled.You can store arbitrary data.For compatibility with apiextensions.k8s.io/v1, update your custom resource definitions to:Use a structural OpenAPI schema.Set spec.preserveUnknownFields to false.If you save the following YAML to my-crontab.yaml:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: cronSpec: "* * * * */5" image: my-awesome-cron-image someRandomField: 42 and create it:kubectl create --validate=false -f my-crontab.yaml -o yaml Your output is similar to:apiVersion: stable.example.com/v1 kind: CronTab metadata: creationTimestamp: 2017-05-31T12:56:35Z generation: 1 name: my-new-cron-object namespace: default resourceVersion: "285" uid: 9423255b-4600-11e7-af6a-28d2447dc82b spec: cronSpec: '* * * * */5' image: my-awesome-cron-image Notice that the field someRandomField was pruned.This example turned off client-side validation to demonstrate the API server's behavior, by adding the --validate=false command line option. Because the OpenAPI validation schemas are also published to clients, kubectl also checks for unknown fields and rejects those objects well before they would be sent to the API server.Controlling pruningBy default, all unspecified fields for a custom resource, across all versions, are pruned. It is possible though to opt-out of that for specific sub-trees of fields by adding x-kubernetes-preserve-unknown-fields: true in the structural OpenAPI v3 validation schema.For example:type: object properties: json: x-kubernetes-preserve-unknown-fields: true The field json can store any JSON value, without anything being pruned.You can also partially specify the permitted JSON; for example:type: object properties: json: x-kubernetes-preserve-unknown-fields: true type: object description: this is arbitrary JSON With this, only object type values are allowed.Pruning is enabled again for each specified property (or additionalProperties):type: object properties: json: x-kubernetes-preserve-unknown-fields: true type: object properties: spec: type: object properties: foo: type: string bar: type: string With this, the value:json: spec: foo: abc bar: def something: x status: something: x is pruned to:json: spec: foo: abc bar: def status: something: x This means that the something field in the specified spec object is pruned, but everything outside is not.IntOrStringNodes in a schema with x-kubernetes-int-or-string: true are excluded from rule 1, such that the following is structural:type: object properties: foo: x-kubernetes-int-or-string: true Also those nodes are partially excluded from rule 3 in the sense that the following two patterns are allowed (exactly those, without variations in order to additional fields):x-kubernetes-int-or-string: true anyOf: - type: integer - type: string ... andx-kubernetes-int-or-string: true allOf: - anyOf: - type: integer - type: string - # ... zero or more ... With one of those specification, both an integer and a string validate.In Validation Schema Publishing, x-kubernetes-int-or-string: true is unfolded to one of the two patterns shown above.RawExtensionRawExtensions (as in runtime.RawExtension) holds complete Kubernetes objects, i.e. with apiVersion and kind fields.It is possible to specify those embedded objects (both completely without constraints or partially specified) by setting x-kubernetes-embedded-resource: true. For example:type: object properties: foo: x-kubernetes-embedded-resource: true x-kubernetes-preserve-unknown-fields: true Here, the field foo holds a complete object, e.g.:foo: apiVersion: v1 kind: Pod spec: # ... Because x-kubernetes-preserve-unknown-fields: true is specified alongside, nothing is pruned. The use of x-kubernetes-preserve-unknown-fields: true is optional though.With x-kubernetes-embedded-resource: true, the apiVersion, kind and metadata are implicitly specified and validated.Serving multiple versions of a CRDSee Custom resource definition versioning for more information about serving multiple versions of your CustomResourceDefinition and migrating your objects from one version to another.Advanced topicsFinalizersFinalizers allow controllers to implement asynchronous pre-delete hooks. Custom objects support finalizers similar to built-in objects.You can add a finalizer to a custom object like this:apiVersion: "stable.example.com/v1" kind: CronTab metadata: finalizers: - stable.example.com/finalizer Identifiers of custom finalizers consist of a domain name, a forward slash and the name of the finalizer. Any controller can add a finalizer to any object's list of finalizers.The first delete request on an object with finalizers sets a value for the metadata.deletionTimestamp field but does not delete it. Once this value is set, entries in the finalizers list can only be removed. While any finalizers remain it is also impossible to force the deletion of an object.When the metadata.deletionTimestamp field is set, controllers watching the object execute any finalizers they handle and remove the finalizer from the list after they are done. It is the responsibility of each controller to remove its finalizer from the list.The value of metadata.deletionGracePeriodSeconds controls the interval between polling updates.Once the list of finalizers is empty, meaning all finalizers have been executed, the resource is deleted by Kubernetes.ValidationCustom resources are validated via OpenAPI v3.0 schemas, by x-kubernetes-validations when the Validation Rules feature is enabled, and you can add additional validation using admission webhooks.Additionally, the following restrictions are applied to the schema:These fields cannot be set:definitions,dependencies,deprecated,discriminator,id,patternProperties,readOnly,writeOnly,xml,$ref.The field uniqueItems cannot be set to true.The field additionalProperties cannot be set to false.The field additionalProperties is mutually exclusive with properties.The x-kubernetes-validations extension can be used to validate custom resources using Common Expression Language (CEL) expressions when the Validation rules feature is enabled and the CustomResourceDefinition schema is a structural schema.Refer to the structural schemas section for other restrictions and CustomResourceDefinition features.The schema is defined in the CustomResourceDefinition. In the following example, the CustomResourceDefinition applies the following validations on the custom object:spec.cronSpec must be a string and must be of the form described by the regular expression.spec.replicas must be an integer and must have a minimum value of 1 and a maximum value of 10.Save the CustomResourceDefinition to resourcedefinition.yaml:apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: name: crontabs.stable.example.com spec: group: stable.example.com versions: - name: v1 served: true storage: true schema: # openAPIV3Schema is the schema for validating custom objects. openAPIV3Schema: type: object properties: spec: type: object properties: cronSpec: type: string pattern: '^(\d+|\*)(/\d+)?