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Configuration

Overview

Customize how kbld:

  • searches for image references,
  • resolves image names,
  • builds images from source, and
  • pushes built images to container registries.

This is done by supplying one or more configuration files. These files are in the Kubernetes resource format (i.e. has apiVersion and kind). kbld consumes and removes such files from its output.

A kbld configuration file is structured like so:

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
minimumRequiredVersion: 0.31.0

searchRules: ...
overrides: ...
sources: ...
destinations: ...

where:

  • minimumRequiredVersion (optional; semver) — specifies the minimum required version of kbld needed to work with this configuration.

and any combination of the follow four sections:

  • searchRules — a list of Search Rules that kbld follows to locate container image references within the input files.
  • overrides — a list of Overrides that kbld applies to found container image references before it attempts to resolve or build the actual image.
  • sources — a list of Sources, each of which describes where to find the source that makes up the contents of a given image and which build tool to use to construct it.
  • destinations — a list of Destinations, each of which describes where (i.e. to which container registry) to publish a given image.

(Note: prior to v0.28.0, different types of configuration were supplied in different kind of files: kind: Sources, kind: ImageDestinations, kind: ImageOverrides, kind: ImageKeys. Since v0.28.0, all such configuration can be specified in one kind of file: kind: Config; this is recommended.)


Search Rules

kbld scans input files for references to container images. Search rules describe how kbld should identify those references and how to process them.

A search rule has two parts:

  • conditions for matching (either by key, by value, or both), and
  • a strategy for how to parse and update a matched item.

A search rule is expressed like this:

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
searchRules:
- keyMatcher: ...
  valueMatcher: ...
  updateStrategy: ...

where a rule consists of one or both of the following…

  • keyMatcher a Key Matcher — identifies container image references based on an item’s key.
  • valueMatcher a Value Matcher — identifies container image references based on an item’s value.

(If both are specified, their results are “and’ed” together.)

…and optionally,

  • updateStrategy an Update Strategy — what kbld should do with the matched container image reference.

Multiple Matching search rules
If multiple search rules match the same item, the rule that was defined first is applied.

Note: kbld includes its own Default Search Rules

Key Matcher

Specifies whether a given key indicates that its corresponding value is an image reference.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
searchRules:
- keyMatcher:
    name:
    path:

where:

  • name (string) specifies the key name (e.g. sidecarImage)
  • path (array) specifies key path from the root of the YAML document.
    Each path part can be one of:
    • the literal key name. (e.g. [data, sidecarImage] maps to data.sidecarImage)
    • an array indexing tactic (choose one):
      • index: (int) — search one element in the array at the (zero-based) index given.
        (example: [spec, template, spec, containers, {index: 0}, image])
      • allIndexes: (bool) — search all elements in the array.
        (example: [spec, images, {allIndexes: true}])

Value Matcher

Specifies whether a given value contains an image reference.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
searchRules:
- valueMatcher:
    ( image | imageRepo ):

where (choose one):

  • image (string) value to match exactly
  • imageRepo (string) of values in the format ([registry]repo[:tag]\[@sha256:...]), the value of the repo portion.
    (example: imageRepo: gcr.io/project/app
    matches gcr.io/projects/app:v1.1 and gcr.io/projects/app@sha256:f33e111...
    but not gcr.io/projects/app_v1)

Update Strategy

Given a container image reference identified by one or more matchers, an Update Strategy describes how to update that value (v0.21.0+).

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
searchRules:
- ( keyMatcher | valueMatcher ): ...
  updateStrategy:
    yaml:
      searchRules: ...
    json:
      searchRules: ...
    none: {}
    entireValue: {}

where (choose one):

  • yaml parses YAML and identifies image refs by specified search rules
    • searchRules — one or more Search Rules, scoped to the parsed content.
  • json parses JSON and identifies image refs by specified search rules
    • searchRules — one or more Search Rules, scoped to the parsed content.
  • none (empty) excludes value from processing (v0.22.0+)
  • entireValue (empty; default) uses the exact value as the image reference.

