Image Resources

Image resources provide a configuration for kpack to build and maintain a docker image utilizing Cloud Native Buildpacks. kpack will monitor the inputs to the image resource to rebuild the OCI image when the underlying source or the builder's buildpacks or stacks have changed.

Corresponding kp cli command docs here.

The following defines the relevant fields of the image resource spec in more detail:

tag: The image tag.
additionalTags: Any additional list of image tags that should be published. This list of tags is mutable.
builder: Configuration of the builder resource the image builds will use. See more info Builder Configuration.
serviceAccountName: The Service Account name that will be used for credential lookup.
source: The source code that will be monitored/built into images. See the Source Configuration section below.
cache: Caching configuration, two variants are available:
- volume.size: Creates a Volume Claim of the given size
- volume.storageClassName: (Optional) Creates a Volume Claim of the given storageClassName. If unset, the default storage class is used. The field is immutable.
- registry.tag: Creates an image with cached contents
failedBuildHistoryLimit: The maximum number of failed builds for an image that will be retained.
successBuildHistoryLimit: The maximum number of successful builds for an image that will be retained.
imageTaggingStrategy: Allow for builds to be additionally tagged with the build number. Valid options are None and BuildNumber.
build: Configuration that is passed to every image build. See Build Configuration section below.
defaultProcess: The default process type for the built OCI image
projectDescriptorPath: Path to the project descriptor file relative to source root dir or subPath if set. If unset, kpack will look for project.toml at the root dir or subPath if set.
cosign: Configuration for additional cosign image signing. See Cosign Configuration section below.

Configuring Tags

The tag field is the location the built OCI image will be written to for each build. This field is immutable.

Examples:

tag: dockerhubuser/repo
tag: dockerhubuser/repo:my-image
tag: gcr.io/project/repo

The additionalTags is a list of locations the built OCI image will be written to in addition to the tag. Additional tags must be in the same registry as the tag. Cross registry exporting is not supported. This field can be modified.

Example:

tag: my-registry.io/project/repo 
additionalTags:
- my-registry.io/project/repo:some-version
- my-registry.io/project/repo:some-metadata
- my-registry.io/project/other-repo

Builder Configuration

The builder field describes the builder resource that will build the OCI images for a provided image configuration. It can be defined in exactly one of the following ways:

Cluster Builder
```
builder:
    name: cluster-builder-name
    kind: ClusterBuilder
```
- name: The name of the ClusterBuilder resource in kubernetes.
- kind: The type as defined in kubernetes. This will always be ClusterBuilder.
Namespaced Builder
```
builder:
    name: builder-name
    kind: Builder
```
- name: The name of the Builder resource in kubernetes.
- kind: The type as defined in kubernetes. This will always be Builder.

Note: This image resource can only reference builders defined in the same namespace. This is not true for ClusterBuilders because they are not namespace scoped.

Source Configuration

The source field is a composition of a source code location and a subpath. It can be configured in exactly one of the following ways:

Git
```
source:
  git:
    url: ""
    revision: ""
    initializeSubmodules: false
  subPath: ""
```
- git: (Source Code is a git repository)
  - url: The git repository url. Both https and ssh formats are supported; with ssh format requiring a ssh secret.
  - revision: The git revision to use. This value may be a commit sha, branch name, or tag.
  - initializeSubmodules: Initialize submodules inside repo, recurses up to a max depth of 10 submodules.
- subPath: A subdirectory within the source folder where application code resides. Can be ignored if the source code resides at the root level.
Blob
```
source:
  blob:
    url: ""
    stripComponents: 0
  subPath: ""
```
- blob: (Source Code is a blob/jar in a blobstore)
  - url: The URL of the source code blob. This blob needs to either be publicly accessible or have the access token in the URL
  - stripComponents: Optional number of directory components to strip from the blobs content when extracting.
- subPath: A subdirectory within the source folder where application code resides. Can be ignored if the source code resides at the root level.
Registry
```
source:
  registry:
    image: ""
    imagePullSecrets:
    - name: ""
  subPath: ""
```
- registry ( Source code is an OCI image in a registry that contains application source)
  - image: Location of the source image
  - imagePullSecrets: A list of dockercfg or dockerconfigjson secret names required if the source image is private
- subPath: A subdirectory within the source folder where application code resides. Can be ignored if the source code resides at the root level.

