Demo Builds

Welcome — in this lesson we’ll explore OpenShift BuildConfigs and show how to create a new build configuration that switches from a Source (S2I) strategy to a Docker strategy. We will:

Inspect an existing BuildConfig in the web console
Export and simplify the BuildConfig YAML
Change the strategy to Docker and create a matching ImageStream
Start the build and validate the result

Inspect the existing BuildConfig

In the OpenShift console, navigate to the project and open Builds → Build Configs. For this demo the existing BuildConfig is simple-webapp-docker. Clicking the build shows each run, logs, and the Configuration tab where you can inspect details such as:

Build strategy (e.g. Source / Source-to-Image)
Source repository (Git URL)
Output location (ImageStreamTag)
Webhooks that can trigger builds
Environment variables and build events

Example configuration summary visible in the console:

Build Strategy:        Source
Source Repo:           http://192.168.56.150/root/simple-webapp.git
Source Ref:            master
Builder Image:         openshift/python:3.6
Output To:             my-webapplication/simple-webapp:latest
Run Policy:            Serial

Export the BuildConfig YAML and simplify it

Use the console Actions → Edit YAML to export the BuildConfig. The exported YAML contains generated metadata and many fields you don’t need for creating a new BuildConfig (annotations, creationTimestamp, resourceVersion, selfLink, uid, etc.). Strip out these generated fields and keep only the fields required for your new BuildConfig. Example of an exported BuildConfig (full of generated metadata):

apiVersion: build.openshift.io/v1
kind: BuildConfig
metadata:
  annotations:
    openshift.io/generated-by: OpenShiftWebConsole
    creationTimestamp: '2018-04-30T09:38:40Z'
  labels:
    app: simple-webapp
  name: simple-webapp
  namespace: my-webapplication
  resourceVersion: '6089'
  selfLink: >-
    /apis/build.openshift.io/v1/namespaces/my-webapplication/buildconfigs/simple-webapp
  uid: 442c5b3c-4c5a-11e8-aaf2-8e9d9a82d1a9
spec:
  nodeSelector: null
  output:
    to:
      kind: ImageStreamTag
      name: 'simple-webapp:latest'
  postCommit: {}
  resources: {}
  runPolicy: Serial
  source:
    git:
      ref: master
    uri: 'http://192.168.56.150/root/simple-webapp.git'

Table — Common BuildConfig fields you should keep or change:

Field	Purpose	Example / Action
`metadata.name`	BuildConfig name	Change to `simple-webapp-docker`
`metadata.namespace`	Project namespace	`my-webapplication`
`spec.source`	Source repo settings	Keep Git URL and `ref: master`
`spec.strategy`	Build strategy	Change to `type: Docker`
`spec.output.to`	ImageStreamTag target	`simple-webapp-docker:latest`
`spec.triggers`	How builds are started	ImageChange, ConfigChange, Generic (webhook)

Prepare the repository

Before switching to Docker strategy, ensure your Git repo contains a Dockerfile at the repository root (or at the path you reference). DockerStrategy builds use the repository Dockerfile to perform the build.

DockerStrategy builds require a Dockerfile in the repository. Make sure your repo has a valid Dockerfile committed before triggering the Docker build.

Minimal BuildConfig using Docker strategy

After removing unnecessary metadata and updating fields, create a minimal BuildConfig that:

Uses the same Git repository
Outputs to simple-webapp-docker:latest
Uses Docker as the build strategy

apiVersion: build.openshift.io/v1
kind: BuildConfig
metadata:
  name: simple-webapp-docker
  namespace: my-webapplication
spec:
  runPolicy: Serial
  source:
    type: Git
    git:
      uri: 'http://192.168.56.150/root/simple-webapp.git'
      ref: master
  output:
    to:
      kind: ImageStreamTag
      name: 'simple-webapp-docker:latest'
  strategy:
    type: Docker
    dockerStrategy: {}
  triggers:
    - type: ImageChange
    - type: ConfigChange
    - type: Generic
      generic:
        secret: d933479692089006

Notes:

strategy.type: Docker specifies the Docker build strategy.
dockerStrategy: {} is acceptable when the Dockerfile in the repo defines the build. Add properties such as forcePull if needed.
The output.to image stream tag must exist (or be creatable) in the project before the BuildConfig can start a build.

Create the ImageStream for the output

If the BuildConfig refers to an ImageStreamTag that doesn’t yet exist (e.g. simple-webapp-docker:latest), the web console may show an error like “invalid output reference” when you try to import the BuildConfig YAML. Create the ImageStream first. Minimal ImageStream YAML:

apiVersion: image.openshift.io/v1
kind: ImageStream
metadata:
  name: simple-webapp-docker
  namespace: my-webapplication

Import or create the ImageStream in the console (Add to Project → Import YAML/JSON → paste YAML → Create) or apply it with oc apply -f imagestream.yaml.

A screenshot of the OpenShift Origin web console showing a modal dialog that says "Image stream simple-webapp-docker has been imported." The dialog displays import results and a link to continue to the project overview.

Start the build

Once the ImageStream exists and the BuildConfig is applied, start the build manually or wait for a webhook/trigger:

oc start-build simple-webapp-docker -n my-webapplication

Watch the build logs in the console or with:

oc logs -f bc/simple-webapp-docker -n my-webapplication

The logs should show Docker build steps executed by OpenShift. When the build finishes successfully, the image will be pushed to the simple-webapp-docker:latest ImageStreamTag and can be consumed by DeploymentConfigs or other resources.

Troubleshooting

Error importing BuildConfig: create the referenced ImageStream first.
Docker builds failing: verify the repository contains a valid Dockerfile and the Dockerfile path matches spec.source.contextDir if used.
Image pull or push permission issues: ensure the project has permissions and the internal registry is reachable.

Links and references

OpenShift Builds overview: https://docs.openshift.com/container-platform/latest/builds/understanding-builds.html
OpenShift BuildConfig API: https://docs.openshift.com/container-platform/latest/rest_api/build_apis/buildconfig-build-openshift-io-v1.html
oc CLI reference: https://docs.openshift.com/container-platform/latest/cli_reference/openshift_cli/getting-started-cli.html

This process lets you convert an existing Source (S2I) BuildConfig into a Docker strategy BuildConfig with minimal YAML changes and the required ImageStream in place.

Introduction

Pre-Requisite - Docker and Kubernetes

Getting Started with OpenShift

OpenShift Concepts - Projects and Users

Concepts - Builds and Deployments

Networks, Services, Routes and Scaling

Storage, Templates and Catalog

Conclusion and APPENDIX

Inspect the existing BuildConfig

Export the BuildConfig YAML and simplify it

Prepare the repository

Minimal BuildConfig using Docker strategy

Create the ImageStream for the output

Start the build

Troubleshooting

Links and references

Watch Video

​Inspect the existing BuildConfig

​Export the BuildConfig YAML and simplify it

​Prepare the repository

​Minimal BuildConfig using Docker strategy

​Create the ImageStream for the output

​Start the build

​Troubleshooting

​Links and references

Watch Video

Inspect the existing BuildConfig

Export the BuildConfig YAML and simplify it

Prepare the repository

Minimal BuildConfig using Docker strategy

Create the ImageStream for the output

Start the build

Troubleshooting

Links and references