Example for updateStrategy that parses YAML

---
kind: ConfigMap
metadata:
  name: config
data:
  data.yml: |
    name: nginx
    image: nginx # <-- below config finds and updates this image    
---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
minimumRequiredVersion: 0.15.0
searchRules:
- keyMatcher:
    name: data.yml
  updateStrategy:
    yaml:
      searchRules:
      - keyMatcher:
          name: image

Note that in the ConfigMap, that /data/data.yml holds a multi-line string. That string happens to also be in YAML format. When that YAML is parsed, the image key holds a container image reference.

Default Search Rules

After custom search rules have been processed, kbld appends the following search rule:

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
searchRules:
- keyMatcher:
    name: image
  updateStrategy:
    entireValue: {}

Overrides

After kbld searches for container image references, it applies a set of “overrides” which effectively rewrite those references. It does this before attempting to build the corresponding image or resolve it to a digest reference.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
overrides:
- image:
  newImage:
  preresolved:
  tagSelection: ...

where:

  • image (required; string) exact value found while searching for container image references.
  • newImage (required; string) value with which to replace/override. This ought to be an image reference in the format [registry]repo[:tag]\[@sha256:...].
    Examples:
    • nginx
    • quay.io/bitnami/nginx
    • nginx:1.21.1
    • nginx@sha256:a05b0cd...
    • index.docker.io/library/nginx@sha256:a05b0cd...
  • preresolved (optional; bool) specifies if newImage should be used as is (rather than be [re]resolved to a digest reference).
  • tagSelection (optional; VersionSelection) when newImage is being resolved, specifies how to select the tag part of the reference before resolving to a digest reference. (Available as of v0.28.0+)
    • In this case, newImage must not have a tag or digest part (e.g. gcr.io/my-corp/app).

Example: Static Rewrite

With the following configuration, any container image reference of the value "unknown" will get rewritten to "docker.io/library/nginx:1.14.2" before being resolved to a digest reference.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
overrides:
- image: unknown
  newImage: docker.io/library/nginx:1.14.2

Example: Preresolved

This configuration replaces references of "unknown" with "docker.io/library/nginx:1.14.2". It short-circuits any building, resolution, or even connecting to a registry to obtain metadata about the image reference.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
overrides:
- image: unknown
  newImage: docker.io/library/nginx:1.14.2
  preresolved: true

Example: Dynamic Tag Selection

This configuration first rewrites references of "unknown" with "docker.io/library/nginx". It then queries the registry to locate the latest version just prior to 1.15.0 (which turns out to be 1.14.2).

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
overrides:
- image: unknown
  newImage: docker.io/library/nginx
  tagSelection:
    semver:
      constraints: "<1.15.0"

Sources

Rather than resolve an image reference, kbld can build the image from source. More precisely, kbld can be configured to use one of the many image building tools it integrates with to construct the image from source. For an overview, see Building Images.

Such integration is enabled by configuring a “Source”:

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
sources:
- image: image1
  path: src/
  ( docker | pack | kubectlBuildkit | ko | bazel ): ...

where:

  • image (required; string) exact value found while searching for container image references.
  • path (required; string) filesystem path to the source for the to-be-built image
  • a builder configuration (optional; choose one) — name/configure a specific image builder tool:
    • docker: (default) use Docker to build from source.
    • pack: use Pack to build the image via buildpacks from source.
    • kubectlBuildkit: use Buildkit CLI for kubectl to build the image via a Kubernetes cluster form source.
    • ko: use ko to build the image from Go source.
    • bazel: use Bazel to build the image via Bazel Container Image Rules.

Docker

Using this integration requires:

The Docker CLI must be on the $PATH.