(\s+(\d+|\*)(/\d+)?){4}$' image: type: string replicas: type: integer minimum: 1 maximum: 10 scope: Namespaced names: plural: crontabs singular: crontab kind: CronTab shortNames: - ct and create it:kubectl apply -f resourcedefinition.yaml A request to create a custom object of kind CronTab is rejected if there are invalid values in its fields. In the following example, the custom object contains fields with invalid values:spec.cronSpec does not match the regular expression.spec.replicas is greater than 10.If you save the following YAML to my-crontab.yaml:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: cronSpec: "* * * *" image: my-awesome-cron-image replicas: 15 and attempt to create it:kubectl apply -f my-crontab.yaml then you get an error:The CronTab "my-new-cron-object" is invalid: []: Invalid value: map[string]interface {}{"apiVersion":"stable.example.com/v1", "kind":"CronTab", "metadata":map[string]interface {}{"name":"my-new-cron-object", "namespace":"default", "deletionTimestamp":interface {}(nil), "deletionGracePeriodSeconds":(*int64)(nil), "creationTimestamp":"2017-09-05T05:20:07Z", "uid":"e14d79e7-91f9-11e7-a598-f0761cb232d1", "clusterName":""}, "spec":map[string]interface {}{"cronSpec":"* * * *", "image":"my-awesome-cron-image", "replicas":15}}: validation failure list: spec.cronSpec in body should match '^(\d+|\*)(/\d+)?(\s+(\d+|\*)(/\d+)?){4}$' spec.replicas in body should be less than or equal to 10 If the fields contain valid values, the object creation request is accepted.Save the following YAML to my-crontab.yaml:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: cronSpec: "* * * * */5" image: my-awesome-cron-image replicas: 5 And create it:kubectl apply -f my-crontab.yaml crontab "my-new-cron-object" created Validation ratchetingFEATURE STATE: Kubernetes v1.33 [stable] (enabled by default: true)If you are using a version of Kubernetes older than v1.30, you need to explicitly enable the CRDValidationRatcheting feature gate to use this behavior, which then applies to all CustomResourceDefinitions in your cluster.Provided you enabled the feature gate, Kubernetes implements validation ratcheting for CustomResourceDefinitions. The API server is willing to accept updates to resources that are not valid after the update, provided that each part of the resource that failed to validate was not changed by the update operation. In other words, any invalid part of the resource that remains invalid must have already been wrong. You cannot use this mechanism to update a valid resource so that it becomes invalid.This feature allows authors of CRDs to confidently add new validations to the OpenAPIV3 schema under certain conditions. Users can update to the new schema safely without bumping the version of the object or breaking workflows.While most validations placed in the OpenAPIV3 schema of a CRD support ratcheting, there are a few exceptions. The following OpenAPIV3 schema validations are not supported by ratcheting under the implementation in Kubernetes 1.34 and if violated will continue to throw an error as normally:QuantorsallOfoneOfanyOfnotany validations in a descendent of one of these fieldsx-kubernetes-validations For Kubernetes 1.28, CRD validation rules are ignored by ratcheting. Starting with Alpha 2 in Kubernetes 1.29, x-kubernetes-validations are ratcheted only if they do not refer to oldSelf.Transition Rules are never ratcheted: only errors raised by rules that do not use oldSelf will be automatically ratcheted if their values are unchanged.To write custom ratcheting logic for CEL expressions, check out optionalOldSelf.x-kubernetes-list-type Errors arising from changing the list type of a subschema will not be ratcheted. For example adding set onto a list with duplicates will always result in an error.x-kubernetes-list-map-keys Errors arising from changing the map keys of a list schema will not be ratcheted.required Errors arising from changing the list of required fields will not be ratcheted.properties Adding/removing/modifying the names of properties is not ratcheted, but changes to validations in each properties' schemas and subschemas may be ratcheted if the name of the property stays the same.additionalProperties To remove a previously specified additionalProperties validation will not be ratcheted.metadata Errors that come from Kubernetes' built-in validation of an object's metadata are not ratcheted (such as object name, or characters in a label value). If you specify your own additional rules for the metadata of a custom resource, that additional validation will be ratcheted.Validation rulesFEATURE STATE: Kubernetes v1.29 [stable]Validation rules use the Common Expression Language (CEL) to validate custom resource values. Validation rules are included in CustomResourceDefinition schemas using the x-kubernetes-validations extension.The Rule is scoped to the location of the x-kubernetes-validations extension in the schema. And self variable in the CEL expression is bound to the scoped value.All validation rules are scoped to the current object: no cross-object or stateful validation rules are supported.For example: # ... openAPIV3Schema: type: object properties: spec: type: object x-kubernetes-validations: - rule: "self.minReplicas <= self.replicas" message: "replicas should be greater than or equal to minReplicas." - rule: "self.replicas <= self.maxReplicas" message: "replicas should be smaller