Chapter 1. Understanding image builds

OpenShift Container Platform uses Buildah to build a container image from a Dockerfile. For more information on building container images with Dockerfiles, see the Dockerfile reference documentation.

Source-to-image (S2I) is a tool for building reproducible container images. It produces ready-to-run images by injecting application source into a container image and assembling a new image. The new image incorporates the base image, the builder, and built source and is ready to use with the buildah run command. S2I supports incremental builds, which re-use previously downloaded dependencies, previously built artifacts, and so on.

The custom build strategy allows developers to define a specific builder image responsible for the entire build process. Using your own builder image allows you to customize your build process.

A custom builder image is a plain container image embedded with build process logic, for example for building RPMs or base images.

Custom builds run with a high level of privilege and are not available to users by default. Only users who can be trusted with cluster administration permissions should be granted access to run custom builds.

The Pipeline build strategy allows developers to define a Jenkins pipeline for use by the Jenkins pipeline plugin. The build can be started, monitored, and managed by OpenShift Container Platform in the same way as any other build type.

Pipeline workflows are defined in a jenkinsfile, either embedded directly in the build configuration, or supplied in a Git repository and referenced by the build configuration.