Migration Best Practices and Checklist

Chainguard Container Images are designed to be minimal and to include special features for increased security and provenance attestation. Depending on your current base image and customizations, you may need to make some adjustments when migrating your current workloads to use Chainguard Container Images. This checklist provides a high-level overview of the steps you should consider when migrating to Chainguard Container Images. A PDF version of this checklist is available for download here.

Important to Know

• Most Chainguard Container Images don’t have a package manager or a shell by default. These are distroless images intended to be used as slim runtimes for production environments.
• For every version of an image, a complimentary standard image is provided with a shell and the apk package manager. These are identified by the -dev suffix and can be customized.
• When possible, we recommend using multistage builds that combine a build stage based on a -dev variant and a runtime stage based on a distroless image.
• Chainguard Container Images typically don’t run as root, so a USER root statement may be required before installing software.
• Chainguard Container Images are based on apk. If you’re coming from Debian or Ubuntu you’ll need to replace apt commands with their apk equivalents. This also applies for other distros that are not based on apk.
• Some images may behave differently than their equivalent in other distros, due to differences in entrypoint and shell availability. Always check the image documentation for usage details.

Migration Checklist

• Check the image’s overview page on the Images Directory for usage details and any compatibility remarks.
• Replace your current base image with a standard -dev (such as latest-dev) variant as a starting point.
• Add a USER root statement before package installations or other commands that must run as an administrative user.
• Replace any instances of apt install (or equivalent) with apk add.
• Use apk search on a running container or the APK Explorer tool to identify packages you need – some commands might be available with different names or bundled with different packages.
• When copying application files to the image, make sure proper permissions are set.
• Switch back to a nonroot user so that the image does not run as root by default.
• Build and test your image to validate your setup.
• Optional: migrate your setup to a multi-stage build that uses a distroless image variant as runtime. Our Getting Started with Distroless guide has detailed information on how to work with distroless images and multi-stage builds.

For detailed migration guidance, please refer to our Migration Docs on Chainguard Academy. For troubleshooting, check our Debugging distroless Images resource.