than or equal to maxReplicas." properties: # ... minReplicas: type: integer replicas: type: integer maxReplicas: type: integer required: - minReplicas - replicas - maxReplicas will reject a request to create this custom resource:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: minReplicas: 0 replicas: 20 maxReplicas: 10 with the response:The CronTab "my-new-cron-object" is invalid: * spec: Invalid value: map[string]interface {}{"maxReplicas":10, "minReplicas":0, "replicas":20}: replicas should be smaller than or equal to maxReplicas. x-kubernetes-validations could have multiple rules. The rule under x-kubernetes-validations represents the expression which will be evaluated by CEL. The message represents the message displayed when validation fails. If message is unset, the above response would be:The CronTab "my-new-cron-object" is invalid: * spec: Invalid value: map[string]interface {}{"maxReplicas":10, "minReplicas":0, "replicas":20}: failed rule: self.replicas <= self.maxReplicas Note:You can quickly test CEL expressions in CEL Playground.Validation rules are compiled when CRDs are created/updated. The request of CRDs create/update will fail if compilation of validation rules fail. Compilation process includes type checking as well.The compilation failure:no_matching_overload: this function has no overload for the types of the arguments.For example, a rule like self == true against a field of integer type will get error:Invalid value: apiextensions.ValidationRule{Rule:"self == true", Message:""}: compilation failed: ERROR: \<input>:1:6: found no matching overload for '_==_' applied to '(int, bool)' no_such_field: does not contain the desired field.For example, a rule like self.nonExistingField > 0 against a non-existing field will return the following error:Invalid value: apiextensions.ValidationRule{Rule:"self.nonExistingField > 0", Message:""}: compilation failed: ERROR: \<input>:1:5: undefined field 'nonExistingField' invalid argument: invalid argument to macros.For example, a rule like has(self) will return error:Invalid value: apiextensions.ValidationRule{Rule:"has(self)", Message:""}: compilation failed: ERROR: <input>:1:4: invalid argument to has() macro Validation Rules Examples:RulePurposeself.minReplicas <= self.replicas && self.replicas <= self.maxReplicasValidate that the three fields defining replicas are ordered appropriately'Available' in self.stateCountsValidate that an entry with the 'Available' key exists in a map(size(self.list1) == 0) != (size(self.list2) == 0)Validate that one of two lists is non-empty, but not both!('MY_KEY' in self.map1) || self['MY_KEY'].matches('^[a-zA-Z]*$')Validate the value of a map for a specific key, if it is in the mapself.envars.filter(e, e.name == 'MY_ENV').all(e, e.value.matches('^[a-zA-Z]*$')Validate the 'value' field of a listMap entry where key field 'name' is 'MY_ENV'has(self.expired) && self.created + self.ttl < self.expiredValidate that 'expired' date is after a 'create' date plus a 'ttl' durationself.health.startsWith('ok')Validate a 'health' string field has the prefix 'ok'self.widgets.exists(w, w.key == 'x' && w.foo < 10)Validate that the 'foo' property of a listMap item with a key 'x' is less than 10type(self) == string ? self == '100%' : self == 1000Validate an int-or-string field for both the int and string casesself.metadata.name.startsWith(self.prefix)Validate that an object's name has the prefix of another field valueself.set1.all(e, !(e in self.set2))Validate that two listSets are disjointsize(self.names) == size(self.details) && self.names.all(n, n in self.details)Validate the 'details' map is keyed by the items in the 'names' listSetsize(self.clusters.filter(c, c.name == self.primary)) == 1Validate that the 'primary' property has one and only one occurrence in the 'clusters' listMapXref: Supported evaluation on CELIf the Rule is scoped to the root of a resource, it may make field selection into any fields declared in the OpenAPIv3 schema of the CRD as well as apiVersion, kind, metadata.name and metadata.generateName. This includes selection of fields in both the spec and status in the same expression: # ... openAPIV3Schema: type: object x-kubernetes-validations: - rule: "self.status.availableReplicas >= self.spec.minReplicas" properties: spec: type: object properties: minReplicas: type: integer # ... status: type: object properties: availableReplicas: type: integer If the Rule is scoped to an object with properties, the accessible properties of the object are field selectable via self.field and field presence can be checked via has(self.field). Null valued fields are treated as absent fields in CEL expressions. # ... openAPIV3Schema: type: object properties: spec: type: object x-kubernetes-validations: - rule: "has(self.foo)" properties: # ... foo: type: integer If the Rule is scoped to an object with additionalProperties (i.e. a map) the value of the map are accessible via self[mapKey], map containment can be checked via mapKey in self and all entries of the map are accessible via CEL macros and functions such as self.all(...). # ... openAPIV3Schema: type: object properties: spec: type: object x-kubernetes-validations: - rule: "self['xyz'].foo > 0" additionalProperties: # ... type: object properties: foo: type: integer If the Rule is scoped to an array, the elements of the array are accessible via self[i] and also by macros and functions. # ... openAPIV3Schema: type: object properties: # ... foo: type: array x-kubernetes-validations: - rule: "size(self) == 1" items: type: string If the Rule is scoped to a scalar, self is bound to the scalar value. # ... openAPIV3Schema: type: object properties: spec: type: object properties: # ... foo: type: integer x-kubernetes-validations: - rule: "self > 0" Examples:type of the field rule scoped toRule exampleroot objectself.status.actual <= self.spec.maxDesiredmap of objectsself.components['Widget'].priority < 10list of integersself.values.all(value, value >= 0 && value < 100)stringself.startsWith('kube')The apiVersion, kind, metadata.name and metadata.generateName are always accessible from the root of the object and from any x-kubernetes-embedded-resource annotated objects. No other metadata properties are accessible.Unknown data preserved in custom resources via x-kubernetes-preserve-unknown-fields is not accessible in CEL expressions. This includes:Unknown field values that are preserved by object schemas with x-kubernetes-preserve-unknown-fields.Object properties where the property schema is of an "unknown type". An "unknown type" is recursively defined as:A schema with no type and x-kubernetes-preserve-unknown-fields set to trueAn array where the items schema is of an "unknown type"An object where the additionalProperties schema is of an "unknown type"Only property names of the form [a-zA-Z_.