6.4. Use 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> 

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     output:
       to:
         kind: ImageStreamTag
         name: sample-custom:latest

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   Specify your project name.

2. Create the BuildConfig:

   $ oc create -f buildconfig.yaml

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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: {}

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4. Create the imagestream:

   $ oc create -f imagestream.yaml

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5. Run your custom build:

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

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   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.