When working with containerized applications, it’s common to target multiple platforms such as amd64 and arm64. Instead of publishing separate tags for each architecture, you can create a multi-architecture manifest (also known as an image index). This allows tools like Docker or Kubernetes to automatically pull the correct image for the host architecture.
One of the simplest ways to achieve this is by using crane, a command-line tool from Google’s go-containerregistry project.
crane index append \
-m reg.example.com/project/app:1.0.0-amd64 \
-m reg.example.com/project/app:1.0.0-arm64 \
-t reg.example.com/project/app:1.0.0 -vHere’s what happens step by step:
1. Two platform-specific images already exist in the registry: one built for amd64, the other for arm64.
2. The -m flags specify the manifests to include in the new index.
3. The -t flag defines the final multi-arch tag (1.0.0 in this case).
4. The -v flag enables verbose output, useful for debugging.
After running this command, pulling reg.example.com/project/app:1.0.0 will automatically serve the correct architecture-specific image depending on the client’s platform.
Why This Matters
• Seamless developer experience: Users don’t need to worry about which tag matches their machine.
• Kubernetes compatibility: Clusters with mixed node types (x86 and ARM) can run the same deployment manifest.
• Future-proofing: ARM-based infrastructure is growing rapidly (e.g., AWS Graviton, Apple Silicon), so multi-arch support is becoming essential.
Final Thoughts
Using crane index append is a lightweight yet powerful way to unify platform-specific images under a single tag. It fits naturally into CI/CD pipelines and ensures your container images are portable, modern, and ready for diverse runtime environments.