-/][a-zA-Z0-9_.-/]* are accessible. Accessible property names are escaped according to the following rules when accessed in the expression:escape sequenceproperty name equivalent__underscores______dot__.__dash__-__slash__/__{keyword}__CEL RESERVED keywordNote: CEL RESERVED keyword needs to match the exact property name to be escaped (e.g. int in the word sprint would not be escaped).Examples on escaping:property namerule with escaped property namenamespaceself.__namespace__ > 0x-propself.x__dash__prop > 0redact__dself.redact__underscores__d > 0stringself.startsWith('kube')Equality on arrays with x-kubernetes-list-type of set or map ignores element order, i.e., [1, 2] == [2, 1]. Concatenation on arrays with x-kubernetes-list-type use the semantics of the list type:set: X + Y performs a union where the array positions of all elements in X are preserved and non-intersecting elements in Y are appended, retaining their partial order.map: X + Y performs a merge where the array positions of all keys in X are preserved but the values are overwritten by values in Y when the key sets of X and Y intersect. Elements in Y with non-intersecting keys are appended, retaining their partial order.Here is the declarations type mapping between OpenAPIv3 and CEL type:OpenAPIv3 typeCEL type'object' with Propertiesobject / "message type"'object' with AdditionalPropertiesmap'object' with x-kubernetes-embedded-typeobject / "message type", 'apiVersion', 'kind', 'metadata.name' and 'metadata.generateName' are implicitly included in schema'object' with x-kubernetes-preserve-unknown-fieldsobject / "message type", unknown fields are NOT accessible in CEL expressionx-kubernetes-int-or-stringdynamic object that is either an int or a string, type(value) can be used to check the type'arraylist'array' with x-kubernetes-list-type=maplist with map based Equality & unique key guarantees'array' with x-kubernetes-list-type=setlist with set based Equality & unique entry guarantees'boolean'boolean'number' (all formats)double'integer' (all formats)int (64)'null'null_type'string'string'string' with format=byte (base64 encoded)bytes'string' with format=datetimestamp (google.protobuf.Timestamp)'string' with format=datetimetimestamp (google.protobuf.Timestamp)'string' with format=durationduration (google.protobuf.Duration)xref: CEL types, OpenAPI types, Kubernetes Structural Schemas.The messageExpression fieldSimilar to the message field, which defines the string reported for a validation rule failure, messageExpression allows you to use a CEL expression to construct the message string. This allows you to insert more descriptive information into the validation failure message. messageExpression must evaluate a string and may use the same variables that are available to the rule field. For example:x-kubernetes-validations: - rule: "self.x <= self.maxLimit" messageExpression: '"x exceeded max limit of " + string(self.maxLimit)' Keep in mind that CEL string concatenation (+ operator) does not auto-cast to string. If you have a non-string scalar, use the string(<value>) function to cast the scalar to a string like shown in the above example.messageExpression must evaluate to a string, and this is checked while the CRD is being written. Note that it is possible to set message and messageExpression on the same rule, and if both are present, messageExpression will be used. However, if messageExpression evaluates to an error, the string defined in message will be used instead, and the messageExpression error will be logged. This fallback will also occur if the CEL expression defined in messageExpression generates an empty string, or a string containing line breaks.If one of the above conditions are met and no message has been set, then the default validation failure message will be used instead.messageExpression is a CEL expression, so the restrictions listed in Resource use by validation functions apply. If evaluation halts due to resource constraints during messageExpression execution, then no further validation rules will be executed.Setting messageExpression is optional.The message fieldIf you want to set a static message, you can supply message rather than messageExpression. The value of message is used as an opaque error string if validation fails.Setting message is optional.The reason fieldYou can add a machine-readable validation failure reason within a validation, to be returned whenever a request fails this validation rule.For example:x-kubernetes-validations: - rule: "self.x <= self.maxLimit" reason: "FieldValueInvalid" The HTTP status code returned to the caller will match the reason of the first failed validation rule. The currently supported reasons are: "FieldValueInvalid", "FieldValueForbidden", "FieldValueRequired", "FieldValueDuplicate". If not set or unknown reasons, default to use "FieldValueInvalid".Setting reason is optional.The fieldPath fieldYou can specify the field path returned when the validation fails.For example:x-kubernetes-validations: - rule: "self.foo.test.x <= self.maxLimit" fieldPath: ".foo.test.x" In the example above, the validation checks the value of field x should be less than the value of maxLimit. If no fieldPath specified, when validation fails, the fieldPath would be default to wherever self scoped. With fieldPath specified, the returned error will have fieldPath properly refer to the location of field x.The fieldPath value must be a relative JSON path that is scoped to the location of this x-kubernetes-validations extension in the schema. Additionally, it should refer