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What is Shipwright?

Shipwright is a Kubernetes-native build framework that provides a declarative API for building container images. It abstracts away the complexity of container builds by defining BuildStrategies that encapsulate build tools and processes. migetpacks integrates with Shipwright as a ClusterBuildStrategy, allowing you to build application containers directly from source code using Kubernetes-native resources.

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ClusterBuildStrategy

The ClusterBuildStrategy defines how migetpacks runs inside the cluster. It specifies the builder image, volumes, and parameters available to builds. 
apiVersion: shipwright.io/v1beta1
kind: ClusterBuildStrategy
metadata:
  name: migetpacks
spec:
  volumes:
    - name: results
      emptyDir: {}
    - name: build-cache
      persistentVolumeClaim:
        claimName: build-cache  # RWX PVC shared across builds
  steps:
    - name: build
      image: miget/migetpacks:latest
      securityContext:
        privileged: true  # Required for Docker-in-Docker
      volumeMounts:
        - name: results
          mountPath: /workspace/output
        - name: build-cache
          mountPath: /cache
      env:
        - name: SOURCE_DIR
          value: $(params.shp-source-root)
        - name: OUTPUT_IMAGE
          value: $(params.shp-output-image)
        - name: RESULT_FILE
          value: /workspace/output/build-result.json
        - name: BUILD_CACHE_DIR
          value: /cache
      resources:
        requests:
          cpu: "500m"
          memory: "1Gi"
        limits:
          cpu: "2"
          memory: "4Gi"
The privileged: true security context is required because migetpacks uses Docker-in-Docker (DinD) to build container images.

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Volumes

migetpacks uses several volume types in Shipwright builds:
VolumeTypePurpose
SourceShipwright-managedSource code from Git repository
ResultsemptyDirBuild result JSON for post-build steps
Build CachePVC (RWX)Shared package manager cache across builds

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Environment Variables

Pass environment variables to customize the build behavior. These can be set directly in the BuildStrategy or passed through the Build resource. 
env:
  - name: LANGUAGE
    value: ruby
  - name: PORT
    value: "3000"
  - name: USE_DHI
    value: "true"
  - name: REGISTRY_MIRROR
    value: https://registry.example.io/mirror
  - name: CACHE_IMAGE
    value: registry.io/myapp:cache
Any environment variable not in the known builder variables list is automatically injected into the generated Dockerfile as an ENV statement. This is useful for passing build-time configuration like NODE_OPTIONS or RAILS_MASTER_KEY.

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RESULT_FILE for Post-Build Steps

When RESULT_FILE is set, migetpacks writes a JSON file containing build results. This enables post-build steps (like deployment notifications) to access build metadata. The builder always exits with code 0 to ensure post-build steps execute. Check the status field in the result JSON to determine if the build succeeded or failed. 
volumes:
  - name: results
    emptyDir: {}
steps:
  - name: build
    image: miget/migetpacks:latest
    volumeMounts:
      - name: results
        mountPath: /workspace/output
    env:
      - name: RESULT_FILE
        value: /workspace/output/build-result.json

  - name: notify
    image: your-rabbitmq-publisher:latest
    volumeMounts:
      - name: results
        mountPath: /workspace/output
    # Reads /workspace/output/build-result.json and publishes to RabbitMQ

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Build Resource

The Build resource defines what to build and where to push the result. 
apiVersion: shipwright.io/v1beta1
kind: Build
metadata:
  name: my-app
  namespace: default
spec:
  source:
    type: Git
    git:
      url: https://github.com/your-org/your-app.git
      revision: main
    contextDir: .  # Or a subdirectory for monorepos
  strategy:
    name: migetpacks
    kind: ClusterBuildStrategy
  output:
    image: registry.io/your-org/your-app:latest
    credentials:
      name: registry-credentials  # Secret with .dockerconfigjson
  env:
    - name: USE_DHI
      value: "true"
    - name: PORT
      value: "3000"
  timeout: 10m

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BuildRun Resource

A BuildRun triggers an actual build execution. 
apiVersion: shipwright.io/v1beta1
kind: BuildRun
metadata:
  name: my-app-run-1
  namespace: default
spec:
  build:
    name: my-app
  env:
    - name: NO_CACHE
      value: "true"  # Force fresh build for this run
  serviceAccount:
    name: build-sa
  timeout: 15m
You can also create a BuildRun that overrides the output image: 
apiVersion: shipwright.io/v1beta1
kind: BuildRun
metadata:
  generateName: my-app-run-
  namespace: default
spec:
  build:
    name: my-app
  output:
    image: registry.io/your-org/your-app:$(git-sha)
    credentials:
      name: registry-credentials

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Full Example with Cache and Results

This complete example shows a ClusterBuildStrategy with build caching, registry mirror, and a post-build notification step: 
apiVersion: shipwright.io/v1beta1
kind: ClusterBuildStrategy
metadata:
  name: migetpacks-full
spec:
  volumes:
    - name: results
      emptyDir: {}
    - name: build-cache
      persistentVolumeClaim:
        claimName: migetpacks-cache  # RWX PVC
  steps:
    - name: build
      image: miget/migetpacks:latest
      securityContext:
        privileged: true
      volumeMounts:
        - name: results
          mountPath: /workspace/output
        - name: build-cache
          mountPath: /cache
      env:
        - name: SOURCE_DIR
          value: $(params.shp-source-root)
        - name: OUTPUT_IMAGE
          value: $(params.shp-output-image)
        - name: RESULT_FILE
          value: /workspace/output/build-result.json
        - name: BUILD_CACHE_DIR
          value: /cache
        - name: REGISTRY_MIRROR
          value: https://registry.example.io/mirror
        - name: USE_DHI
          value: "true"
        - name: CACHE_IMAGE
          value: $(params.shp-output-image)-cache
        - name: CACHE_MODE
          value: max
      resources:
        requests:
          cpu: "1"
          memory: "2Gi"
        limits:
          cpu: "4"
          memory: "8Gi"

    - name: notify
      image: your-notification-service:latest
      volumeMounts:
        - name: results
          mountPath: /workspace/output
      env:
        - name: RESULT_PATH
          value: /workspace/output/build-result.json
        - name: RABBITMQ_URL
          valueFrom:
            secretKeyRef:
              name: rabbitmq-credentials
              key: url