Build Configuration

The build field on the image resource can be used to configure env variables required during the build process, to configure resource limits on CPU and memory, and to configure pod tolerations, node selector, build timeout (specified in seconds), and affinity. To configure "Creation Time" of the built app image, pass in the unix EPOCH timestamp (i.e "1667243396") as a string or use "now" to use the current time.

build:
  env:
    - name: "name of env variable"
      value: "value of the env variable"
  resources:
      requests:
        cpu: "0.25"
        memory: "128M"
      limits:
        cpu: "0.5"
        memory: "256M"
  tolerations:
    - key: "key1"
      operator: "Exists"
      effect: "NoSchedule"
  nodeSelector:
    disktype: ssd
  buildTimeout: 1600
  creationTime: "now"
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
          - matchExpressions:
              - key: kubernetes.io/e2e-az-name
                operator: In
                values:
                  - e2e-az1
                  - e2e-az2

See the kubernetes documentation on setting environment variables and resource limits and requests for more information.

Cosign Configuration

Cosign Signing Secret

OCI images built by kpack can be signed with cosign when a cosign formatted secret is added to the service account configured on the image resource. The secret can be added using the cosign CLI or manually.

To create a cosign signing secret through the cosign CLI, when targetted to the Kubernetes cluster, use: cosign generate-key-pair k8s://[NAMESPACE]/[NAME]

Alternatively, create the cosign secret and provide your own cosign key files manually to Kubernetes by running the following command:

% kubectl create secret generic <secret-name> --from-literal=cosign.password=<password> --from-file=</path/to/cosign.key>

<secret-name>: The name of the secret. Ensure that the secret is created in the same namespace as the eventual image resource.
<password>: The password provided to encrypt the private key. If not present, an empty password will be used.
</path/to/cosign.key>: The cosign private key file generated with cosign generate-key-pair.

After adding the cosign secret, the secret must be added to the list of secrets on the service account that the image is configured with.

Adding Cosign Annotations

By default, the build number and build timestamp information will be added to the cosign signing annotations. Users can specify additional cosign annotations under the spec key.

cosign:
  annotations:
  - name: "annotationName"
    value: "annotationValue"

One way these annotations can be viewed is through verifying cosign signatures. The annotations will be under the optional key in the verified JSON response. For example, this can be done with:

% cosign verify -key /path/to/cosign.pub registry.example.com/project/image@sha256:<DIGEST>

Which provides a JSON response similar to:

{
  "critical": {
    "identity": {
      "docker-reference": "registry.example.com/project/image"
    }, "image": {
      "docker-manifest-digest": "sha256:<DIGEST>"
    }, "type": "cosign container image signature"
  }, "optional": {
    "buildNumber": "1",
    "buildTimestamp": "20210827.175240",
    "annotationName": "annotationValue"
  }
}

Push Cosign Signature to a Different Location

Cosign signatures can be pushed to a different registry from where the built OCI image is written to. To enable this, add the corresponding annotation to the cosign secret resource.

metadata:
  name: ...
  namespace: ...
  annotations:
    kpack.io/cosign.repository: other.registry.com/project/image
data:
  cosign.key: ...
  cosign.password: ...

This will be equivalent to setting COSIGN_REPOSITORY as specified in cosign Specifying Registry

The service account configured on the image resource must have registry credentials for the other registry configured in the secrets list (they do not need to be configured as imagePullSecrets).

It should be noted that if you wish to push the signatures to the same registry but a different repository as the image resource tag, the credential used must have access to both paths. You cannot use two separate credentials for the same registry.

Cosign Legacy Docker Media Types

To sign docker images in a registry that does not fully support OCI media types, legacy equivalents can be used by adding the corresponding annotation to the cosign secret resource:

metadata:
  name: ...
  namespace: ...
  annotations:
    kpack.io/cosign.docker-media-types: "1"
data:
  cosign.key: ...
  cosign.password: ...

This will be equivalent to setting COSIGN_DOCKER_MEDIA_TYPES=1 as specified in the cosign registry-support

Sample Image Resource with a Git Source

apiVersion: kpack.io/v1alpha2
kind: Image
metadata:
  name: sample-image
  namespace: build-namespace
spec:
  tag: gcr.io/project-name/app
  serviceAccountName: service-account
  builder:
    name: sample-builder
    kind: ClusterBuilder
  cache:
    volume:
      size: "1.5Gi" # Optional, if not set then the caching feature is disabled
      storageClassName: "my-storage-class" # Optional, if not set then the default storageclass is used
  failedBuildHistoryLimit: 5 # Optional, if not present defaults to 10
  successBuildHistoryLimit: 5 # Optional, if not present defaults to 10
  source:
    git:
      url: https://github.com/buildpack/sample-java-app.git
      revision: main
  build: # Optional
    env:
      - name: BP_JAVA_VERSION
        value: 8.*
    resources:
      limits:
        cpu: 100m
        memory: 1G
      requests:
        cpu: 50m
        memory: 512M