to an existing field within the schema. For example when validation checks if a specific attribute foo under a map testMap, you could set fieldPath to ".testMap.foo" or .testMap['foo']'. If the validation requires checking for unique attributes in two lists, the fieldPath can be set to either of the lists. For example, it can be set to .testList1 or .testList2. It supports child operation to refer to an existing field currently. Refer to JSONPath support in Kubernetes for more info. The fieldPath field does not support indexing arrays numerically.Setting fieldPath is optional.The optionalOldSelf fieldFEATURE STATE: Kubernetes v1.33 [stable] (enabled by default: true)If your cluster does not have CRD validation ratcheting enabled, the CustomResourceDefinition API doesn't include this field, and trying to set it may result in an error.The optionalOldSelf field is a boolean field that alters the behavior of Transition Rules described below. Normally, a transition rule will not evaluate if oldSelf cannot be determined: during object creation or when a new value is introduced in an update.If optionalOldSelf is set to true, then transition rules will always be evaluated and the type of oldSelf be changed to a CEL Optional type.optionalOldSelf is useful in cases where schema authors would like a more control tool than provided by the default equality based behavior of to introduce newer, usually stricter constraints on new values, while still allowing old values to be "grandfathered" or ratcheted using the older validation.Example Usage:CELDescriptionself.foo == "foo" || (oldSelf.hasValue() && oldSelf.value().foo != "foo")Ratcheted rule. Once a value is set to "foo", it must stay foo. But if it existed before the "foo" constraint was introduced, it may use any value[oldSelf.orValue(""), self].all(x, ["OldCase1", "OldCase2"].exists(case, x == case)) || ["NewCase1", "NewCase2"].exists(case, self == case) || ["NewCase"].has(self)"Ratcheted validation for removed enum cases if oldSelf used them"oldSelf.optMap(o, o.size()).orValue(0) < 4 || self.size() >= 4Ratcheted validation of newly increased minimum map or list sizeValidation functionsFunctions available include:CEL standard functions, defined in the list of standard definitionsCEL standard macrosCEL extended string function libraryKubernetes CEL extension libraryTransition rulesA rule that contains an expression referencing the identifier oldSelf is implicitly considered a transition rule. Transition rules allow schema authors to prevent certain transitions between two otherwise valid states. For example:type: string enum: ["low", "medium", "high"] x-kubernetes-validations: - rule: "!(self == 'high' && oldSelf == 'low') && !(self == 'low' && oldSelf == 'high')" message: cannot transition directly between 'low' and 'high' Unlike other rules, transition rules apply only to operations meeting the following criteria:The operation updates an existing object. Transition rules never apply to create operations.Both an old and a new value exist. It remains possible to check if a value has been added or removed by placing a transition rule on the parent node. Transition rules are never applied to custom resource creation. When placed on an optional field, a transition rule will not apply to update operations that set or unset the field.The path to the schema node being validated by a transition rule must resolve to a node that is comparable between the old object and the new object. For example, list items and their descendants (spec.foo[10].bar) can't necessarily be correlated between an existing object and a later update to the same object.Errors will be generated on CRD writes if a schema node contains a transition rule that can never be applied, e.g. "oldSelf cannot be used on the uncorrelatable portion of the schema within path".Transition rules are only allowed on correlatable portions of a schema. A portion of the schema is correlatable if all array parent schemas are of type x-kubernetes-list-type=map; any setor atomicarray parent schemas make it impossible to unambiguously correlate a self with oldSelf.Here are some examples for transition rules:Transition rules examplesUse CaseRuleImmutabilityself.foo == oldSelf.fooPrevent modification/removal once assignedoldSelf != 'bar' || self == 'bar' or !has(oldSelf.field) || has(self.field)Append-only setself.all(element, element in oldSelf)If previous value was X, new value can only be A or B, not Y or ZoldSelf != 'X' || self in ['A', 'B']Monotonic (non-decreasing) countersself >= oldSelfResource use by validation functionsWhen you create or update a CustomResourceDefinition that uses validation rules, the API server checks the likely impact of running those validation rules. If a rule is estimated to be prohibitively expensive to execute, the API server rejects the create or update operation, and returns an error message. A similar system is used at runtime that observes the actions the interpreter takes. If the interpreter executes too many instructions, execution of the rule will be halted, and an error will result. Each CustomResourceDefinition is also allowed a certain amount of resources to finish executing all of its validation rules. If the sum total of its rules are estimated at creation time to go over that limit, then a validation error will also occur.You are unlikely to encounter issues with the resource budget for validation if you only specify rules that always take the same amount of time regardless of how large their input is. For example, a rule that asserts that self.foo == 1 does not by itself have any risk of rejection on validation resource budget groups. But if foo is a string and you define a validation rule self.foo.contains("someString"), that rule takes longer to execute depending on how long foo is. Another example would be if foo were an array, and you specified a validation rule self.foo.all(x, x > 5). The cost system always assumes the worst-case scenario if a limit on the length of foo is not given, and this will happen for anything that can be iterated over (lists, maps, etc.).Because of this, it is considered best practice to put a limit via maxItems, maxProperties, and