Skaffold vs Source-to-Image

Skaffold is Google’s open-source project for building, pushing and deploying applications. It runs client-side and has no component installed on a cluster. In development mode, it watches source files and can rebuild images, synchronize files, test images and redeploy when changes are detected. Its command-line interface can build, test, render, apply, deploy and clean application artifacts. Listed capabilities include policy-based image tagging, resource port-forwarding, logging and file syncing. Builder integrations include Docker, Jib, Bazel, custom builders, Buildpacks and ko. Deployment options include kubectl, kpt, Helm, Docker, Google Cloud Run, Kustomize and Render. Cloud Code provides extensions for Visual Studio Code and JetBrains IDEs. Skaffold supports Linux, macOS and Windows and is listed at free as an open-source project with standalone CLI and IDE integrations. It checks Google servers for updates by default, although that check can be disabled. Installation documentation says anonymized usage data is collected with an opt-out. Its gRPC server is not compatible with HTTPS.

Source-to-Image is a free, Apache-2.0 toolkit for building reproducible container images from source code. It places source in a builder image, lets that container prepare the application, and outputs a ready-to-run image. A documented workflow can build from a Git repository without a Dockerfile. Builder images may provide assemble and run scripts, plus optional scripts for saving artifacts and explaining usage. Compatible builders can reuse artifacts from an earlier output when incremental settings and scripts are supplied. A .s2iignore file filters source files and directories, while .s2i/environment defines build variables that also appear in the output image. S2I can use an OnBuild strategy with images containing Dockerfile ONBUILD instructions. Examples cover Docker, OpenShift, UBI, Ruby, and WildFly. It runs on Linux, macOS, and Windows, with Docker 1.6+ and Go 1.7.1+ listed as dependencies.