To configure an image to be built via Docker, include a docker:-flavored Source:

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
sources:
- image: image1
  path: src/
  docker:
    build:
      target: some-target
      pull: true
      noCache: true
      file: hack/Dockerfile.dev
      buildkit: true
      rawOptions: ["--squash", "--build-arg", "ARG_IN_DOCKERFILE=value"]

where:

  • target (string): the target build stage to build (no default)
  • pull (bool): always attempt to pull a newer version of the image (default is false)
  • noCache (bool): do not use cache when building the image (default is false)
  • file (string): name of the Dockerfile (default is Dockerfile)
  • buildkit (bool): enable Builtkit for this build.
  • rawOptions ([]string): Refer to docker build reference for all available options

Pack

Using this integration requires:

The Pack CLI must be on the $PATH.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
sources:
- image: image1
  path: src/
  pack:
    build:
      builder: cloudfoundry/cnb:bionic

where (all options are optional):

  • builder (string): Set builder image (required)
  • buildpacks ([]string): Set list of buildpacks to be used (no default)
  • clearCache (bool): Clear cache before building image (default is false)
  • rawOptions ([]string): Refer to pack build -h for all available flags

BuildKit CLI for kubectl

Available as of v0.28.0+

Using this integration requires:

The kubectl CLI must be on the $PATH.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
sources:
- image: image1
  path: src/
  kubectlBuildkit:
    build:
      target: "some-target"
      pull: true
      noCache: true
      file: "hack/Dockefile.dev"
      rawOptions: ["--platform=..."]

where (all options are optional):

  • target (string): Set the target build stage to build (no default)
  • pull (bool): Always attempt to pull a newer version of the image (default is false)
  • noCache (bool): Do not use cache when building the image (default is false)
  • file (string): Name of the Dockerfile (default is Dockerfile)
  • rawOptions ([]string): Refer to kubectl buildkit build -h for all available options

Authenticating to Registry for Pushing Images

To provide registry credentials to the builder, create a Kubernetes docker-registry secret:

kubectl create secret docker-registry buildkit --docker-server=https://index.docker.io/v1/ --docker-username=my-user --docker-password=my-password

See project site for details: buildkit-cli-for-kubectl.

ko

Available as of v0.28.0+

Using this integration requires:

The ko CLI must be on the $PATH.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
sources:
- image: image1
  path: ./src/
  ko:
    build:
      rawOptions: ["--disable-optimizations"]

where:

  • rawOptions (optional; []string): Refer to ko publish -h for all available options.

By default kbld provides the --local flag

Bazel

Available as of v0.31.0+

Using this integration requires:

The bazel CLI must be on the $PATH.

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
sources:
  - image: image1
    path: ./src/
    bazel:
      run:
        target: :image1-go-container
        rawOptions: ["--platforms=@io_bazel_rules_go//go/toolchain:linux_amd64"]

where:

Using Language-specific Container Rules

This integration invokes the bazel run command (as opposed to the bazel build command).

Typically, when configuring the Bazel integration with kbld, the specified target is one of the Container Image Rules.

With such rules, the bazel build command produces the artifacts that make up all images described in the BUILD, but stops short of loading any image into the Docker daemon. In order for an image to be pushed to a registry (i.e. published), it must first be loaded into the local Docker daemon. The bazel run command takes that additional step to execute the script that performs that docker load for the named target, only.

For so-called lang_image rules, this also results in launching a container from that image (i.e. docker run the built image). For our purposes, this is undesirable because it effectively halts the build.

To skip this that launching step, append the args -- --norun via the rawOptions: key:

...
    bazel:
      run:
        target: :image1-go-container
        rawOptions: ["--", "--norun"]

See also https://github.com/bazelbuild/rules_docker#using-with-docker-locally.


Destinations

Once kbld has processed the found container image references (either resolved or built them), it can publish those images to a different registry (on an image-by-image basis).

Pushing images to registries through this configuration requires:

(In the case where all published images are built through BuildKit CLI for kubectl, Docker is not required; publishing happens from within the Kubernetes cluster).

Do this by configuring one or more “destinations”:

---
apiVersion: kbld.k14s.io/v1alpha1
kind: Config
destinations:
- image: adservice
  newImage: docker.io/dkalinin/microservices-demo-adservice
  tags: [latest, tag2]

where:

  • image (required; string) exact value found while searching for container image references.
  • newImage (required; string) image destination (i.e. fully qualified registry location for the image)
  • tags (optional; array of strings) tags to apply to pushed images (v0.26.0+)