maxLength for anything that will be processed in a validation rule in order to prevent validation errors during cost estimation. For example, given this schema with one rule:openAPIV3Schema: type: object properties: foo: type: array items: type: string x-kubernetes-validations: - rule: "self.all(x, x.contains('a string'))" then the API server rejects this rule on validation budget grounds with error:spec.validation.openAPIV3Schema.properties[spec].properties[foo].x-kubernetes-validations[0].rule: Forbidden: CEL rule exceeded budget by more than 100x (try simplifying the rule, or adding maxItems, maxProperties, and maxLength where arrays, maps, and strings are used) The rejection happens because self.all implies calling contains() on every string in foo, which in turn will check the given string to see if it contains 'a string'. Without limits, this is a very expensive rule.If you do not specify any validation limit, the estimated cost of this rule will exceed the per-rule cost limit. But if you add limits in the appropriate places, the rule will be allowed:openAPIV3Schema: type: object properties: foo: type: array maxItems: 25 items: type: string maxLength: 10 x-kubernetes-validations: - rule: "self.all(x, x.contains('a string'))" The cost estimation system takes into account how many times the rule will be executed in addition to the estimated cost of the rule itself. For instance, the following rule will have the same estimated cost as the previous example (despite the rule now being defined on the individual array items):openAPIV3Schema: type: object properties: foo: type: array maxItems: 25 items: type: string x-kubernetes-validations: - rule: "self.contains('a string'))" maxLength: 10 If a list inside of a list has a validation rule that uses self.all, that is significantly more expensive than a non-nested list with the same rule. A rule that would have been allowed on a non-nested list might need lower limits set on both nested lists in order to be allowed. For example, even without having limits set, the following rule is allowed:openAPIV3Schema: type: object properties: foo: type: array items: type: integer x-kubernetes-validations: - rule: "self.all(x, x == 5)" But the same rule on the following schema (with a nested array added) produces a validation error:openAPIV3Schema: type: object properties: foo: type: array items: type: array items: type: integer x-kubernetes-validations: - rule: "self.all(x, x == 5)" This is because each item of foo is itself an array, and each subarray in turn calls self.all. Avoid nested lists and maps if possible where validation rules are used.DefaultingNote:To use defaulting, your CustomResourceDefinition must use API version apiextensions.k8s.io/v1.Defaulting allows to specify default values in the OpenAPI v3 validation schema:apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: name: crontabs.stable.example.com spec: group: stable.example.com versions: - name: v1 served: true storage: true schema: # openAPIV3Schema is the schema for validating custom objects. openAPIV3Schema: type: object properties: spec: type: object properties: cronSpec: type: string pattern: '^(\d+|\*)(/\d+)?(\s+(\d+|\*)(/\d+)?){4}$' default: "5 0 * * *" image: type: string replicas: type: integer minimum: 1 maximum: 10 default: 1 scope: Namespaced names: plural: crontabs singular: crontab kind: CronTab shortNames: - ct With this both cronSpec and replicas are defaulted:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: image: my-awesome-cron-image leads toapiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: cronSpec: "5 0 * * *" image: my-awesome-cron-image replicas: 1 Defaulting happens on the objectin the request to the API server using the request version defaults,when reading from etcd using the storage version defaults,after mutating admission plugins with non-empty patches using the admission webhook object version defaults.Defaults applied when reading data from etcd are not automatically written back to etcd. An update request via the API is required to persist those defaults back into etcd.Default values for non-leaf fields must be pruned (with the exception of defaults for metadata fields) and must validate against a provided schema. For example in the above example, a default of {"replicas": "foo", "badger": 1} for the spec field would be invalid, because badger is an unknown field, and replicas is not a string.Default values for metadata fields of x-kubernetes-embedded-resources: true nodes (or parts of a default value covering metadata) are not pruned during CustomResourceDefinition creation, but through the pruning step during handling of requests.Defaulting and NullableNull values for fields that either don't specify the nullable flag, or give it a false value, will be pruned before defaulting happens. If a default is present, it will be applied. When nullable is true, null values will be conserved and won't be defaulted.For example, given the OpenAPI schema below:type: object properties: spec: type: object properties: foo: type: string nullable: false default: "default" bar: type: string nullable: true baz: type: string creating an object with null values for foo and bar and bazspec: foo: null bar: null baz: null leads tospec: foo: "default" bar: null with foo pruned and defaulted because the field is non-nullable, bar maintaining the null value due to nullable: true, and baz pruned because the field is non-nullable and has no default.Publish Validation Schema in OpenAPICustomResourceDefinition OpenAPI v3 validation schemas which are structural and enable pruning are published as OpenAPI v3 and OpenAPI v2 from Kubernetes API server. It is recommended to use the OpenAPI v3 document as it is a lossless representation of the CustomResourceDefinition OpenAPI v3 validation schema while OpenAPI v2 represents a lossy conversion.The kubectl command-line tool consumes the published schema to perform client-side validation (kubectl create and kubectl apply), schema explanation (kubectl explain) on custom resources. The published schema can be consumed for other purposes as well, like client generation or documentation.Compatibility with OpenAPI V2For