Source for github can also be specified in the ssh format if there is a corresponding ssh secret

  source:
    git:
      url: git@github.com/buildpack/sample-java-app.git
      revision: main

Sample Image Resource with hosted zip or jar as a source

apiVersion: kpack.io/v1alpha2
kind: Image
metadata:
  name: sample-image
  namespace: build-namespace
spec:
  tag: gcr.io/project-name/app
  serviceAccountName: service-account
  builder:
    name: sample-builder
    kind: ClusterBuilder
  cache:
    volume:
      size: "1.5Gi" # Optional, if not set then the caching feature is disabled
      storageClassName: "my-storage-class" # Optional, if not set then the default storageclass is used
  failedBuildHistoryLimit: 5 # Optional, if not present defaults to 10
  successBuildHistoryLimit: 5 # Optional, if not present defaults to 10
  source:
    blob:
      url: https://storage.googleapis.com/build-service/sample-apps/spring-petclinic-2.1.0.BUILD-SNAPSHOT.jar
  build: # Optional
    env:
      - name: BP_JAVA_VERSION
        value: 8.*
    resources:
      limits:
        cpu: 100m
        memory: 1G
      requests:
        cpu: 50m
        memory: 512M

Status

When an image resource has successfully built with its current configuration, its status will report the up to date fully qualified built OCI image reference.

If you are using kubectl this information is available with kubectl get <image-resource-name> or kubectl describe <image-resource-name>.

status:
  conditions:
  - lastTransitionTime: "2020-01-17T16:16:36Z"
    status: "True"
    type: Ready
  latestImage: index.docker.io/sample/image@sha256:d3eb15a6fd25cb79039594294419de2328f14b443fa0546fa9e16f5214d61686
  ...

When a build fails its status will report the condition Succeeded=False.

status:
  conditions:
  - lastTransitionTime: "2020-01-17T16:13:48Z"
    status: "False"
    type: Ready
  ...

Legacy apiVersion kpack.io/v1alpha1

Notable deprecations from kpack.io/v1alpha1 include:

Notary image signing
Cloud Native Buildpack service bindings

kpack.io/v1alpha1 will eventually be removed entirely so please migrate existing Image resources to use kpack.io/v1alpha2 apis.

Notary Configuration

apiVersion must be kpack.io/v1alpha1

The optional notary field on the image resource can be used to configure Notary image signing.

notary:
  v1:
    url: "https://example.com/notary"
    secretRef:
      name: "notary-secret"

v1.url: The URL of the notary server.
v1.secretRef.name: A secret containing the encrypted private key and private key password.

Generate Signing Key

To generate a signing key, use the following commands from the Docker Content Trust documentation:

% export DOCKER_CONTENT_TRUST_SERVER=<notary-server-url>
% docker trust key generate my-key
% docker trust signer add --key my-key.pub my-key registry.example.com/org/app

This will generate a private key in ~/.docker/trust/private encrypted with the user provided password.

Create Notary Secret

To create the notary secret used by kpack for image signing, run the following command:

% kubectl create secret generic <secret-name> --from-literal=password=<password> --from-file=$HOME/.docker/trust/private/<hash>.key

<secret-name>: The name of the secret. Ensure that the secret is created in the same namespace as the eventual image resource.
<password>: The password provided to encrypt the private key.
<hash>.key: The private key file.

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image.md

image.md

Image Resources

Configuring Tags

Builder Configuration

Source Configuration

Build Configuration

Cosign Configuration

Cosign Signing Secret

Adding Cosign Annotations

Push Cosign Signature to a Different Location

Cosign Legacy Docker Media Types

Sample Image Resource with a Git Source

Sample Image Resource with hosted zip or jar as a source

Status

Legacy apiVersion kpack.io/v1alpha1

Notary Configuration

Generate Signing Key

Create Notary Secret

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image.md

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image.md

File metadata and controls

Image Resources

Configuring Tags

Builder Configuration

Source Configuration

Build Configuration

Cosign Configuration

Cosign Signing Secret

Adding Cosign Annotations

Push Cosign Signature to a Different Location

Cosign Legacy Docker Media Types

Sample Image Resource with a Git Source

Sample Image Resource with hosted zip or jar as a source

Status

Legacy apiVersion kpack.io/v1alpha1

Notary Configuration

Generate Signing Key

Create Notary Secret