6.4. Use custom builder image

You can define a BuildConfig object that uses the custom strategy in conjunction with your custom builder image to execute your custom build logic.

Prerequisites

  • Define all the required inputs for new custom builder image.
  • Build your custom builder image.

Procedure

  1. Create a file named buildconfig.yaml. This file defines the BuildConfig object that is created in your project and executed: 

    kind: BuildConfig
apiVersion: v1
metadata:
  name: sample-custom-build
  labels:
    name: sample-custom-build
  annotations:
    template.alpha.openshift.io/wait-for-ready: 'true'
spec:
  strategy:
    type: Custom
    customStrategy:
      forcePull: true
      from:
        kind: ImageStreamTag
        name: custom-builder-image:latest
        namespace: <yourproject> 1
  output:
    to:
      kind: ImageStreamTag
      name: sample-custom:latest
    1
    Specify your project name.

  2. Create the BuildConfig: 

    $ oc create -f buildconfig.yaml

  3. Create a file named imagestream.yaml. This file defines the image stream to which the build will push the image: 

    kind: ImageStream
apiVersion: v1
metadata:
  name: sample-custom
spec: {}

  4. Create the imagestream: 

    $ oc create -f imagestream.yaml

  5. Run your custom build: 

    $ oc start-build sample-custom-build -F

    When the build runs, it launches a pod running the custom builder image that was built earlier. The pod runs the build.sh logic that is defined as the entrypoint for the custom builder image. The build.sh logic invokes Buildah to build the dockerfile.sample that was embedded in the custom builder image, and then uses Buildah to push the new image to the sample-custom image stream.