compatibility with OpenAPI V2, the OpenAPI v3 validation schema performs a lossy conversion to the OpenAPI v2 schema. The schema show up in definitions and paths fields in the OpenAPI v2 spec.The following modifications are applied during the conversion to keep backwards compatibility with kubectl in previous 1.13 version. These modifications prevent kubectl from being over-strict and rejecting valid OpenAPI schemas that it doesn't understand. The conversion won't modify the validation schema defined in CRD, and therefore won't affect validation in the API server.The following fields are removed as they aren't supported by OpenAPI v2.The fields allOf, anyOf, oneOf and not are removedIf nullable: true is set, we drop type, nullable, items and properties because OpenAPI v2 is not able to express nullable. To avoid kubectl to reject good objects, this is necessary.Additional printer columnsThe kubectl tool relies on server-side output formatting. Your cluster's API server decides which columns are shown by the kubectl get command. You can customize these columns for a CustomResourceDefinition. The following example adds the Spec, Replicas, and Age columns.Save the CustomResourceDefinition to resourcedefinition.yaml:apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: name: crontabs.stable.example.com spec: group: stable.example.com scope: Namespaced names: plural: crontabs singular: crontab kind: CronTab shortNames: - ct versions: - name: v1 served: true storage: true schema: openAPIV3Schema: type: object properties: spec: type: object properties: cronSpec: type: string image: type: string replicas: type: integer additionalPrinterColumns: - name: Spec type: string description: The cron spec defining the interval a CronJob is run jsonPath: .spec.cronSpec - name: Replicas type: integer description: The number of jobs launched by the CronJob jsonPath: .spec.replicas - name: Age type: date jsonPath: .metadata.creationTimestamp Create the CustomResourceDefinition:kubectl apply -f resourcedefinition.yaml Create an instance using the my-crontab.yaml from the previous section.Invoke the server-side printing:kubectl get crontab my-new-cron-object Notice the NAME, SPEC, REPLICAS, and AGE columns in the output:NAME SPEC REPLICAS AGE my-new-cron-object * * * * * 1 7s Note:The NAME column is implicit and does not need to be defined in the CustomResourceDefinition.PriorityEach column includes a priority field. Currently, the priority differentiates between columns shown in standard view or wide view (using the -o wide flag).Columns with priority 0 are shown in standard view.Columns with priority greater than 0 are shown only in wide view.TypeA column's type field can be any of the following (compare OpenAPI v3 data types):integer – non-floating-point numbersnumber – floating point numbersstring – stringsboolean – true or falsedate – rendered differentially as time since this timestamp.If the value inside a CustomResource does not match the type specified for the column, the value is omitted. Use CustomResource validation to ensure that the value types are correct.FormatA column's format field can be any of the following:int32int64floatdoublebytedatedate-timepasswordThe column's format controls the style used when kubectl prints the value.Field selectorsField Selectors let clients select custom resources based on the value of one or more resource fields.All custom resources support the metadata.name and metadata.namespace field selectors.Fields declared in a CustomResourceDefinition may also be used with field selectors when included in the spec.versions[*].selectableFields field of the CustomResourceDefinition.Selectable fields for custom resourcesFEATURE STATE: Kubernetes v1.32 [stable] (enabled by default: true)The spec.versions[*].selectableFields field of a CustomResourceDefinition may be used to declare which other fields in a custom resource may be used in field selectors with the feature of CustomResourceFieldSelectors feature gate (This feature gate is enabled by default since Kubernetes v1.31). The following example adds the .spec.color and .spec.size fields as selectable fields.Save the CustomResourceDefinition to shirt-resource-definition.yaml:customresourcedefinition/shirt-resource-definition.yaml apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: name: shirts.stable.example.com spec: group: stable.example.com scope: Namespaced names: plural: shirts singular: shirt kind: Shirt versions: - name: v1 served: true storage: true schema: openAPIV3Schema: type: object properties: spec: type: object properties: color: type: string size: type: string selectableFields: - jsonPath: .spec.color - jsonPath: .spec.size additionalPrinterColumns: - jsonPath: .spec.color name: Color type: string - jsonPath: .spec.size name: Size type: string Create the CustomResourceDefinition:kubectl apply -f https://k8s.io/examples/customresourcedefinition/shirt-resource-definition.yaml Define some Shirts by editing shirt-resources.yaml; for example:customresourcedefinition/shirt-resources.yaml --- apiVersion: stable.example.com/v1 kind: Shirt metadata: name: example1 spec: color: blue size: S --- apiVersion: stable.example.com/v1 kind: Shirt metadata: name: example2 spec: color: blue size: M --- apiVersion: stable.example.com/v1 kind: Shirt metadata: name: example3 spec: color: green size: M Create the custom resources:kubectl apply -f https://k8s.io/examples/customresourcedefinition/shirt-resources.yaml Get all the resources:kubectl get shirts.stable.example.com The output is:NAME COLOR SIZE example1 blue S example2 blue M example3 green M Fetch blue shirts (retrieve Shirts with a color of blue):kubectl get shirts.stable.example.com --field-selector spec.color=blue Should output:NAME COLOR SIZE example1 blue S example2 blue M Get only resources with a color of green and a size of M:kubectl get shirts.stable.example.com --field-selector spec.color=green,spec.size=M Should output:NAME COLOR SIZE example2 blue M SubresourcesCustom resources support /status and /scale subresources.The status and scale subresources can be optionally enabled by defining them in the CustomResourceDefinition.Status subresourceWhen the