A Practical Guide to OpenShift Builds and BuildConfig
In modern application development, the journey from source code to a running container is a critical pathway. Automating and standardizing this process is essential for achieving speed, reliability, and security. OpenShift, a leading enterprise Kubernetes platform, provides a powerful, integrated toolset for just this purpose, centered around the concepts of Builds and BuildConfigs.
Understanding how to leverage these features is key to unlocking the full potential of your development workflow. This guide will walk you through the core concepts, strategies, and best practices for managing container image creation directly within your OpenShift cluster.
What is an OpenShift Build?
At its core, an OpenShift Build is the process of transforming input parameters into a runnable container image. The most common input is source code from a repository like Git, but it can also be other artifacts. The output is a new container image that is pushed to an image registry, ready for deployment.
This process is defined and controlled by a specific OpenShift resource: the BuildConfig.
The Power of the BuildConfig
A BuildConfig is a resource object that defines the entire build process from start to finish. Think of it as the recipe for creating your application’s image. It contains all the necessary instructions, including:
- Where to get the source code from.
- Which build strategy to use.
- Where to push the final container image.
- What triggers should automatically start a new build.
By defining this process in a declarative object, you ensure that every build is repeatable, consistent, and version-controlled, forming a foundational block for any robust CI/CD pipeline.
Exploring Key Build Strategies
OpenShift offers several distinct build strategies, each tailored to different development needs and workflows. Choosing the right one is crucial for an efficient setup.
1. Source-to-Image (S2I) Build
The Source-to-Image (S2I) strategy is designed to let developers focus purely on their code, without needing to write or maintain a Dockerfile. It works by combining application source code with a dedicated S2I builder image that already contains the necessary language runtime and build tools (e.g., a Node.js or Python builder).
The S2I process intelligently injects the source code into the builder, compiles it, and produces a final, optimized application image. This is an excellent choice for teams that want to standardize their build environments and accelerate development for common runtimes.
2. Docker Build
For teams that already have a Dockerfile and want full control over their image creation process, the Docker build strategy is the ideal choice. When this strategy is selected, OpenShift will use the Dockerfile located in your source code repository to build the image.
This approach provides maximum flexibility and is familiar to anyone with containerization experience. It allows you to leverage multi-stage builds and other advanced Docker features directly within the automated OpenShift build system.
3. Custom Build
The Custom build strategy offers ultimate flexibility for complex or non-standard build requirements. This strategy allows you to define your own builder image that contains all the specific logic required to produce your application image.
You might use a Custom build if your application requires proprietary compilers, involves complex multi-step processes, or needs to run specific acceptance tests before the image is finalized. You have complete control over the build environment and its execution.
4. Pipeline Build
For comprehensive CI/CD workflows, the Pipeline build strategy is the most powerful option. It leverages Jenkins (or Tekton) to execute a sophisticated, multi-step pipeline defined in a Jenkinsfile.
This allows you to orchestrate a complete workflow that includes not only building the image but also running unit tests, performing integration tests, pushing to multiple registries, and triggering deployments across different environments. This strategy is the foundation for building a complete, end-to-end CI/CD solution within OpenShift.
Automating Your Workflow with Triggers
One of the most valuable features of a BuildConfig is its ability to automatically trigger new builds based on specific events. This automation is essential for creating a seamless continuous integration flow. Key triggers include:
- GitHub/GitLab/Bitbucket Webhook: Automatically starts a new build whenever a
git pushis made to a specific branch in your repository. - Image Change: Triggers a rebuild of your application whenever a base image it depends on is updated. This is critical for automatically applying security patches from underlying images.
- Configuration Change: Starts a new build if the
BuildConfigitself is modified, ensuring changes to the build process are immediately applied.
Security Best Practices for OpenShift Builds
Building container images is a security-sensitive process. Following best practices is essential to protect your applications and infrastructure.
- Use Trusted Base Images: Always build your applications on top of official, trusted, and regularly updated base images to minimize the risk of inheriting known vulnerabilities.
- Manage Secrets Securely: Never hardcode passwords, API keys, or other credentials in your source code or
Dockerfile. Instead, use OpenShiftSecretsto securely inject them into the build environment at runtime. - Implement Image Scanning: Integrate an image scanning tool (like OpenShift’s built-in scanner or third-party solutions) into your pipeline to automatically check for known vulnerabilities (CVEs) in your final images before they are deployed.
- Apply the Principle of Least Privilege: Ensure the service account running the build has only the permissions it strictly needs to perform its tasks.
By mastering OpenShift Builds and BuildConfigs, you can create a highly automated, secure, and efficient path from code to deployment, empowering your development teams to deliver value faster and more reliably.
Source: https://kifarunix.com/openshift-builds-and-buildconfig-essentials-guide/