status subresource is enabled, the /status subresource for the custom resource is exposed.The status and the spec stanzas are represented by the .status and .spec JSONPaths respectively inside of a custom resource.PUT requests to the /status subresource take a custom resource object and ignore changes to anything except the status stanza.PUT requests to the /status subresource only validate the status stanza of the custom resource.PUT/POST/PATCH requests to the custom resource ignore changes to the status stanza.The .metadata.generation value is incremented for all changes, except for changes to .metadata or .status.Only the following constructs are allowed at the root of the CRD OpenAPI validation schema:descriptionexampleexclusiveMaximumexclusiveMinimumexternalDocsformatitemsmaximummaxItemsmaxLengthminimumminItemsminLengthmultipleOfpatternpropertiesrequiredtitletypeuniqueItemsScale subresourceWhen the scale subresource is enabled, the /scale subresource for the custom resource is exposed. The autoscaling/v1.Scale object is sent as the payload for /scale.To enable the scale subresource, the following fields are defined in the CustomResourceDefinition.specReplicasPath defines the JSONPath inside of a custom resource that corresponds to scale.spec.replicas.It is a required value.Only JSONPaths under .spec and with the dot notation are allowed.If there is no value under the specReplicasPath in the custom resource, the /scale subresource will return an error on GET.statusReplicasPath defines the JSONPath inside of a custom resource that corresponds to scale.status.replicas.It is a required value.Only JSONPaths under .status and with the dot notation are allowed.If there is no value under the statusReplicasPath in the custom resource, the status replica value in the /scale subresource will default to 0.labelSelectorPath defines the JSONPath inside of a custom resource that corresponds to Scale.Status.Selector.It is an optional value.It must be set to work with HPA and VPA.Only JSONPaths under .status or .spec and with the dot notation are allowed.If there is no value under the labelSelectorPath in the custom resource, the status selector value in the /scale subresource will default to the empty string.The field pointed by this JSON path must be a string field (not a complex selector struct) which contains a serialized label selector in string form.In the following example, both status and scale subresources are enabled.Save the CustomResourceDefinition to resourcedefinition.yaml:apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: name: crontabs.stable.example.com spec: group: stable.example.com versions: - name: v1 served: true storage: true schema: openAPIV3Schema: type: object properties: spec: type: object properties: cronSpec: type: string image: type: string replicas: type: integer status: type: object properties: replicas: type: integer labelSelector: type: string # subresources describes the subresources for custom resources. subresources: # status enables the status subresource. status: {} # scale enables the scale subresource. scale: # specReplicasPath defines the JSONPath inside of a custom resource that corresponds to Scale.Spec.Replicas. specReplicasPath: .spec.replicas # statusReplicasPath defines the JSONPath inside of a custom resource that corresponds to Scale.Status.Replicas. statusReplicasPath: .status.replicas # labelSelectorPath defines the JSONPath inside of a custom resource that corresponds to Scale.Status.Selector. labelSelectorPath: .status.labelSelector scope: Namespaced names: plural: crontabs singular: crontab kind: CronTab shortNames: - ct And create it:kubectl apply -f resourcedefinition.yaml After the CustomResourceDefinition object has been created, you can create custom objects.If you save the following YAML to my-crontab.yaml:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: cronSpec: "* * * * */5" image: my-awesome-cron-image replicas: 3 and create it:kubectl apply -f my-crontab.yaml Then new namespaced RESTful API endpoints are created at:/apis/stable.example.com/v1/namespaces/*/crontabs/status and/apis/stable.example.com/v1/namespaces/*/crontabs/scale A custom resource can be scaled using the kubectl scale command. For example, the following command sets .spec.replicas of the custom resource created above to 5:kubectl scale --replicas=5 crontabs/my-new-cron-object crontabs "my-new-cron-object" scaled kubectl get crontabs my-new-cron-object -o jsonpath='{.spec.replicas}' 5 You can use a PodDisruptionBudget to protect custom resources that have the scale subresource enabled.CategoriesCategories is a list of grouped resources the custom resource belongs to (eg. all). You can use kubectl get <category-name> to list the resources belonging to the category.The following example adds all in the list of categories in the CustomResourceDefinition and illustrates how to output the custom resource using kubectl get all.Save the following CustomResourceDefinition to resourcedefinition.yaml:apiVersion: apiextensions.k8s.io/v1 kind: CustomResourceDefinition metadata: name: crontabs.stable.example.com spec: group: stable.example.com versions: - name: v1 served: true storage: true schema: openAPIV3Schema: type: object properties: spec: type: object properties: cronSpec: type: string image: type: string replicas: type: integer scope: Namespaced names: plural: crontabs singular: crontab kind: CronTab shortNames: - ct # categories is a list of grouped resources the custom resource belongs to. categories: - all and create it:kubectl apply -f resourcedefinition.yaml After the CustomResourceDefinition object has been created, you can create custom objects.Save the following YAML to my-crontab.yaml:apiVersion: "stable.example.com/v1" kind: CronTab metadata: name: my-new-cron-object spec: cronSpec: "* * * * */5" image: my-awesome-cron-image and create it:kubectl apply -f my-crontab.yaml You can specify the category when using kubectl get:kubectl get all and it will include the custom resources of kind CronTab:NAME AGE crontabs/my-new-cron-object 3s What's nextRead about custom resources.See CustomResourceDefinition.Serve multiple versions of a CustomResourceDefinition.